Selective catalytic reduction of aromatic nitro compounds and hydrocarbons: monograph 9786010434417

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AL-FARABI KAZAKH NATIONAL UNIVERSITY

Y. A. Aubakirov, L. R. Sassykova

SELECTIVE CATALYTIC REDUCTION OF AROMATIC NITRO COMPOUNDS AND HYDROCARBONS Monograph

Almaty «Qazaq university» 2018

UDC 665.6+66.097+541.128:665.658.2+665.654.2+ 665.664.4+661.183.6+66.095.217+66.095.253.7 LBC 24.235, Л61я73, Г23я73-1 A 80 Recommended for publication by the decision of the Academic Council of the al-Farabi KazNU (Protocol № 9 dated 30.04.2018) and RISO of the al-Farabi KazNU (Protocol № 6 dated 04.05.2018) Reviewers: Doctor of Chemistry, Professor B.S. Selenova Doctor of Chemistry, Professor S.M. Tazhibayeva

Aubakirov Y.A., Sassykova L.R. A 80 Selective catalytic reduction of aromatic nitro compounds and hydrocarbons: monograph / Y.A. Aubakirov, L.R. Sassykova. – Almaty: Qazaq university, 2018. – P. 338. ISBN 978-601-04-3441-7 In the monograph questions of reduction of aromatic nitro compounds and hydrocarbons for producing valuable intermediate and final products are considered. Catalytic hydrogenation at atmospheric and elevated hydrogen pressures is described in detail. The literature and patent data as well as the results of own studies of the authors are presented. A comparative analysis of the mechanisms of hydrogenation of aromatic nitro compounds and hydrocarbons of various authors is given. For the convenience of the reader the monograph contains a detailed glossary and necessary illustrative material. The monograph is intended for researchers working in the field catalysis, fine organic synthesis, chemical technology of organic substances, oil refining and petrochemistry; bachelors, masters and doctoral students studying in the сhemistry specialties. Publishing in authorial release

UDC 665.6+66.097+541.128:665.658.2+665.654.2+ 665.664.4+661.183.6+66.095.217+66.095.253.7 LBC 24.235, Л61я73, Г23я73-1 ISBN 978-601-04-3441-7

© Aubakirov Y.A., Sassykova L.R., 2018 © Al-Farabi KazNU, 2018

TERMS AND ACRONYMS AB Abs ACHOL p-ADA AD AEC AH AHM AN 4-ANT AO AOB p-AP APG p-ATSA AVT BFLH (or WFLH) BMOs BO CDA CHA p-CHNB CHT CNM DACH DADB DAS 2,4-DAT DA DDs °С Des DMF DNDB DNS DNT 2,4-DNT 2,6-DNT EA EB EDP GED GHG GFM GPP

– Azobenzene – Absorption – Aminocyclohexanol – p-Aminodiethylaniline – Aromatic Derivatives – Atomic Electric Charge – Aromatic Hydrocarbons – Advanced Huckel Method – Aniline – 4-Amino-2-Nitrotoluene – Atomic Orbitals – Azoxybenzene – p-Aminophenol – Associated Petroleum Gas – p-Aminotoluenesulfonic Acid – Atmospheric-Vacuum Tube – Broad (Wide) Fraction of Light Hydrocarbons – Binding Molecular Orbitals – Boundary Orbitals – Color Developing Agent – Cyclohexylamine – p-Chloronitrobenzene – Catalytic Hydrogen Transfer – Carbon Nanomaterials – Diaminocyclohexane – Diaminodibenzyldisulphonic Acid – 4,4’-Diaminostilbene-2,2’-Disulfonic Acid – 2,4-Diaminotoluene – Diethylenetriamine – Diphenyl Derivatives – Degree Celsius – Desorption – Dimethylformamide – Dinitrodibenzyldisulphonic Acid – 4,4’-Dinitrostilbene-2,2’-Disulfonic Acid – Dinitrotoluene – 2,4-Dinitrotoluene – 2,6-Dinitrotoluene – Ethylenediamine – Ethyl Benzene – Electrical Desalting Plant – Gas Electron Diffraction – Greenhouse Gases – Glass-Fiber Materials – A Gas Processing Plant

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GTL FCC FGO FL 4-HA-2-HT HAPs HB HC HF HOAO HPK IL IR Spectroscopy K KPO LG LMOs MAC (MPC) Substances In The Air MMOs MO MNT MSC m-NA p-NA NB NBMOs ND p-NDA o-NP p-NP NSB PAHs PES m-PhDA PHA PhDA PM p-NT PVA PVM QSPR REE RGO RI RSPM SHHRM

– Gas-to-Liquid Technology – A Fluid Catalytic Cracking – Functionalized Graphite Oxide – Flammable Liquids – 4-Hydroxylamino-2-Nitrotoluene – Hazardous Air Pollutants – Hydrazobenzene – Hydrocarbons – Hartree-Fock Method – Highest Occupied Atomic Orbital – High-Pressure Kinetic Unit – Ionic Liquid – Infrared Spectroscopy – Degree Kelvin – Karachaganak Petroleum Operating – Liquefied Gases – Loosening Molecular Orbitals Molecular Orbitals – The Maximum Allowable (Permissible) Concentrations of – The Method of Molecular Orbitals – Molecular Orbitals – Mononitrotoluene – Metal Supported Catalyst – meta-Nitroaniline – para-Nitroaniline – Nitrobenzene – Non-Binding Molecular Orbitals – Nanodiamonds – p-Nitrodiethyl Aniline – ortho-Nitrophenol – para-Nitrophenol – Nitrosobenzene – Polynuclear Aromatic Hydrocarbons – Potential Energy Surfaces – m-Phenylenediamine – Phenylhydroxylamine – Phenylenediamine – Particulate matter – p-Nitrotoluene – Polyvinyl Alcohol – Paint and Varnish Material – Quantitative Structure – Property Relationship – Rare Earth Elements – Reduced Graphene Oxide – Method of Reactivity Indexes – Respirable Suspended Particulate Matter – Solid and Heavy Hydrocarbon Raw Materials

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TA Tamb TDI TLC TNT TOF TPD TPP TPR TPSR TTB UNEP UNFCCC VOCs WHO XAS

– Triethylenetetramine – Ambient Temperature – Toluene Diisocyanate – Thin Layer Chromatography – Trinitrotoluene, Trotyl – Turnover Frequency – Temperature-Programmed Desorption – Thermal Power Plants – Temperature-Programmed Reduction – Temperature-Programmed Surface Reaction – Temporary Technological Bundle – United Nations Environment Program – United Nations Framework Convention on Climate Change – Volatile Organic Compounds – World Health Organization – X-ray absorption spectroscopy

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INTRODUCTION    The reduction of nitro compounds to amines is a very significant stage in the process, which probably can be considered the most important process in the chemistry of aromatic compounds. Currently, one of the topical areas is the development and investigation of highly efficient and selective catalysts for the hydrogenation of aromatic nitro compounds to the corresponding amines, since amines find wide application in the production of various dyes, drugs, corrosion inhibitors, stabilizers, polyurethanes, antiknock additives for gasolines and motor fuels and others. The processes of hydrogenation of aromatic hydrocarbons are the most important in multitone organic technology. Hydrogenation of aromatic hydrocarbons provides a wide range of different compounds, such as cyclohexane (for example, of the benzene produced in the world, about 20% is used to produce cyclohexane) and its derivatives, cyclohexylamine, tetralin, decalin through the attachment of hydrogen via the double bonds of aromatic rings. The production of cyclohexane is increasing every year since it can be used to produce caprolactam, adipic acid and cyclohexanol. Hydrogenation of naphthalene produces such technically important products as tetralin and decalin. Tetralin is used in the production of β-naphthol, as well as as a solvent for varnishes and paints. Decalin is used in the synthesis of a number of drugs and as a highly effective solvent. Hydrogenation of aromatic hydrocarbons is an important petrochemical process, which aims, in particular, to improve the quality of fuels, due to stricter environmental standards for the content of aromatic compounds. The importance of the processes of hydrogenation of aromatic hydrocarbons is difficult to overestimate these days, as one of the requirements that dictates the transition to high quality motor fuel (Euro-4, Euro-5, Euro-6) is associated with a significant reduction in the content of aromatic hydrocarbons in them. Since at present the demand for quality transport fuels is growing rapidly, the deep hydrogenation of gasoline and diesel fuels to reduce aromatic hydrocarbons is an important role in the world.

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In many cases, various products of refineries contain aromatic hydrocarbons with significant concentrations. For such fractions, additional processing is required to produce petroleum products with the satisfactory characteristics and properties. It is well known that reducing the content of aromatic hydrocarbons contained in diesel fuel or their complete removal from the composition can increase the cetane number and improve the maximum value of the non-smoking fuel flame. In addition, when removing aromatic hydrocarbons, it is possible to improve the viscosity properties of the solvent and lubricating oils. In the monograph questions of reduction of aromatic nitro compounds and hydrocarbons for producing valuable intermediate and final products are considered. Catalytic hydrogenation at atmospheric and elevated hydrogen pressures is described in detail. The subject of the monograph offered to the reader is relevant from the scientific and applied point of view. The monograph is prepared on the problem of synthesis of valuable products and intermediates for the preparation of various dyes, drugs, corrosion inhibitors, stabilizers, polyurethanes, antiknock additives for gasoline and motor fuels, etc. The data described by the authors on theoretical issues (adsorption, quantum chemical description of reactivity molecules, the mechanisms of reduction, the electronic state of metals, the chemistry of the processes of conversion of aromatic nitrocompounds and hydrocarbons) and practical (hydrogenation technology, special equipment) are very relevant. A comparative analysis of the mechanisms of hydrogenation of aromatic nitro compounds and hydrocarbons of various authors is given. The monograph is compiled on the basis of an analysis of domestic and foreign literature with a depth of 50 years. The manuscript also describes the results of the authors's own experimental data, summarized for many years of experience in conducting catalytic reduction of aromatic nitrocompounds and hydrocarbons. In the monograph references for convenience are given to each part of the monograph. The monograph contains a detailed glossary and necessary illustrative material. The monograph is intended for researchers working in the field of catalysis, fine organic synthesis, chemical technology of organic substances, oil refining and petrochemistry; bachelors, masters and 7

doctoral students studying in the specialties “Chemistry”, “Petrochemistry”, “Chemical Technology of Organic Substances”, students, undergraduates and doctoral students, when studying disciplines “Technology of processing natural and oil associated gas”, “Technology of oil, gas and coal”, “Modern aspects of petrochemistry”, “Technologies for processing natural, oil associated and technological gases”, “Modern technologies of oil, gas and coal”, “Syntheses based on liquid and solid hydrocarbons of oil origin”, “Chemistry and physics of oil, gas and coal” “Structure of matter”, “Theory and technology of catalytic petrochemical productions”. The majority of points of the monograph is written taking into account curricula of above-mentioned disciplines.

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Part I. THE CATALYTIC REDUCTION OF AROMATIC NITRO  COMPOUNDS    Chapter 1. Aromatic nitrocompounds 1.1. Typical representatives of aromatic nitro compounds, properties Nitro compounds are derivatives of hydrocarbons of the general formula R-NO2 having in their composition a nitro group directly linked to an aliphatic or aromatic radical [1]. Depending on the nature of the hydrocarbon radical “R”, nitro compounds are divided into aliphatic and aromatic. The simplest representative of nitrocompounds of the aliphatic series is nitromethane, chemical compound with the formula CH3-NO2 (fig.1).

a

b

Figure 1 – Molecule of nitromethane

Aliphatic nitro compounds are divided into primary, secondary and tertiary (fig. 2).

Figure 2 – Aliphatic nitro compounds: a – primary, 1-nitropropane; b – secondary, 2-nitropropane; c – tertiary, 2-methyl-2-nitropropane

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Aromatic nitrocompounds (fig.3) are a group of organic substances, headed by nitrobenzene (fig.3a, fig.4) and formed from benzene and its homologues (toluene and xylene), naphthalene and anthracene by replacing one or more atoms with a nitro group. In aromatic nitrocompounds, the nitro group is bound to the aromatic ring. The nitro group can be replaced, along with halogen and some alkyl radicals, in almost any place of the ring [2].

Figure 3 – Aromatic nitro compounds of different structure: a – nitrobenzene, b – 2,4,6-trinitrophenol (picric acid), c-1-nitronaphthalene.

Figure 4 – Nitrobenzene

Compounds containing a nitro group are very rare in nature, almost the only natural representative of this class is the antibiotic levomycetin (fig.5):

Figure 5 – The antibiotic levomycetin

In the nitro group there is a π-conjugation (p-π-conjugation), as a result of which both bonds become equivalent. The structure of the 10

nitro group can be represented by two equivalent mesomeric structures (or resonant structures). The nitro group is flat, some of its geometric parameters are given in the figure using the example of nitromethane (fig.6).

Figure 6 – Nitromethane

Nitro compounds that have the most important industrial significance include nitrobenzene, mono- and dinitrotoluenes, trinitrotoluene (TNT), tetryl, mononitrochlorobenzenes, nitroanilines, nitrochlorotoluenes, nitronaphthalene, dinitrophenol, picric acid (trinitrophenol), and dinitrocresol. Compounds containing several nitro groups, when heated or detonation decompose with an explosion, therefore many of them found application as explosives. Nitro groups (especially in symmetric trinitro compounds) greatly increase the ability of a carbon atom located in the ortho position to nitro groups to oxidize. Thus, trinitrobenzene (1), even under the action of weak oxidants, is converted to trinitrophenol, picric acid (2), fig.7:

Figure 7 – Transformation of trinitrobenzene to trinitrophenol

The nitro group also strongly influences the mobility of the halogen, located in the ortho- and para-positions. As the number of nitro groups in the aromatic nucleus increases, the mobility of the 11

halide increases. For example, the chlorine atom in trinitrochlorobenzene even when heated with water is easily replaced by hydroxyl (fig.8):

Figure 8 – Replacement of chlorine atom in trinitrochlorobenzene by hydroxyl: 1- trinitrochlorobenzene, 2- trinitrophenol.

1.2. Application of nitro compounds. Amines production from nitro compounds Aromatic nitro compounds are used mainly in the composition of explosives or as solvents. In general, these compounds are used to reduce the aniline derivatives used in the production of paints, pigments, insecticides, textiles, plastics, resins, elastomers (polyurethane), pharmaceuticals, plant growth regulators, fuel additives and vulcanization accelerators for rubber and antioxidants [3]. Dinitrotoluenes are used in organic synthesis, paints, explosives, and as fuel additives. Nitrotoluenes are used in the manufacture of paints, explosives, toluidines and nitrobenzoic acids. They are also used in some detergents, flotation agents and in the production of tires. Nitrotoluenes are used in the synthesis of funds from sunburn and the production of gasoline inhibitors. 2,4,6-Trinitrotoluene is a military and industrial explosive. Nitrobenzene is used in the production of aniline. It is used as a solvent for cellulose ethers and as an ingredient in polishing material for metal, polishing and shoe polishing, and also in soap. Nitrobenzene is also used for the purification of lubricating oils and for the production of isocyanic esters, pesticides, rubber products and pharmaceuticals. The most important property of the nitro group is its ability to be reduced to an amino group.

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1.3. Aromatic amines: brief information Amines are organic compounds that are derivatives of ammonia, in the molecule of which one, two or three hydrogen atoms are replaced by hydrocarbon radicals. According to the number of substituted hydrogen atoms, primary (one hydrogen atom), secondary (replaced by two atoms from three) and tertiary (all three atoms) amines are respectively distinguished (fig.9). A quaternary ammonium compound of the form [R4N]+Cl- is an organic analogue of the ammonium salt. By the nature of the organic group bonded to nitrogen, aliphatic CH3-N 90 1,2-dinitro-3,610 2-nitro-3,685 dimethoxybenzene dimethoxyaniline 2,6-dinitroaniline 30 1,2-diamino-395 nitrobenzene 2,6-dinitro-4-chloro-N30 2-Amino-6-nitro-N85 methylaniline methylaniline 2-Nitro-3,6120 1,2-diamino-3,670 dimethoxyaniline dimethoxybenzene 6-nitroindazole 60 6-aminoindazole 90 4-nitrobenzyl alcohol HCOOH 4-Amino-benzyl alcohol >95 1-nitronaphthalene 1-naphthylamine >95 4-Nitrofluorobenzene 4-aminofluorobenzene >95 2-nitrobenzoic acid 2-aminofluorobenzene >95 4-nitrobenzonitrile 4-aminobenzonitrile >95 4-chloroaniline, 4-nitrochlorobenzene, 75-95 20 H3PO2 Na3PO2 4-iodoaniline, 4-nitroiodobenzene, 604-fluoroaniline, 4-nitrofluorobenzene, 80ºС 2-chloro-o2,6-dinitrochlorobenzene, phenylenediamine, 1,3,5-trichloro2,4,6-Trichloroaniline 2-nitrobenzene

The reduction in the formic acid environment proceeds in a high yield and, as a rule, is completed within 15 min. Some examples are presented in tab.1. Formic acid is not very suitable for the reduction of compounds containing halogen in the core, except fluorine, since the hydrohalic acid formed as a result of dehalogenation blocks the catalyst (in the presence of formates, dehalogenation can be carried out even without affecting the nitro group). The reduction in HCOOH is also unsuitable for most nitro derivative heterocycles containing a sulfur atom. Effective catalysts for the reduction of the nitro group to the amino group are hypophosphoric (phosphoric acid) and its salts. When used 21

in methanol, ethanol or tetrahydrofuran, the reduction of the nitro group is not accompanied by the substitution of halogen, and halogenoanilines are formed. In polynitro compounds there is a reduction of all nitrogroups. Hypophosphates can also be used to reduce nitro compounds to hydroxylamines. The process is carried out in a two-phase system containing aqueous tetrahydrofuran. The organic solvent promotes the removal of the hydroxylamine derivative from the surface of the catalyst and thus interrupts the subsequent reduction. The yield of compounds that are difficult to obtain by other methods is from 40 to 90%. 2.2.3. Electrochemical reduction of nitro compounds Electrochemical reduction of nitrotoluenes was carried out mainly in aqueous and alcoholic media in the presence of alkali and alkali metal salts. Depending on the conditions, the process is completed at the stage of obtaining azo-, azoxy- and hydrazo derivatives. However, the electrochemical reduction of p-nitrotoluene (p-NT) in acid media leads to p-toluidine, and in the hydrochloric acid-formaldehyde system to N, N-dimethyltoluidine. Calculations performed by the method of Non-Binding Molecular Orbitals (NBMOs) allowed to find a linear relationship between the polarographic reduction potential of nitro compounds and the binding energy of vacant MOs in nitro nitrosocompounds, and also to reveal the pH (in the range from 0.5 to 9.2) by this value. Like catalytic reduction, electrochemical reduction can be accompanied by the formation of by-products. When omononitrotoluene (MNT) is reduced in a medium of 30% H2SO4 with the addition of CuSO4, 2-amino-5-hydroxytoluene is formed. Under the same conditions, 5-amino-2-hydroxytoluene was obtained from mmononitrotoluene (MNT). At the electrochemical reduction of 2,4-dinitrotoluene (DNT) in a concentrated H2SO4 medium, the reaction product is 3-hydroxy-2,4diaminotoluene, in alcoholic HCl it is 2-amino-4-nitrotoluene with impurities of diamino and azoxy compounds.

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2.2.4. Reduction by carbon monoxide and its complexes In recent years, much attention has been paid to the use of carbon monoxide (II) and its complexes for the reduction of nitro compounds, since these reactions open the way to the non-phosphogenic production of isocyanates. For the first time, the reaction of nitro compounds with Fe (CO)5 in an alkaline medium was carried out in 1925 by Farbenindustrie firm. As a reducing agent for m-nitrotoluene (MNT), iron pentacarbonyl (taken in excess of 1.4 mol/mol) in hot dibutyl ether was used. The received results are presented in tab. 2. Table 2 – Products of reduction of MNT isomers by iron pentacarbonyl Isomer

Reaction product

о-MNT

2,2'-dimethylazobenzene o-toluidine 3,3'-dimethylazobenzene m-toluidine 4,4‘-dimethylazobenzene

m-MNT p-MNT

Yield, % Melting point (Boiling point), ºС 67 55-56 13 196-198 48 52.5-53.5 6 199-201 67 142-144

Apparently from the data provided in tab.2, main products of reaction are azoderivants. For reduction of mononitrocompounds the scheme was offered (3): RNO2 → RNO → RN:Kt → RNCO

(3)

According to this scheme, a stable (with iron) or unstable (with palladium or platinum) complex with a catalyst can form at the stage of nitrene production. Since the intermediates are substantially more reactive than the original nitro compounds, the initial conversion of one of the nitro groups into an isocyanate group occurs in dinitro compounds (including dinitrotoluene, DNT) and only then the second nitro group is reduced. The reaction is carried out in an inert solvent, for example, chlorobenzene, in the presence of catalysts – platinum group metals – at high (1-15 MPa) CO pressures, as the increase in pressure speeds 23

up the process. The effect of temperature on the process is ambiguous. On the one hand, high temperatures are required to increase the reaction rate, and on the other hand, an intensive decomposition of isocyanates begins (above 200°C) (fig. 13).

Figure 13 – Dependence of the conversion of 2,4-DNT (1) and the formation of 3-nitro-4-toluylene isocyanate (2) and 2,4-TDI (3) on the reaction time at 215°C.

Some heterocyclic compounds (pyridine) catalyze the reaction, the catalyst is also activated by a number of aprotic media and is unstable and forms gum-like decomposition products that are deposited on the catalyst and delay the carbonylation. It was shown that this reaction, which proceeds at 25°C and at a pressure of 12 MPa, is efficiently catalyzed by the clusters Rh6(CO)16, Os3(CO)12, H2Os3(CO)10, Ir4(CO)12; the reducing agent is a mixture of CO and H2O [72]. 2.2.5. Reduction of nitro compounds by different reductants In this section, other reactions will be considered with the participation of compounds – “hydrogen carriers”, which, independently or under the action of catalysts, are capable of releasing hydrogen, which reduces the nitro group. Metal hydrides are widely used for the selective reduction of various groups in nitro compounds, in which the nitro group is not affected [73]. Thus, in the action of sodium borohydride in nitroquinolines, only the hydrogenation of the nucleus occurs. Widely used to increase the rate of reduction by borohydrides, LiCl additives have little effect on the reduction of the nitro group [74]. 24

The situation changes radically, if compounds of transition metals are introduced into the reaction mixture. In this case, the main products of the reduction of nitrotoluenes by sodium borohydride in the alkaline aqueous alcohol solution with the catalyst – sodium phenyltelurate are the azoxy derivatives. Azo compounds are formed mainly by reduction of nitro compounds with lithium aluminum hydride. The halides of cobalt (II), copper (II) and rhodium (III) also sharply accelerate the reduction of the nitro group by hydrides [75]. A convenient preparative method for the preparation of toluidines is the reduction of mononitrotoluene (MNT) with hydrazine or phenylhydrazine. The process is carried out at elevated temperatures (o-MNT with hydrazine hydrate at 130°C in sealed ampoules) or catalyzed by palladium in boiling methanol in the presence of KOH. As the catalyst of this reaction, complex nickel salts can also be used if the process is carried out in boiling tetrahydrofuran. m-Toluidine was obtained in high yield by boiling m-MNT with hydrazine hydrate in diethylene glycol [11, 12]. There is information about the reduction of ArNO2 by hydrazine hydrate in the presence of FeCl3 and activated charcoal. In the reaction of p-MNT in the medium of boiling methanol with hydrazine taken in an amount of ~ 1.5 moles per mole of nitro compound (at the same time, 0.1 molar portion of the activated carbon and 0.005 molar parts of FeCl3 per 1 molar part of the nitro compound), p-toluidine with 9899.5% yield was obtained [12]. When o-MNT is reduced with hydrazine hydrate in alcoholic alkali solution with ruthenium catalyst, the reaction product is 2,2’dimethylhydrazobenzene. When this reaction was carried out in a solution of sodium ethoxide without a catalyst, a mixture of toluidine and 2,2’-dimethylazoxybenzene was obtained. The reaction of nitro compounds with hydrazine hydrate is widely used in laboratory conditions for selective and exhaustive reduction of DNT. So 2,4-DNT, when reacted with hydrazine, taken in deficiency, forms mainly 4-amino-2-nitrotoluene, and with excess – 2,4diaminotoluene. The interaction of NB with hydrazine hydrate on a carbon catalyst has become the subject of a detailed study of the mechanism of reduction of nitrocompounds. When Black Pearls L grade graphite or 25

carbon was used as a catalyst, it was found that the interaction of NB and nitrosobenzene with hydrazine in boiling isopropyl alcohol leads to different reduction products. When studying the reduction of NB by deuteron-hydrazine (N2D4 D2O) under the same conditions, by NMR technics (at low conversion rates) was revealed that phenylhydroxylamine is present in the reaction products, along with the initial NB. In the reduction of 2nitro-2’-aminodiphenyl, benzo[c]cinnoline, which should be formed as a result of intramolecular cyclization, is not detected if the intermediate product is 2-nitroso-2’-aminodiphenyl. On the basis of these data, the authors concluded that nitrobenzene is not an intermediate product in the reduction of NB. It is assumed that in the catalytic process, 4 electrons transfer directly, leading directly to phenylhydroxylamine. Since hydrazine is a two-electron donor (it turns into diimide NH = NH), the authors believe that carbon plays a role in this process not only as an adsorbent, on the surface of which a nitro compound and hydrazine are located, but also an electron carrier from the second hydrazine molecule [11, 12]. The rate of reduction is practically independent of the nature of the substituent in the NB molecule (decreases only by a factor of 1.5 in the transition from p-nitro-trifluoro-methylbenzene to p-nitroaniline) and is determined by the rate of oxidation of hydrazine on the surface of the catalyst [76]. Of undoubted interest is the reaction of reduction of nitrocompounds by secondary alcohols. In the work [77] the reduction of nitrotoluenes was carried out with cyclohexanol in the presence of RhCl(CO)(PPh3) and CH3COOK. The yield of m- and p-toluidine is quantitative; 3 moles of cyclohexanone are simultaneously formed. As reductants for the synthesis of azo compounds from nitro compounds, ethylene glycol and other glycols can be used, the catalyst of this reaction is naphthoquinone. A considerable number of works is devoted to the reduction of nitrotoluenes to azo, azoxy and hydrazo compounds by amalgams of metals (magnesium, sodium). When using soft reducing agents, such as hydroxylamine in methanol, taken in a little amount (in a shortage), the process can be stopped in the nitrosocompounding step. For example, 3,4-DNT under these conditions forms a mixture of 4-nitroso-3-nitro- and 3-nitroso26

4-nitrotoluenes, 2,5-DNT – predominantly 2-nitroso-5-nitrotoluene, 2,3-DNT- 3-nitroso-2-nitrotoluene. It is noted that in the reaction with hydroxylamine in alkaline solutions, one of the nitro groups can be removed and mononitrotoluene (MNT) appears as impurities. In the last 20 years special attention is paid to studying of reduction of the aromatic nitro compounds containing other substituents, capable to reduction. Thus, it was found that sodium sulfide, used to reduce the nitro group in the nucleus, does not reduce the nitro group of the side chain. For the reduction to amines of nitrocompounds having double and triple bonds or cyano and formyl groups in the side chain, it is recommended to use electrochemically produced nickel [78]. LITERATURE to Part I 1. Чекалин М.A., Пассет Б.В., Иоффе Б.А. Технология органических красителей и промежуточных продуктов. Л.: Химия, 1980. 471 с. 2. https://ru.wikipedia.org/wiki/Нитросоединения 3. http://chem21.info/info/667763/ 4. Чарушин B.Н. Химия в борьбе с инфекционными заболеваниями // Соровс. образов, журнал. 2000. – Т. 6, № 3. – С. 64-72. 5. Sasykova L.R., Masenova A.T., Bizhanov F.B. Liquid-phase Reduction of Nitroanilines // Inst org Katal Elektrokim, 1995, 3, 21-26. 6. Сасыкова Л.Р. Каталитическое восстановление моно- и динитросоединений ароматического ряда. дисс. на соиск…канд.хим.наук // Казахстан, Алматы, 1996, 223с. 7. Rafiq К. A., Mohammad K.K., Shahnaz P. Determination of nicotinamide and 4-aminobenzoic acid in pharmaceutical preparation by LC // J. Pharm. and Biomed. Anal. 2002. Vol. 29, № 4. – P. 723-727. 8. Abdullaev M.G., Klyuev M.V. 4-Acetaminophenol and 4hydroxyphenylsalicyamide synthesized by reductive of 4-nitrophenol on palladium catalysis // Pharm. Chem. J- 2005. Vol. 39, № 12. – P. 655-657. 9. Jurgen H. (ed) Encyclopedia of Industrial Chemistry, Ullmann’s, Wiley, Florida, 1985. 10. Аубакиров Е.А. Разработка методов каталитического синтеза промышленно важных аминопродуктов. автореф. дисс. на соиск…канд.хим.наук // Казахстан, Алматы, 1996, 27с. 11. Козлов А.И., Збарский В.Л. Жидкофазное восстановление ароматических нитросоединений на твердых катализаторах // Рос. хим. ж.. – 2006. – Т.L, № 4. – С. 131. 12. Збарский В.Л., Жилин В.Ф. Толуол и его нитропроизводные // М.: Эдиториал УРСС, 2000. – 272 с.

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44. Клюев M.B. Каталитический синтез ароматических и жирноароматических аминов // В кн. Органические реагенты и товары бытовой химии на основе нефтехимического сырья, Уфа:УНИ, 1983, с. 9. 45. Клюев М.В. Влияние заместителя в ядре на гидрирование нитросоединений в присутствии металлокомплексных катализаторов // Ж. Органической химии. 1987. Т. 23. с. 581-585. 46. Клюев М.В. Каталитический синтез ароматических и жирноароматических аминов //В кн. Химические средства защиты растений. Т. II. Технология производства химических средств защиты растений, Уфа, 1982, с. 28-31. 47. Терешко Л.В. Синтез ароматических и жирноароматических аминов на палладийсодержащих катализаторах. Дисс.канд. хим. наук. Иваново. 1990. 163с. 48. Кочетова Л.Б., Клюев М.В. Механизм гидрирования нитробензола: квантово-химический подход // Нефтехимия. 1997. Т.37. №5. С. 420-426. 49. Волкова Т.Г., Клюев М.В. Гидрирование нитрохлорбензолов: влияние строения субстрата на скорость и селективность реакции // Нефтехимия. 1997. Т. 37. №4. С. 321-325. 50. Сокольский Д.В. Механизмы каталитической гидрогенизации и оптимизация катализаторов гидрирования // В кн. Механизм катализа, ч. 1. Новосибирск. Наука. 1984. с. 87-101. 51. Алмабеков О.А., Масенова А.Т., Сасыкова Л.Р., Бижанов Ф.Б. Каталитический синтез красителей для шерсти // Сб. «Наука, техника, технология». Сб.трудов Инж. Акад.наук НТИЦ, «ЛЕГПРОМ», Алматы, 1993, с.66-68. 52. Алмабеков О.А., Масенова А.Т., Сасыкова Л.Р., Бижанов Ф.Б. Восстановление нитроароматических соединений в синтезе полупропродуктов для анилилиновых красителей // Сб. «Наука, техника, технология». Сб.трудов Инж. Акад.наук НТИЦ, «ЛЕГПРОМ», Алматы, 1993, с. 69-71. 53. Bizhanov F.B., Sasykova L.R., Masenova A.T. The catalytic reduction of o-nitrophenol on 4%Pd/Al2O3 catalyst in a liquid phase // Изв.НАН РК, сер.хим., 1995, 1, p.50-54. 54. Гошин М.Е.Гидрогенизационный синтез и модификация замещенных анилинов и тетрагидрохинолинов. дисс. на соиск…канд.хим.наук // Россия, Ярославль, 2005, 157с. 55. Беляев С. В. Реакционная способность соединений с кратными связями в гидрировании на палладий- и платинусодержащем ионите. дисс. на соиск…канд.хим.наук // Россия, Иваново, 2001, 123с. 56. Klyuev M.V., Vainstein E.F. Influence of the macroligand structure on catalytical properties of metal-polimer complexes // Proc. 6-th European Symp. on Organic reactivity. Louvain-la-Neuve, 1997, p. 143. 57. Klyuev M.V. Influence of swelling of palladium containing polymers on their activity in hydrogenation // Russian polymer news, 1998, V. 3, № 3, p. 27-29. 58. Насибулин А.А., Сидорова Н.В., Клюев М.В. Влияние соства бинарных растворителей на скорость гидрирования нитробензола на палладиевых катализаторах// Нефтехимия. 1990. Т. 30. №2. С. 195-197. 59. Клюев М.В. Каталитический синтез аминов гидрированием и гидроаминированием. Дисс.докт. хим. наук. М. 1991. 368 с.

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Part II. FEATURES OF CATALYTIC REDUCTION OF AROMATIC  NITRO COMPOUNDS BY MOLECULAR HYDROGEN    Chapter 3. Adsorption of nitro compounds and intermediates of their reduction on catalysts The speed of the process, and sometimes the direction of reduction, depends on many factors: the nature of the catalyst metal, the nature and surface of the catalyst carrier, the hydrogen pressure, the temperature, the nature of the solvent, and etc. Any catalytic process (and catalytic reduction of nitro compounds also) represents set of catalytic reactions on the surfaces of the catalyst with processes of a supply of reagents into a reaction zone, and removal of products of reaction. The catalysis process on solid porous catalysts consists of the following elementary steps: 1. Diffusion of reactants from the center of the flow to the surface of the catalyst grains; 2. Diffusion of the reagents in the pores of the catalyst grain; 3. Activated adsorption (chemisorption) on the surface of the catalyst with the formation of surface chemical compounds – activated complexes “reagents-catalyst”; 4. Rearrangement of atoms with the formation of surface complexes “product-catalyst”; 5. Desorption of the product from the surface; 6. Diffusion of the product in the pores of the catalyst grain; 7. Diffusion of the product from the surface of the catalyst grain to the center of the flow. One of the main tasks of catalysis and theoretical organic chemistry is the determination of the effect of the chemical structure of compounds on the reaction rate, for example, the addition of oxygen or hydrogen to them. It is known that in the heterogeneous catalysis a chemical reaction is preceded by the adsorption stage [1, 2]. The majority of the latest advances in the field of a theoretical catalysis is related to a research of molecular composition and their adsorption on the surface of the catalyst. Today the relationship 33

between structure of the adsorbed molecules and chemistry of coordination compounds, chemistry of complexes of the transitional metals which are the active components of catalytic systems for different reactions does not raise any doubts. Adsorption of hydrogen and organic compounds on the surface is strongly correlated with the energy of the bond between them and the catalyst. The greater the free energy of the metal surface, about which it is possible to judge from the heat of sublimation, the greater the binding energy of Me-H and Me-ArNO2. The heat of sublimation decreases with the increase in the atomic number of the metal within the same period: from Fe to Ni, from Ru to Pd, from Os to Pt. At the same time, the heat of adsorption increases. It is noted that the heat of adsorption of hydrogen palladium is closer to nickel than to platinum (tab.3). With respect to the Me-H bond energy, the catalysts can be arranged in the series Pt> Ni> Pd> Rh> Os. Comparative data of the basic metals-catalysts are presented in tab. 3. Absolute activity of catalysts correlates with the amount of hydrogen sorbed by them, so the adsorption of hydrogen on the surface of various catalysts has been studied in particular. Table 3 – Thermodynamic characteristics of a number of metals

Metal Nickel Palladium Platinum

Change of a heat of The binding Work Atomization absorption in process energy of H2 function of Heat, with the surface, of metal saturation electron, eV kJ / mol kJ / mol with Hydrogen, kJ/mol 5.0 340 247-222 63-13 5.1 377 243-235 59-34 5.3 566 260-226 84-17

During reduction, hydrogen is in the form of a surface-adsorbed and dissolved in the volume of the catalyst. Hydrogenation of various compounds with respect to the structure of the reducible compounds can involve both forms of hydrogen. The state of hydrogen chemisorbed on the surface of the catalyst depends on the chemical composition of the latter, the degree of its dispersion, the hydrogen pressure, the temperature, the nature of the solvent, the structure of the double electrical layer, and etc. [3]. 34

The chemical nature of the catalyst has the strongest effect. The surface of the catalyst is heterogeneous, as evidenced by significant changes in the heat of adsorption as the metal is saturated with hydrogen (see tab.3). The minimum difference is observed in palladium, which indicates a greater homogeneity of its surface. The quality of the metal surface can be judged from the content of the fraction of centers with a low activity in the adsorption of hydrogen. The more such centers, the greater the proportion of adverse reactions: destruction, changes in the carbon skeleton, etc. At negative temperatures, the most active surface centers participate in the adsorption, and hydrogen is covalently bound to the metal in the resulting structure. It is noted the presence of a significant ionic component in these hydrides, which allows us to speak about the participation of positively and negatively charged hydrogen atoms in the process of reduction. The proton is located on the outer surface of the metal, hydride-ion – in the near-surface layers. It is stated that palladium, unlike other metals of group VIII, sorbs hydrogen inside the structure to form hydrides. Chemisorbed hydrogen can differ significantly in binding energy with a surface that is quantitatively characterized by the rate of desorption. The stronger hydrogen is held by the metal, the lower its activity in the reduction reactions. The use of mixed catalysts based on Group VIII metal alloys makes it possible to change the energy state of adsorbed hydrogen and to regulate the quantitative ratio between its various chemisorbed forms. The addition of additives to nickel can significantly increase the capacity of hydrogen (by 50 times with the addition of rhenium). The adsorption process is strongly influenced by the acid-base properties of the surface of the catalyst and the compound to be reduced. Due to their interaction in part, and sometimes completely, hydrogen is displaced from the surface. Highly polar compounds strongly influence the adsorption of hydrogen. The excess of oxygen not only completely removes the hydrogen present in the catalyst, but also deactivates the catalyst, which ceases to be pyrophoric. The absence of a correlation between the reaction rate and the content of strongly retained hydrogen during the reduction of the NB on the PdIr/Al2O3 catalyst indicates the participation in the process of hydrogen adsorbed on various parts of the surface.

35

When the molecule of nitrocompounds is reduced, the surface of the catalyst is occupied and electrons are removed from it, forming radical anions. The latter are able to pass into the solution and react with any form of hydrogen on the surface of the catalyst, as well as with the hydrogen ion in the solution. The displacement of the ionization potential of the catalyst (ΔE) in the course of chemical transformations occurring on its surface reaches 0.5-0.6 V. For hydrogenation in solutions, the activation energy is related to the change in the ionization potential under the reaction Еactivation=∆Е·23+а,

(4)

where ∆Е is potential change (it is associated with an electron work function), а is a constant, depending on the acid-base interaction on the surface [4]. Speed of hydrogenation of nitro compounds decreases in a series Pd>Pt>Rh>Ni>Ru. For Pt and Ru, ΔE is 200-220 mV, which means that the nitro compound displaces almost all of the atomically adsorbed hydrogen from the surface. The rate of the process is limited by the stage of hydrogen adsorption. Hydrogenation on Ni, Pd, Rh ΔE = 120-140 mV, hydrogen is present in a relatively large amount, but the surface is not saturated with it. When studying the effect of hydrogen pressure on the process speed, it was shown that it increases linearly with increasing pressure and, consequently, the adsorption of hydrogen is also the limiting stage. A similar conclusion was also drawn from the data on the electrical conductivity of the catalyst. For Pd, Ru – the reaction rate reaches a maximum value at 1.0 MPa and above this value does not depend on the adsorption of hydrogen. The displacement of the ionization potential of the catalyst (nickel on bentonite clay) with respect to the saturated calomel electrode upon reduction is symmetrical to the σ-Hammett constants. A proportionality is observed between the displacement of the potential in the course of hydrogen absorption and the rate of the chemical reaction (for 1,3-dinitrobenzene, ΔE-140 mV, the hydrogen absorption rate is 11.8 ml/min, for p-MNT ΔE-75 mV and 8.5 ml/min.) [4, 5]. 36

However, such regularities are not found by all researchers. It is also shown that the reaction rate increases with the growth of the effective negative charge on the nitro group, and the effective activation energy is linearly dependent on the energy of the NonBinding Molecular Orbitals (NBMOs) of the nitro compound. Since the limiting stage is associated with electron transfer, the reaction temperature coefficient is close to zero. During the reduction, the pH of the system increases as a result of the formation of an amine (in the production of aniline, the pH rises from 7 to 11), while the reaction rate depends little on this parameter. In stationary processes with a catalyst based on metals of the platinum group, the degree of filling the surface with hydrogen is close to 0.5, and the activities of palladium and platinum are close to each other. At a high degree of filling the surface with hydrogen, platinum is more effective than palladium. Substituents in any organic molecule, in particular, in the molecule of the aromatic nitro compound, directly influence both the distribution of the electron density and the adsorption of the compound on the surface of the catalyst. Depending on the type of substituent, the adsorption capacity of the nitro compound can either decrease or increase, and as a result, on the surface of the catalyst the ratios between the reagents on the surface of the catalyst will vary [7]. The adsorption of nitroarenes in liquid-phase hydrogenation processes occurs on the surface of a catalyst on which hydrogen and a solvent are already present [8, 9]. This causes the competing and displacing nature of the adsorption of the reactants and the solvent. At the same time, in a number of studies [9-15] it has been shown that the adsorption of nitro compounds on the surface of metals in solution does not depend on the adsorption of hydrogen. The patterns of interaction of substrates with the surface of the catalyst are determined by their structure, energy and symmetry of the boundary molecular orbitals (MO) of adsorbate and atomic orbitals (AO) of surface metal atoms [16]. Adsorption can occur due to the formation of hydrogen, donoracceptor bonds, or in the form of chemisorption with the formation of an ionic or covalent bond. Molecules of nitroarenes can bind to the surface of the metal by means of two fragments: an aromatic ring and

37

a nitro group. The orientation of the molecule with respect to the surface of the catalyst is determined by the predominant interaction. Nitrobenzene (NB) is strongly chemisorbed on platinum group metals [17] and, in particular, on palladium [18]. Adsorbability changes in the series Pt> Ru> Ir> Pd> Rh> Os. Hydrogenation of NB on palladium black in a water-alcoholic medium on the surface of the catalyst produces an adsorption film of NB molecules and products of its incomplete reduction, the desorption of which into the solution is very limited [19]. It was shown in [15, 20] that when adsorbed on metals, nitro compounds, being electron acceptors, form highly polarized or ionic bonds and create a positive surface charge. At the experimental study of the adsorption of aliphatic nitro compounds and NB on Pt, Pd, and Ir in [10-12] was found that nitro compounds are adsorbed due to the nitro group to form sufficiently strong N-Me and O-Me bonds as anionic complexes. In addition, upon interaction with atomic hydrogen, semi-reduced particles are formed [10, 12]. In particular, adsorption on platinum leads to the formation of two types of adsorbed particles (I and II). Each kind of particles occupies 4 adsorption centers. In particles I, double bonds of N-O are disclosed (5):

(5)

The particle I, interacting with two atoms of hydrogen adsorbed on the surface, becomes a semi-reduced particle II (6):

38

(6)

During chemisorption, an electron is transferred from the higher occupied atomic orbitals (HOAO) of the metal to the Non-Binding Molecular Orbitals (NBMOs) of the nitro compound, which significantly decreases the binding energy of N-O [10-12, 21]. As a result of the transition of the unpaired electron to the p-orbit of the aromatic ring, the anion radicals can form during the chemisorption of NB [12, 22]. Data on the adsorption of nitroarenes on palladium are extremely limited, which is due to the difficulties that arise from the experimental study of these processes [23]. Additional information is provided by quantum chemical calculations. The quantum-chemical modeling of hydrogenation of 2,4-dinitrotoluene, m-dinitrobenzene and products of their incomplete reduction (hydroxylamine and amino derivatives) on palladium was carried out in paper [24] by the Hartree-Fock method (HF). Simplified molecular models, including small metal clusters, were investigated. For the substrate and each hydrogenation product, three options for orientation on the surface of the catalyst were considered, in which the reaction was carried out via a benzene ring or one of the nitro groups. The authors conclude that binding due to nitro groups predominates in the case of 4-hydroxylamino-2-nitrotoluene and 2hydroxylamino-4-nitrotoluene, due to spatial difficulties, whereas the 3-hydroxylaminomonitrobenzene molecule is adsorbed on the Pd6 cluster by the hydroxylamine group. The distance between the surface of the cluster and the benzene ring is > 0.3 nm, and the angle between their planes is 13.5°; however, with a high filling of the catalyst surface, this angle can increase. It has been experimentally established that NB is adsorbed on the surface of platinum by oxygen atoms of the nitro group [25]. The 39

results of the simulation carried out in [24] do not contradict these data. The same orientation of NB for adsorption on the surface of iron is shown by quantum-chemical calculation [26]. At the same time, according to the experimental data [11, 12], the most reactive with respect to hydrogen is NB adsorbed on the metal surface due to the nitrogen atom. Reducing the nitro group, according to scheme of GaberLukashevich occurs in several stages. Intermediate products of hydrogenation of nitrobenzene (NB) are: nitrosobenzene (NSB) phenylhydroxylamine (PHA), azoxybenzene (AOB), azobenzene (AB) and hydrazobenzene (HB) [27]. Data on the adsorption of intermediate products of reduction in the literature are very limited, however, the available data indicate that these compounds are adsorbed mainly by oxygen and nitrogen atoms of functional groups. In particular, it is known that nitrosobenzene (NSB) is adsorbed in this way [26]. Azobenzene (AB), which has the N = N bond, is adsorbed, activated and participates in the chemical act by mechanisms similar to those for alkenes [28, 29], forming an adsorption π-complex, in which the d-electrons of the metal pass to Non-Binding Molecular Orbitals (NBMOs) of the substrate [30]. Phenylhydroxylamine (PHA) and aniline (AN) can also be adsorbed on the catalyst surface, but the adsorption of AN is accompanied by dehydrogenation of the amino group. On platinum in the presence of NB, the amino group is practically not adsorbed [10-12]. Thus, it can be considered proven that nitro compounds are adsorbed on Group VIII metals by nitrogen and oxygen atoms of the nitro group and create a positive charge of the surface of the catalyst. In this case, the formation of radical anions of NB is possible. Products of incomplete reduction of NB are adsorbed mainly by nitrogen and oxygen atoms of functional groups. AN in the presence of a nitro group is not adsorbed. When considering the problems of catalytic reduction (first of all, nitro compounds) with hydrogen, it is necessary to take into account the possibility of chemical interaction of the catalyst with the reducible compound. On the one hand, this leads to the formation of byproducts, on the other, to the poisoning of the catalyst. So, on a nickel catalyst, nitro compounds can oxidize a metal, turning it into an oxide. The presence of adsorbed hydrogen, as well as the simplest solvents, 40

reduces the likelihood of side reactions. This is explained, in particular, by the fact that the activation energy of hydrogenation processes on catalysts on the base of Group VIII metals is 60-90 kJ/mol, while the activation energy of the processes and the change in the carbon skeleton are about 150 kJ/mol. Strong influence is exerted by steric factors. A detailed study of the adsorption of various alcohols, which are solvents in the reduction of nitro compounds, has shown that alcohols with iso-structure have a lower chemisorption capacity than normal alcohols. Adsorption decreases with increasing number of carbon atoms [31]. When analyzing the role of adsorption in the reduction of nitro compounds in an alcohol medium, it must be taken into account that the water formed during the reaction can also be sorbed on the surface of the catalyst and its removal requires considerable energy expenditure. A comparative study of the kinetic regularities of the reduction of aromatic nitro compounds with various structure: nitrobenzene(NB), para-, ortho-nitrophenols (p-NP, o-NP), meta-nitroaniline (m-NA), para-nitroaniline (p-NA) and p-nitrodiethyl aniline (p-NDA) on Pd and Pd-Pt catalysts deposited on various carriers was investigated in [32-37]. Comparative hydrogenation of nitro compounds and nitrocompounds in a mixture with the corresponding amines (the reaction products) was studied. Authors found that the presence of the hydrogenation products (amines) having a stronger propensity to adsorption on the catalyst surface than the starting hydrogenated compounds may cause decrease of the process speed and amount of absorbed hydrogen. The ratio of the adsorption coefficients confirmed it. It was revealed that at comparative hydrogenation of nitro compounds of various structure in ethanol and isopropanol the rate decrease upon transition from nitrobenzene to nitroanilines, pnitrodiethyl aniline and nitrophenols. Hydrogenation of aromatic nitro compounds has been studied in an autoclave with a wide variation of process conditions in ethanol and iso-propanol. The shape of the kinetic curves of the reduction of mNA showed a likely strong poisoning of part of the catalyst surface by the reaction product. To confirm this assumption, experiments were carried out on the joint hydrogenation of m-NA and the corresponding amine, m-phenylenediamine (m-PhDA), the reduction product (fig. 14, tab. 4). 41

When reduction the mixture, the amount of the absorbed hydrogen is considerable much than theoretically calculated. Apparently, m-phDA, being adsorbed on the surface of the catalyst does not give the chance of access to a surface of hydrogen and the hydrogenated substance. The ratio of adsorption coefficients also shows that m-phDA has a stronger propensity to adsorption on the surface of the catalyst than the original hydrogenated compound-mNA. Thus, these studies support the assumption that a decrease in the process speed and a decrease in the amount of absorbed hydrogen can be due to the influence of the presence of the reaction product.

Figure 14 – Kinetic curves for the reduction of p-NA and mixtures with p-PhDA in an equivalent amount in isopropanol at PH2 = 1.0 MPa, T = 303 K, A3H2 = 800 cm3, q (amount of a catalyst) = 0.1 g.

In the study of the hydrogenation of p-nitrophenol (p-NP), the effect of the reaction product, p-aminophenol (p-AP), introduced into the reaction medium in an equivalent amount, was also studied, as in the case of m-NA. When the product, p-AP, is added, the reaction rate and the amount of absorbed hydrogen are reduced (tab. 5). This phenomenon is due to the blocking of the catalyst surface by the reaction product, p-aminophenol. In this case, as in the hydrogenation of m-NA in a mixture with m-PhDA, the ratio of b1 and b2 indicates a stronger adsorption of p-AP compared to p-NP. Probably, p-NP has 42

less access to the surface of the catalyst, since the surface of the catalyst is already occupied in the first seconds of the reaction by molecules of p-AP, which are quickly and easily adsorbed on the surface of the catalyst. The rate of the hydrogenation reaction of p-NP is significantly reduced in the presence of p-AP due to the poisoning of the catalyst surface by the reaction product. By the magnitude of the rate constants, taking into account the adsorption coefficients, it is seen that the reaction rate is constant, and this confirms the assumption of a zero order of p-NP reduction over the substrate. Table 4 – Reduction of m-NA and m-NA in a mixture with m-PhDA (calculated on 800 cm3 of hydrogen) in an equivalent amount at 1.0 MPa, T = 303 K, catalyst – PdCu/γ-Al2O3 (0.05 g)

No 1 2 3 4 5 6 7

Volume of Initial reaction rate W, cm3/min. hydrogen absorbed from the gas phase, m-NA m-NA+m-phDA cm3 50 75.0 25.0 100 55.0 20.0 200 35.0 8.0 300 28.0 7.5 400 26.0 6.0 600 20.0 4.0 700 17.0 3.0

The ratio of adsorption coefficients b1/b2 0. 33 0.36 0. 23 0. 27 0. 23 0.20 0. 18

Table 5 – Reduction of p-NP and p-NP (based on 400 cm3 of hydrogen) in a mixture with p-AP in an equivalent amount at 0.5 MPa, T = 600ºC, catalyst – Pd-Cu /γ-Al2O3 (0.05 g) Volume of hydrogen No absorbed from the gas phase, cm3 1 2 3 4 5

100 150 180 250 300

Initial reaction rate W, cm3/min. p-NP

p-NP+p-AP

85.0 72.0 65.0 56.0 34.0

20.0 16.0 13.5 12.0 7.7

43

The ratio of adsorption coefficients b1/b2 0.23 0.22 0.21 0.21 0.22

The data received in [33, 34, 36, 37] allow to assume the mechanism of reduction of the studied nitro compounds. At hydrogenation of o- and p-NP, presumably, in the beginning it is formed corresponding hydroxylamine derivative which immediately turns into quinoneimine. Since this process takes place in a very short period of time, this particle is difficult to detect by the GLC method. After this, the quinoid group is very quickly converted to the corresponding aminophenol. The latter reaction proceeds much more easily than the conversion of the NO2 group to the NH2 group. Under the studied hydrogenation conditions, n-HA is probably reduced according to the following scheme: p-Nitroaniline → p-Aminohydroxylamine → p- Phenylenediamine (7) К1 =0.06, К2 =0.17 In ethanol and isopropanol at comparative hydrogenation of nitro compounds of various structure decrease in the rate of reduction upon transition from NB to NA, p-NDA and NP is revealed. The studied nitro compounds on decrease in initial velocity of hydrogenation form a row: NB > p-NA > m-NA > p-NDA (p-NP) >> o-NP. A significant decrease in the rate of hydrogenation of aromatic nitro compounds in the transition in this series from nitrobenzene to nitroaniline and then to aromatic nitrophenols is probably due to a decrease in the adsorption capacity of o- and p-NP, most notably in the case of o-NP. Probably, the presence of substituents in the molecule OH-group (NP) and the NH2-group (NA) decreases the rate of reduction of nitro compounds. According to the data [38-42], the electron-donor amino groups in the molecule increase the electron density in nitro groups, and this effect manifests itself more strongly in the p-position, in comparison with the m-position.

44

Chapter 4. Quantum-chemical description of the reactivity of molecules in liquid-phase hydrogenation processes In explaining the kinetics and mechanisms of catalytic and noncatalytic reactions in recent decades, the method of reactivity indexes (RI) is widely used, suggesting the existence of a certain relationship between changes in the electronic structure of the reacting molecules and the direction or rate of the reaction [28, 43-50]. Currently, an approach involving the search for dependencies between the structure of substances and their properties is commonly called Quantitative Structure – Property Relationship (QSPR) – “quantitative structureproperty relationship”. Within the framework of this approach, IRS, quantitatively characterizing the structure and properties of substances, is called descriptors (from the English “description”). Descriptors of different levels can be found by both calculated and experimental methods. In different works the descriptors of the electronic structure were used, which include, in particular, charges on atoms, Highest Occupied Atomic Orbital (HOAO) and Non-Binding Molecular Orbitals (NBMOs), obtained by quantum chemical calculations, as well as descriptors of intermolecular interactions, among which are the experimentally determined values of the activation energy, changes in the enthalpy and entropy of the activation of the reactions, the acid dissociation constants, the permanent substituents of Hammett and Taft [51, 52]. Depending on the difference in the energies of the boundary orbitals (BO) of the reactants, the reactions are divided into charge and orbital control. The contribution of the charge and orbital factors to the change in the total energy can be estimated using the equation proposed by Klopman [53]. The terms of the Klopman equation are the electrostatic and covalent components of the total energy. In the case of a small difference in the energy levels between the occupied orbitals of the donor and the unoccupied acceptor orbitals, when the covalent component tends to infinity, and the electrostatic component is negligible, the reaction is orbitally controlled. In the opposite case, we can talk about charge control of the reaction. This approach is also applicable to liquid-phase hydrogenation reactions on heterogeneous 45

catalysts. In particular, it was shown in [28] that when hydrogenating substituted nitroarenes on platinum and palladium in alcohols, the observed rates increase with increasing energy of Non-Binding Molecular Orbitals (NBMO), and in the case of skeletal nickel, the indicated dependence has a maximum corresponding to NBMO of NB: NBMO increases the reaction rate for substrates with electrondonor substituents and decreases in the case of electron-acceptor substituents. Orbital control is also observed at hydrogenation of isomers of nitrochlorobenzene on porous nickel. At the same time, at hydrogenation on the put palladic catalysts charging control of reaction is observed [43-45, 54]. This agrees with the data of [55, 56], in which a relationship between the electron density at the nitro group and the rate of reduction was found for a number of substituted nitro compounds. In order to test the adequacy of the use of quantum chemical characteristics for the quantitative evaluation of the reactivity of substituted benzenes, the effective charges on C and H atoms at the 3and 4-positions of the aromatic ring of 40 monosubstituted arenes were compared [51, 57] and the σ-constants of the substituents in the reference literature [54, 58]. The resulting linear dependences with correlation coefficients of not less than 0.95 indicate the possibility of using calculated values of charges on atoms as descriptors of the electronic structure of monosubstituted benzenes. The linear correlations of σ-constants with charges on nitro groups of 2-, 3- and 4-substituted nitroarenes (equations 8-10), which are obtained in [59], also indicate the same: ortho-σ = (1.81 ± 0.10) + (12.37 ± 0.79) × q (NO2) n = 6 r = 0.99 (8) meta-σ = (14.30 ± 1.03) + (24.38 ± 1.78) × q (NO2) n = 13 r = 0.97 (9) para- σ = (9.88 ± 0.91) + (16.65 ± 1.54) × q (NO2) n = 13 r = 0.95 (10) For testing approaches utilized to further describe the reactivity of the nitro compounds and products of incomplete reduction in hydrogenation, as a model was used well-studied hydrogenation reaction of alkenes [60]. The basis for this was the analogy in the kinetic regularities of liquid-phase hydrogenation of the C = C bond 46

in alkenes and the H = N bond in azobenzenes [29], which are intermediates for the reduction of nitrobenzenes. It was shown that the rate of hydrogenation is related to the charge characteristics of the substrates: a decrease in the charge on the carbon atoms of the double bond of cycloalkene is reflected in a decrease in the reaction rate. The quantum-chemical calculations of cycloalkenes and intermediate complexes of a substrate with a catalyst [60] made it possible to confirm and refine the known mechanism of hydrogenation of alkenes [30, 61] at the Wilkinson complex, and to reveal the limiting stage of the reaction. Analysis of the quantum-chemical characteristics calculated in [51, 60] nitroarenes and kinetic data of their hydrogenation on heterogeneous catalysts showed that on a 1% Pd/C catalyst the cerium complex with nitrilotrimethylphosphonate [62] tends to increase the reaction rate with a decrease in the negative charge on the nitro group and with a decrease in NBMOs energy, the latter dependence for electron-donating and electron-withdrawing substituents is the same. On Ni/Cr2O3 and 1% Pd/Al2O3 catalysts [63], as well as on Raney nickel [64], there are reverse trends: the reaction rate increases with increasing negative charge on the nitro group and with an increase in NBMOs energy. The structural characteristics of the molecules change little when the substituent and its position in the benzene ring are changed, but there are tendencies to some increase in the reaction rate with an increase in the r (N-O) bond length are observed, at the same time it is impossible to speak about correlative dependences in this case. It should be noted the tendency to increase the reaction rate with an increase in the NBMOs energy, which agrees with the data [28]. The orbital characteristics of the molecules – the contribution of the 2pz-AO of the nitrogen atom in NBMOs (C2pz(N)2) and the population of 2pz-AO nitrogen (f2pz(N)) practically do not affect the hydrogenation rate. The negative charge on the nitro group is slightly larger for 4-nitro compounds and slightly less for the corresponding 3isomers. When introduction to the 4-position of the aromatic ringelectron acceptor substituent negative charge on the nitro group is reduced, and when administered electron – increases. There is a tendency to an increase in the relative hydrogenation rate, W with an

47

increase in the absolute value of the charge on the nitro groups of the q (NO2) substrates. By increasing the negative charge on the nitro group as a whole, the charge on the nitrogen atom of q (N) becomes more positive, and between q (N) and lg W for both catalysts also tend to linearity. It should be noted that the increase in the rate of hydrogenation with increasing negative charge on nitro groups was established in [65] for the hydrogenation of 2-substituted nitroarenes, as well as isomeric nitrochlorobenzenes. Comparing the quantum chemical characteristics of solvate complexes of 2-, 3- and 4nitrochlorobenzenes with two molecules of 2-propanol [57] calculated in [51, 60, 66, 67] with hydrogenation rates in this solvent, a tendency to increase the effective reaction rate with an increase in the negative charge at nitro groups was also found. A different form of the dependence of the hydrogenation rate on the nitro group of nitroarenes for different catalysts, for example, for Pd/C and the same catalyst with the addition of a cerium complex with nitrilotrimethylphosphonate [57], is explained in [51, 60] by the change in the nature of the active sites upon contact of the complex compound. This changes the nature of the adsorption of nitro compounds and hydrogen, which leads to the opposite effect of the charge of the nitro group on the rate of hydrogenation. Existence of the linear relation between efficient charges on the reactionary centers of the substrates qreactive centers is revealed. c., corresponding to the hydrogenation direction of reaction – NB, NSBNitrosobenzene, PHA – Phenylhydroxylamine, and AN, both s-values and sI-constants of their functional groups [54] that indicates adequacy of the applied computational method. The rates and mechanisms of reactions are largely determined by the structure of the reagents. Studies of the structure of nitroarenes have been carried out in a number of works using experimental methods such as vibrational spectroscopy, gas electron diffraction (GED), X-ray diffraction analysis (XRA), microwave spectroscopy (MVS), Raman and Infrared spectroscopy, and quantum chemical calculations [68 – 72]. The structure of the NB molecule is the most investigated. According to the GED data and ab initio calculation [68], the NB molecule is flat, which agrees with the existing ideas about the 48

conjugation of the nitro group with the benzene ring; the molecules of the majority of substituted nitroarenes are also planar, and only when the substituent is introduced into the 2-position, the conjugation is broken and the nitro group rotates around the C-N bond [69]. The flat conformation of the NB molecule is energetically more advantageous and provides a more effective acceptance of the electron density from the 2- and 4-positions of the benzene ring as compared to the orthogonal conformation. The barrier of rotation of the nitro group is 12-17 kJ·mole-1 according to the experimental data in [68, 69] and 2125 kJ·mole-1 – according to calculations in [69, 73], which indicates the impossibility of its free rotation. In [13,74] a number of radical anions formed at mono-reduction of 1-substituted-2,4-dinitrobenzenes was calculated. It was found that the orientation of the mono-reduction of polynitrobenzenes is related both to the orbital characteristics of the radical anions and to the ratio of the charges on the oxygen atoms of the nitro groups of the nitro compound and the corresponding radical anion. For a number of nitroarenes, a correlation was found between the initial hydrogenation rates on the Pt/Al2O3 catalyst and the NBMOs energies [75]. It has been calculated by calculation that in the hydrogenation of nitrochlorobenzenes on skeletal nickel, orbital control takes place, and the rates of dehalogenation of the aminochlorobenzenes formed during the reaction are related both to their MO energies and to charges at C-Cl bond atoms [76]. It was established in [77] that when hydrogenating on palladium catalysts, the effective activation energy depends linearly on the energy of NBMOs of nitroarenes, and the reaction rate decreases with increasing negative charge on the nitro group, whereas on the nickelchromium contact an inverse charge dependence is observed. At the same time, it was found in [65] that the rate of hydrogenation of NB and isomeric nitrochlorobenzenes on palladium catalysts increases with increasing negative charge on the nitro group q (NO2). For 10 ortho-substitutes of NB, the correlation dependences lg k = f [q (NO2)] and lg k = f [q (NO2),b], close to linear, were obtained, where k is the rate constant of hydrogenation, and b is the volume of the substituent. Quantum-chemical methods are widely used in the analysis of the reactivity of nitroarenes in reduction [28, 44-46, 78-80]. In particular, for mono- and dinitrobenzenes, the relationship between electronic 49

and structural parameters has been revealed with the features of their vibrational spectra [80]. A correlation was found between the ratio of the yields of ortho- and para-isomers formed during mono-reduction of substituted dinitrobenzenes and the ratio of the contributions of the oxygen atoms of ortho and para-nitro groups to the HOAO (Highest Occupied Atomic Orbital) anion radicals. The solvent can significantly affect the rate of hydrogenation, changing the content of different forms of hydrogen in the surface layer of the catalyst. Adsorption of hydrogen and solvent has a competitive nature [81]. Under the action of the solvent, equilibrium is shifted in the adsorption of molecular and atomic forms of hydrogen and their concentrations on the surface of metals change. In aprotic solvents, the specific solvation of the catalyst surface has a significant influence on the equilibrium. In proton-donor environments, the basic role is played by the acid-base properties of the solvent. Under the action of H+ and OH- ions, a heterolytic decomposition of the molecular forms of hydrogen can occur, which is energetically more advantageous in polar solvents. In the presence of a strong base in the system, the H2 molecule splits into a proton and a hydride ion even in the absence of a metal [82]. The solvent, by changing the distribution coefficient of the substrate between the surface and the solution, reduces its adsorption [8]. For example, in the hydrogenation of 4-nitrotoluene on skeletal nickel [83, 84], an increase in the concentration of 2-propanol in its mixtures with water leads to a change in the limiting stage from the adsorption of hydrogen to chemical interaction, which is associated with the effect of nitrogene solvation on its adsorption. To study the effect of the solvent on the reactivity of nitro compounds [13, 45, 46, 85], along with the experimental ones, the methods of quantum chemistry are applied. The modeling of the hydration of molecules and anion radicals of substituted dinitrobenzenes [13, 45] showed that solvation has little effect on their geometric characteristics as compared to the gas phase, but affects the electronic properties. The non-specific solvation of both the neutral molecule and the radical anion is not accompanied by a significant charge redistribution. At the same time, the specific interaction of the 2,4dinitrochlorobenzene radical anion with a water molecule leads to an increase in the negative charge on the nitro group. The important role 50

of nonspecific solvation of reagents and intermediates in the mechanism of reduction of nitroarenes with titanium chloride is indicated by the differences between the characteristics of NB molecules, the products of its incomplete reduction and their radical anions, calculated for the gas phase and taking into account the effects of the aqueous-alcohol solvate environment [46]. An analysis of the reaction mechanism on the basis of experimental data and modeling results showed that the limiting stage of reduction in aqueous alcohols is the interaction of the solvated substrate and the reducing agent, leading to the formation of a radical anion [46]. The modeling results indicate that the use of alcohol as a solvent should, on the one hand, facilitate the adsorption of nitroarene and its hydrogenation intermediates on the catalyst, as well as the desorption of the target product, and on the other hand, facilitate the reaction by increasing the absolute values of charges on nitrogen atoms substrates. The obtained dependences in [51] indicate that the q (N) values can serve as descriptors for the reactivity of nitrobenzene and products of its incomplete hydrogenation both in the gas phase and in the solvent. In [86-89] the mechanism of hydrogenation of 4,4’dinitrostilbene-2,2’-disulfonic acid (DNS) on Pd-Cu/sibunite by quantum-chemical calculations using the nonempirical HF method in the 6-31G** basis and the semiempirical AM1 method was studied. The most stable conformation of DNS which provides selective hydrogenation of nitro groups is revealed. It is known that 4,4'-diaminostilbene-2,2'-disulfonic acid (DAS) is synthesized by hydrogenation of 4,4'-dinitrostilbene-2,2'-disulfonic acid (trans-DNS), which is used to produce phosphorescent whiteners for fibers and paper. In the industry, the DNS is reduced by iron shavings in an acidic environment unselectively along parallelsequential routes according to the scheme (fig. 15). DNS is the complex organic compound containing except 2 benzene rings, C=C bonds and different functional groups (two NO2-and two HSO3groups). In DNS both two nitrogroups with formation of DAS, and a stilbene olefinic bond to dinitrodibenzyldisulphonic acid (DNDB) and diaminodibenzyldisulphonic acid (DADB) can be hydrogenated. In addition to hydrogenation, the processes of hydrogenolysis of HSO3groups and the destruction of C-C and C-C stilbene bonds into simpler 51

molecules can occur. It is very important to carry out the process selectively on nitro groups, because the hydrogenation product of the double bond and the hydrogenolysis products significantly reduce the bleaching properties of the DAS. For this purpose catalyst PdCu/sibunite was developed [90], on which only nitro groups with the yield of DAS up to 93% are selectively hydrogenated. To establish the mechanism of the process, information is required on the geometric structure of the DNS molecule and its adsorption on the catalyst surface. The geometric structure of stilbenes is determined by two competing effects: conjugation in the p-system and steric interactions. According to the literature data in cis-stilbene due to steric interaction, the angle of rotation of the rings is 30-40°[91]. According to X-ray structural analysis in the crystalline state, trans-stilbene has a practically flat structure. However, for free trans-stilbene molecules, there are conflicting experimental data in the literature. A study of the conformational composition of DNS in [86-89] was carried out within the framework of the semiempirical AM1 method using the standard conformational search procedure (HYPERCHEM6 software package). In this case, the dihedral angles d1 and d2 in the stilbene with two volumetric electronegative substituents without their internal rotation varied (fig. 16), as well as the angles of rotation of the sulfo groups relative to the plane of the rings. The authors constructed a diagram of the potential surface in the coordinates d1-d2 (fig. 17), which shows 16 local minima, which can lead to disagreements in the interpretation of the experimental data. The energy values of the transition between the minima of the potential energy were estimated in the procedure for the search for the transition state. The total number of DNS conformers can be estimated based on the results obtained for o,o-dichlorostilbene and osulfoxystyrene. Each of the 16 conformers, characterized by different combinations of angles of rotation of benzene rings relative to the plane of the ethylene bond, can have nine different combinations of rotation angles in the two sulfoxyl groups (3·3), in total 144 DNS conformers are possible. However, in the DNS, a pair of hydrogen bonds, characteristic of acids, appears in the most stable conformation. An estimate of the energy of the hydrogen bond between the sulfoxy groups carried out for the CH3-SO3H dimer gave a value of about 52.8 kJ/mol (for 52

comparison, the experimental value of the heat of dimerization of formic acid is 59.0 kJ/mol).

Figure 15 – Scheme of DNS hydrogenation

Figure 16 – Scheme of the DNS molecule with dihedral angles of rotation

This effect considerably exceeds the conformational effects in stilbenes. The formation of the ring hydrogen bond leads to the fact that the sulfo groups are located on one side of the benzene rings. For the most stable conformation, the authors made a quantum-chemical calculation by the nonempirical HF method in the 6-31G ** basis with complete optimization of the geometry. In the obtained structure (fig.17, 18), the planes of benzene rings are unfolded relative to the plane of the ethylene group at angles close to 60°, which is confirmed by the results obtained by the semiempirical method AM1. Instead of the labile behavior characteristic of stilbenes, a molecule of DNS with two sulfo groups in the ortho-positions of benzene rings acquires 53

considerable rigidity. This form of the DNS molecule with unfolded benzene rings and a shielded stilbene bond complicates its planar adsorption. As a result, the molecule can only be adsorbed by one or the other nitro group. IR spectra of the individual and adsorbed DNS on the surface of the catalyst (tab. 6) show that the adsorption of the DNS molecule occurs via nitro groups (absorption band 1,520-1,360 cm-1). The frequency of symmetric and asymmetric stretching vibrations of NO2 groups during adsorption is shifted to a low-frequency region by a negligible amount. In this case, the absorption band of the benzene ring (1,640-1,580 cm-1) remains unchanged, but there is a redistribution of the intensity of C = C-vibrations, which is also related to the adsorption of the nitro group.

Figure 17 – The chart of a surface of a potential energy of DNS constructed in coordinates z1 and z2 – two dihedral corners of a turn of benzene rings concerning the plane of an olefinic bond.

The IR spectra of the catalyst after the reduction of the DNS indicate the presence of bands of valence (3,400 cm-1) and deformation (1,620 cm-1) vibrations of NH2 groups. The bands in the region of 54

1,360 cm-1, referring to the vibrations of the nitro group, practically disappear, i.e. nitro group has completely turned into an amino group (DAS). Taking into account the geometry of the DNS molecule, the nitro groups are not adsorbed simultaneously, as a result of which they are hydrogenated sequentially. This is confirmed by the results of the analysis: nitroamino intermediate products are found in the catalyst during the course of the reaction. In the DNS and DAS spectra in the 1,640-1,620 cm-1 region, an intense absorption band is observed, due to oscillations of the stylbene bond C = C, i.e. this stilbene bond is not hydrogenated.

Figure 18 – The molecule DNS geometry optimized by the HF/6-31G method in two projections

Table 6 – IR spectra of groups and bonds of DNS and DAS (n, cm-1) Compound

-СН=СН-

DNS

1,620 1,640

С=С (aromat.) 1,620 1,640

DAS

1,620 1,640

1,580 1,620

DNS/catalyst

1,640

1,640

С-Н (aromat.) 950 1,050 1,150 970 1,040 1,130 1,030 1,080

55

NО2

NH2

1,360 1,520

-

-

1,620 3,400

1,350 1,520

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66. Сергеева Т. А., Ибрашева Р. Х., Фасман А. Б., Васильев Ю. Б. О механизме электровосстановления нитробензола на платине // Электрохимия. – 1978. – Т. 14, вып. 6. – С. 963-967. 67. Van der Avoird A. Some model calculations for adsorption on transition metals // Surface Sci. – 1969. – V. 18, № 1. – P. 159-177. 68. Травень В. Ф. Электронная структура и свойства органических молекул. – М.: Химия, 1989. – 384 с. 69. Domenicano A., Schultz G., Hargittai I., Colapietro M., Portalone G., George P., Bock C. W. Molecular structure of nitrobenzene in the planar and orthogonal conformations. A concerted study by electron diffraction, X – ray crystallography and molecular orbital calculations // Struct. Chem. – 1990. – V. 1, № 1. – Р. 107-122. 70. Politzer P., Abrahmsen L., Sjoberg P. Effects of amino and nitro substituents upon the electrostatic potential of an aromatic ring // J. Am. Chem. Soc. – 1984. – V. 106, No4. – P. 855-860. 71. Davis L. P., Guidry R. M. MINDO/3 study of nitrobenzene // Aust. J. Chem. – 1979. – V. 32, № 6. – Р. 1369-1374. 72. Arnautova E. A., Pivina T. S., Gladkikh O. P., Vilkov L. V. Comparative analysis of intramolecular parameters of nitrocompounds: crystalline and gas phases // J.Mol. Struct.: Theochem. – 1996. – V. 374, № 1-3. – P. 137-145. 73. Бардина А. В. Конформационные свойства молекул замещенных бензолсульфонамидов и бензолсульфонилгалогенидов по данным методов газовой электронографии и квантовой химии: дис. … канд. хим. наук.-Россия, Иваново, 2009. – 165 с. 74. Бегунов Р. С., Орлов В. Ю., Котов А. Д., Копейкин В. В., Лейбзон В. Н., Миронов Г. С. Ориентация моновосстановления в несимметричных однозамещенных динитробензолах // Изв. вузов. Химия и хим. технология. – 1998. – Т. 41, вып. 4. – С. 61-64. 75. Воронин М. В. Синтез нафтиламинов каталитическим гидрированием и гидрогенизационным аминированием: дис. … канд. хим. наук, Россия, Иваново, 1999. – 114 с. 76. Лефедова О. В., Гостикин В. П., Гиричева Н. И. Индексы реакционной способности и скорость дегалоидирования нитро- и аминохлорбензолов в условиях жидкофазной каталитической гидрогенизации // Изв. вузов. Химия и хим. технология. – 1990. – Т. 33, вып. 12. – С. 94-98. 77. Терешко Л. В. Синтез ароматических и жирноароматических аминов на палладийсодержащих катализаторах: дис. ... канд. хим. наук.- Россия, Иваново, 1990. – 163 с. 78. Barone G., Duca D. Ab initio study of structure and energetics of species involved in the 2,4-dinitrotoluene hydrogenation on Pd catalysts // J. Mol. Structure: Theochem. – 2002. – V. 584, № 1-3. – P. 211-220. 79. Kacer P., Cerveny L. Structure effects in hydrogenation reactions on noble metal catalysts // Appl. Catal. A: General. – 2002. – V. 229, № 1-2. – P. 193-216. 80. Крылова Н. Ю. Региоселективность моновосстановления и свойства динитроаренов: дис. … канд. хим. наук. – Россия, Ярославль, 2009. – 116 с.

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81. Улитин М. В., Барбов А. В., Лефедова О. В., Гостикин В. П. Реакции жидкофазной каталитической гидрогенизации в тонком органическом синтезе // Изв. вузов. Химия и хим. технология. – 2005. – Т. 48, вып. 7. – С. 62-72. 82. Сокольский Д. В., Дорфман Я.А. Координация и гидрирование на металлах.- Алма-Ата: Наука Каз. ССР, 1975. – 216 с. 83. Захаров О. В., Улитин М. В., Комаров А. А. Кинетика гидрогенизации 4-нитротолуола на скелетном никеле в водных растворах 2-пропанола. I. Экспериментальное определение кинетических параметров реакции // Изв. вузов. Химия и хим. технология.-2010. – Т. 53, вып. 7. – С. 85-89. 84. Захаров О. В. Кинетика жидкофазной гидрогенизации 4-нитротолуола в бинарных растворителях 2-пропанол-вода: дис. … канд. хим. наук.- Россия, Иваново, 2011. – 147 с. 85. Вокин А. И., Шулунова А.М., Лопырев В. А., Комарова Т. Н., Турчанинов В. К. Сольватохромия гетероароматических соединений. I. Особенности взаимодействия 4-нитропиразола с амфипротонными растворителями // Журн. орг. химии.- 1998. – Т. 34, № 11. – С. 1741-1747. 86. Сасыкова Л.Р., Масенова А.Т., Досумова Б.Т., Касенова Д.Ш., Бижанов Ф.Б. Синтез аминов из ароматических нитросоединений : разработка оптимальных условий и эффективных катализаторов // Межд. симпозиум, посв.100- летию со дня рождения К.И.Сатпаева, Материалы конференции, Том 2, Алматы, КазНТУ, 1999, 573-576. 87. Масенова А.Т. Исследование механизма гидрирования 4,4’-динитростильбен-2,2’-дисульфокислоты на Pd-Cu катализаторах, Изв. НАН РК, сер.хим, №.1, 2008, 8-10. 88. Masenova A.T., Sasykova L.R., Dosumova B.T., Bizhanov F.B. Catalytic synthesis of amines of aromatic and aliphatic rows // 4-й Межд. симпозиум по гетерогенному катализу и тонкой химии. Материалы конференции, Book of Abstracts, Final Programm, Базель, Швейцария, 1996, p.166-167. 89. Масенова А.Т. Гидрирование ароматических нитросоединений и углеводородов на гетерогенных катализаторах на основе металлов VIII группы… дисс. на соискание ученой степени д.х.н., Казахстан, Алматы, 2010, 267с. 90. Масенова А.Т., Досумова Б.Т., Бижанов Ф.Б. А.С. №1818810 CCCP. Способ получения 4,4’-диаминостильбен-2,2’-дисульфокислоты // Опубл. 11.10.92. 91. Верещагин А.Н. Конформационный анализ углеводородов и их производных. М: Наука, 1990. 296 с.

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Part III. MECHANISM OF CATALYTIC REDUCTION   OF AROMATIC NITRO COMPOUNDS    Chapter 5. Ideas of D.V. Sokolsky. Four mechanisms of the liquid-phase hydrogenation offered by D.V. Sokolsky This part is started from describing works of D.V. Sokolsky, devoted to hydrogenation in liquid phase. Dmitry Vladimirovich Sokolsky (1910-1987) is the founder of school of sciences of a catalysis in Kazakhstan. D.V. Sokolsky is one of the very important organizer of a science, the Hero of Socialist Work. D.V. Sokolsky scientific interests have been directed on working out of the theory and practice of many areas of catalysis. D.V. Sokolsky had made a big contribution to works on catalytic purification of gases which had been for the first time begun in the former Union. The school of sciences in field of catalysis created by D.V. Sokolsky successfully continues researches in the field of development of new catalytic and electrochemical technologies for processes of petrochemical, inorganic and organic synthesis, oil refining and gas. Academician D.V. Sokolsky made an invaluable contribution to the formation of the chemical faculty of the al-Farabi KazNU, he was the founder of the department of catalysis and petrochemistry (in 19451970 – the department of catalysis and technical chemistry). He worked as an assistant professor, head of the department, pro-rector of KazNU (former S.M. Kirov KazSU). He was a Deputy Director of the Institute of Chemical Sciences, the Scientific Secretary of the Presidium of the Academy of Sciences of the Kazakh SSR and Vicepresident of the Academy of Sciences of the Kazakh SSR. In 19691987 years he was a Director of the Institute of Organic Catalysis and Electrochemistry in Almaty, Kazakhstan (from 2015 the JSC “D.V. Sokolsky Institute of Fuel, Catalysis and Electrochemistry”) of the Academy of Sciences of the Kazakh SSR, which was founded on December 1, 1969. One of the main directions of the catalytic school of D.V. Sokolsky is devoted to catalytic hydrogenation in solutions. 62

The liquid-phase hydrogenation is carried out by hydrogen barbotage through liquid reactionary mass. The method of liquid hydrogenationis now one of the most developed methods in the theoretical and practical relation. The liquid-phase reactions differ from gas-phase a number of factors, in particular: – a thermodynamic condition of system, – presence of a salvation layer on a catalyst surface, – possibility of direct electrochemical mechanisms. Solvent can influence both for the rate, and the reaction mechanism. Rate of diffusion depends on viscosity of solvent. Rates of the chemical reactions can sufficiently change depending on the solvent nature. A high degree of chemo-, regio-, stereoselectivity of catalysts in the reactions of hydrogenation is very important. Use of catalysts on the basis of Ni or Co with Мо or W gives to their mixtures and alloys the bifunctional properties – ability to carry out simultaneously both homolytic, and heterolytic reactions and stability in relation to poisoning action of the sulphurous and nitrogenous compounds containing in oil raw materials. Application of carriers allows to lower the content of the active components in catalysts that is especially important in case of use of expensive metals. D.V. Sokolsky created the theory of optimization of hydrogenation catalysts. He developed a potentiometric method for studying working catalysts-electrodes [1]. The choice of the optimum catalysis in the case of catalytic hydrogenation can be solved with its preliminary electrochemical characteristics. The removal of the potentiostatic curves and the measurement of the potential during the reaction give so much information about the limiting stages and the reaction mechanism that, after the first experiment, far-reaching conclusions can be drawn about ways to improve the catalyst. Basically, there are three types of processes that occur when the surface of the catalyst is significantly filled with hydrogen, when the surface is filled with an unsaturated compound, and finally processes whose first stage is the transfer of an electron by the surface to an unsaturated compound. In this case, an anion-radical is formed, which can be converted into a solution. Changing the conditions of the process, you can move from one 63

mechanism to another. The measurement of the potential of the catalyst immediately gives an answer to the question of the type of reaction [2]. Thanks to the application of electrochemical methods, developed by the catalytic school D.V. Sokolsky, it became possible to determine the concentrations of reactants on the surface of catalysts during the reaction, the ratio of various forms of hydrogen in the catalyst, the average binding energy of hydrogen to the surface, the presence of charged forms of organic compounds and the surface area of the catalyst itself. Of particular importance in the practice of catalytic hydrogenation has been the application of these methods to powder catalysts. In a number of cases, measuring the potential of the catalyst during the hydrogenation of various compounds, including nitro compounds, it is possible to determine the selectivity of the process and the adsorption of reaction products on the surface. Researchers managed to transfer electrochemical methods of investigating the mechanism of reactions to processes in dielectric media and even in the gas phase. Ionic and radical reactions proceed in solutions on the surface of the catalyst, with adsorbed hydrogen being most often positively charged, and unsaturated compounds acquiring a positive or negative charge. D.V. Sokolsky showed that electrochemical methods of investigation make it possible to determine the mechanism of action of additives on the activity of the catalyst. In the selection of hydrogenation catalysts in the liquid phase, it is also possible, with the aid of the composition of the solution, to regulate the binding energy of hydrogen to the surface and, consequently, the speed and selectivity of the process [3]. The rate and mechanism of catalytic hydrogenation reactions in solutions depend on the chemical nature of the catalyst, the composition of the solution, and the structure of the unsaturated compound. The use of electrochemical methods for the study of catalysts (measurement of the potential and electrical conductivity of powdered catalysts) makes it possible in each case to determine the amount of hydrogen absorbed by the catalyst, the average binding energy of the catalyst with the surface, the rate of renewal of hydrogen, the ratio of the concentrations of the reactants on the surface during the reaction, and the limiting stage of the process. Knowing these 64

characteristics, along with kinetic data, it is easier to select the optimal catalysts for hydrogenation of various classes of unsaturated compounds. D.V. Sokolsky showed that when elimination of diffusion limitations, the rate and mechanism of catalytic hydrogenation in solutions are determined by the chemical nature of the catalyst, the composition of the solution, and the structure of the unsaturated compound. The use of electrochemical methods for the study of catalysts makes it possible in each case to establish the mechanism of the influence of various factors on the course of the reaction. Promotion of nickel catalysts to varying degrees affects the rate of hydrogenation of acetylene and ethylene derivatives. Alloys of nickel with additives have a high catalytic activity in hydrogenation. The maxima of the catalytic activity fall on alloys of different composition, depending on the nature of the hydrogen bond and the magnitude of the displacement of the potential during hydrogenation. The presence of other cations in nickel catalysts leads to the modification of the catalysts and allows for hydrogenation to be strictly selective. The measurement of the conductivity of catalyst powders in solution gives a new method for determining the various forms of hydrogen sorbed by the catalyst. Optimal catalysts for the hydrogenation of certain compounds can be selected taking these factors into account [4]. 4 mechanisms of reaction of hydrogenation of D.V. Sokolsky [1, 5] Wide expansion of works on catalytic hydrogenation in the Soviet Union in many respects was promoted by D.V. Sokolsky monography “Hydrogenation in solutions” become by the reference book of the researchers working in area of hydrogenation. The book has summed up to scientific achievements in area of the liquid-phase hydrogenation. In detail, the monograph deals with the theory of the prediction of catalytic actions. The basic researches of the Kazakhstan school of chemists in area of catalysis have allowed to solve a number of practically important problems of the chemical industry. One of examples of successful introduction of scientific workings out is modernization of the industry of hydrogenation of fats.

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He worked out conception about 4 mechanisms of catalytic hydrogenation in solvents: The 1-st mechanism It is realized in that case when the catalyst surface is covered by hydrogen, the catalyst potential practically is not displaced in anode area and rate of hydrogenation is directly proportional to concentration of unsaturated compound in a solution. It occurs for the compounds, which heat of adsorption below heat of adsorption of solvent on the used catalyst. A limiting stage is activation of unsaturated compound. Reaction is better proceeds in acid solutions, than in the alkaline. The most suitable catalysts: Rh, Rh-Pd. The 2-nd mechanism It is characteristic for process with participation of unsaturated compound with the raised adsorbtive ability when rate speed of reaction in the essential degree depends on energy of bond of atomic hydrogen with a surface. Optimum catalysts are: Pt-Ru, Pd-Ru, Ni-Pt, Ni-Pd. The 3-rd mechanism It is realized in that case when unsaturated compound displaces from a surface hydrogen and solvent molecules. Reaction is limited by hydrogen activation. Rate of reaction does not depend on concentration of unsaturated compound in a solution. Such reactions proceed at the expense of the dissolved hydrogen. Typical catalysts: Pd, Pt. The 4-th mechanism Essentially differs from other 3 mechanisms. The limiting stage is connected with transfer of electron, and the temperature effect of reaction is close to zero. A reaction order on unsaturated compound, basically, is equal to zero. Catalysts: Pt, Pt-Pd, Ir, Rh, Ni-Cr, Ni-Mo.

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Chapter 6. Different variants of the mechanisms of hydrogenation of nitrobenzenes and intermediate products of reduction of the nitro group It is known that the regularities of the reactions of hydrogenation of substituted nitrobenzenes are directly related to the staging of the nitro group transformations. The complex study of individual stages of the reaction makes it possible to reveal the most probable mechanism of interactions, to determine the reactivity parameters of the initial and intermediate compounds, to form the basis for the mathematical description of the process under study. An important component of this approach is the systematic study of the kinetics of the individual stages of the transformation of the starting materials and reaction intermediates. In the literature, various variants of conversion schemes for substituted nitrobenzenes are given. Haber [6] in 1898-1900 for the first time proposed a general scheme for the formation of possible substances in the electrochemical reduction of nitrobenzene in the presence of strong bases or strong acids and in an almost neutral medium (in very weakly alkaline or slightly acidic). Debus and Jungers proposed a scheme for the catalytic reduction of nitrobenzene on Raney nickel (fig.19) [7]. They suggested the formation of azobenzene through the interaction of nitrobenzene and amine. Another scheme for the reduction of nitrobenzene, which is a continuation of the schemes of Debus, Jungers and Haber, was created in [8]. V.P. Shmonina [9, 10], in order to determine the mechanism of catalytic reduction of nitro compounds, the reduction of nitrobenzene and twenty derivatives of it on skeleton nickel, Pt- and Pd-blacks studied with a wide variation of the process: catalyst charge, solvents, concentration of nitrocompounds, temperature, stirring intensity. The effect of various additives in the reaction mixture (nitrobenzeneaniline intermediates, acid, alkali, pyridine, aniline, etc.) was studied. In the work such control methods of the course of catalytic process as definition of saturating speed of hydrogen, measurement of potential of the catalyst by V. Drouz and D.V. Sokolsky [9] method, use of a polarography [10], a conductometric titration were applied. 67

It was found that the actual hydrogenation processes can be accompanied by the interaction and isomerization of the intermediate compounds. The ratio of hydrogenation rates and reactions of interaction of intermediate products affect the nature of intermediate stages and intermediate products, selectivity and depth of reduction. Scheme of transformations of aromatic nitrocompounds, proposed by V.P. Shmonina (fig. 20), largely coincides with the schemes of F. Gaber and V.O. Lukashevich [11], which were proposed for electrochemical and chemical methods for the aromatic nitrocompounds reduction, but it has its own peculiarities. In the schemes proposed before the studies by V.P. Shmonina, there was no reaction of direct conversion of phenylhydroxylamine (PHA) to hydrazobenzene (HB), or isomerization of azoxybenzene (AOB) to oxyazobenzene. The reaction of the formation of azoxybenzene from nitrobenzene and phenylhydroxylamine under the conditions of the experiment, as in the scheme of V. Lukashevich, was also not noticed. Nor was the formation of azobenzene through the interaction of nitrobenzene with aniline and the formation of p-aminophenol from hydroxylamine indicated in the Debuss and Jungers scheme. Three directions of course of process of reduction were found by Shmonina V. P. in the studied conditions. It follows from the scheme in fig. 20 that the substituted nitrobenzenes (1) are converted to the corresponding amines (4) as a result of successive catalytic interaction of the nitro group with three moles of hydrogen through the formation of intermediate nitrosobenzenes (2) and arylhydroxylamines (3). This first direction is purely hydrogenation direction, it is a sequential interaction of a nitro group with three hydrogen molecules. Intermediates may be nitrosobenzene and phenylhydroxylamine, but they do not accumulate in the reaction mixture and are reduced to aniline as they form. Under certain conditions, for example, causing a decrease in surface concentrations of adsorbed hydrogen, homogeneous condensation of the intermediate reaction products becomes possible. Leading to the formation of substituted azoxy (6) or azobenzenes (7), which catalytically interact with hydrogen through intermediate hydrazobenzene (8), are converted to the corresponding amines.

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The second direction is the interaction of nitrobenzene with phenylhydroxylamine, leading to azoxybenzene, which is further converted to aniline through azo and hydrazobenzene. The third direction is distinguished by the fact that the phenylhydroxylamine formed as a result of the reduction of nitrobenzene is subsequently converted to hydrazobenzene. On catalytically active centers with low reactivity, the disproportionation of substituted arylhydroxylamines (9) into aminobenzenes and nitrosophenols is possible [12, 13], which, reacting with hydrogen, can be converted to aminophenols (9). The intermediate azoxy (6) and hydrazobenzenes (8) under certain processing conditions can be homogeneously rearranged to 4hydroxyazobenzene (10) and benzidine (11), respectively. At elevated hydrogen pressures, the possibility of further hydrogenation of aniline (4) in cyclohexylamine (5) is not ruled out. The transformation of the nitro group of substituted nitrobenzenes in the hydrogenation direction is carried out by reacting on platinum and palladium in water-organic and alkaline media, as well as on skeleton nickel in organic solvents, for example, in aqueous solutions of aliphatic alcohols [12, 14, 15]. An increase in the contribution of the hydrogenation direction to the overall hydrogenation rate is facilitated by a decrease in the concentration of the hydrogenated compound and an increase in the hydrogen pressure. The most rapid condensation of intermediate products leading to the formation of substituted azoxy- and azobenzenes occurs during the reaction on platinum black and skeletal nickel in solutions containing electron-donor additives or in strongly alkaline media at high initial concentrations of the hydrogenated compound [11-16]. It should be noted that nitrosobenzene in reaction systems most often is not fixed as the intermediate product, but is introduced into nitrobenzene conversion schemes as a product preceding the formation of phenylhydroxylamine [19-27]. Most likely, the argument for including nitrosobenzene in the scheme for the conversion of nitrobenzene is the sequence of stages described in earlier works [18, 19, 28], since there is no direct evidence of the presence of nitrosobenzene in the solution volume by the authors [21, 24, 25, 27].

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In a number of papers [29, 30], the data confirming the formation of nitrosobenzene as an intermediate product are given.

Figure 19 – Nitrobenzene reduction scheme [7]

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Figure 20 – The main products and stages of conversion of nitrobenzene and its substituted: 1 – nitrobenzene; 2 – nitrosobenzene; 3 – phenylhydroxylamine; 4 – aniline; 5 – cyclohexylamine; 6 – azoxybenzene; 7 – azobenzene; 8 – hydrazobenzene; 9 – 4-aminophenol; 10 – 4-hydroxyazobenzene; 11 – benzidine [12-15, 17-19].

An analysis of the results presented in the works [31-34], allows us to state that in order to explain the kinetic regularities of the hydrogenation reactions of substituted nitrobenzenes, in most cases, the authors refer to the same type of chemical transformation schemes for the nitro group. M. Geirovsky [30], in the polarographic reduction of nitrobenzene in aqueous, aqueous-alcoholic and acidic media, found that nitrobenzene joins 4 electrons and is reduced to phenylhydroxylamine, which, further, attaching two electrons at more negative potentials, turns into aniline through azoxybenzene. In an alkaline medium, nitrobenzene attaches 6 electrons at once and, without leaving the cathode, turns into aniline. In an alkaline medium, nitrobenzene attaches 6 electrons at once and, without leaving the cathode, turns into aniline. The reduction of aromatic nitrocompounds on a supported 3% Pt/SiO2-AlPO4 catalyst was studied in [36, 37]. The authors propose the following mechanism for the hydrogenation of aliphatic and aromatic nitro compounds on supported Pt catalysts (11):

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1 ArNO2 ‫׀‬ ArNO2 + metal → oxidized metal surface + ArN:(адс.) → R-N-O2 H2 (dimeric or oligomeric intermediates) → R-NH2 + металл + H2

(11)

In this case, the presence of electron-donating groups should slow down the first stage, and, consequently, inhibit the formation of nitrene, thus giving an increase in the lower conversion than nitrobenzene. Conversely, the presence of electron-accepting substituents should stabilize the intermediate nitrene and the rate to stage (2) with respect to nitrobenzene. In studies [38-42], upon reduction of chloronitrobenzene to Niskeleton, 5% Ir / C, the main intermediate of the reaction was chlorophenylhydroxylamine. The adsorptive capacity of the starting compound is higher than that of chlorophenylhydroxylamine, so the authors suggested that, while there is chloronitrobenzene on the surface of the catalyst, phenylhydroxylamine accumulates in the reaction mixture without further conversion to chloroaniline. The authors found that chloraniline forms in the entire range of the investigated concentrations of chloronitrobenzene in the reaction mixture. Based on the analysis of reaction products and hydrogen balance from the gas phase, it was assumed that, together with the hydrogenation direction of reaction (12): H2 H2 H2 ArNO2 → ArNO → ArNHOH → ArNH2

(12)

there is a disproportionation of phenylhydroxylamine on the nitrosoand amino compound according to reaction (13): 2 ArNHOH ↔ ArNO + ArNO2 + H2

(13)

The nature of the catalyst, the temperature of the test, the pH of the medium have a significant effect on the disproportionation rate of phenylhydroxylamine. Catalysts on the activity in this reaction form a series: Ni o-OH > m-CHO > o-NH2 > p-OC2H5 > m-OH > m-CH3> H > m-NH2 > p-CH3 > p-OH. The p- and m-substituents in this series, with the exception of pOC2H5, are located in the series shown according to the values of the Hammett substituent constants in decreasing order. In [110], when the nitrobenzene, o-nitroanisole, o-nitrophenol, dinitrotoluene, and p-nitrophenol were reduced at atmospheric pressure, it was found that the apparent activation energies are very different and are in the range 20.1-36.0 kJ/mol. The highest adsorption capacity was observed for o-nitrophenol. The authors believe that a rather large spread in the values of apparent activation energies is associated with the structure of nitro compounds and the influence of substituents on the electron density in the aromatic nucleus. The reduction of nitroalkylphenols at room temperature and atmospheric pressure was studied in [111]. It is shown that the reduction rate decreases with increasing size and complication of the structure of the substituents, which is explained by the authors of the presence of spatial difficulties. In studies [112, 113], in the study of the hydrogenation of nitrobenzene, p-nitrophenol, p-nitrotoluene, pnitrochlorobenzene, p-nitroaniline in various solvents on colloidal Rh and Pd at atmospheric pressure, it is noted that the type of substituent affects the reaction rate in those cases, when the order of the reaction on the substrate is of the first or fractional order. If, on the other hand, the reaction order on the hydrogenated nitro compound is zero, then

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the substituents do not influence the reaction rates and the duration of the process. In [114] the hydrogenation of m- and p-substituted nitrobenzenes in synthesized from colloidal rhodium and palladium catalytic systems supported on polyvinyl alcohol was investigated. The process was studied at atmospheric pressure and ambient temperature. It was found that the reaction order for the nitro compound on both catalysts is zero. The rate of reduction of para-derivatives is reduced in the series: NO2C6H4CN > NO2C6H4CHO > (NO2)2C6H4>NO2C6H4COOH> NO2C6H4I> NO2C6H4Cl> NO2C6H4Br>C6H5NO2> NO2C6H4OCH3> NO2C6H4NH2. For m-substituents authors observed an other series of reducing reaction rate: NO2C6H4Cl> NO2C6H4Br> NO2C6H4CHO > C6H5NO2>NO2C6H4COOH> NO2C6H4NH2. The authors of the study showed an increase in the reduction rate of compounds having substituent groups attracting electrons and, conversely, a decrease in the reaction rate in the case of hydrogenation of nitro compounds with electron-repelling substituents. Halogensubstituted nitro compound with a m-position substituents is reduced on a rhodium catalyst with the highest speed. In the opinion of the authors, the rhodium catalyst is the process due to the presence of ionized hydrogen, and on the palladium catalyst – with the participation of hydrogen atoms. The authors provide a stepwise mechanism for the reduction of nitrobenzene and support their conclusions with data on the electronic configurations of Pd and Rh atoms and the difference in the nature of hydrogen adsorption with palladium and rhodium. In the hydrogenation of various aromatic nitrocompounds in ethanol at atmospheric pressure in the presence of Ru-catalyst reaction rate decreases in the order: p-nitrobenzonitrile > p-nitrobenzoic acid > p-nitrophenol > p-chloronitrobenzene > nitrobenzene, p-nitroanisole, p-nitroaniline, p-nitrotoluene, p-bromonitrobenzene [115]. 84

The reduction of various n- and m-derivatives of nitrobenzene on a colloidal iridium catalyst precipitated on polyvinyl alcohol was studied in [116]. The authors have established that the values of the rates of reduction of p- and m-substituted compounds decrease in the following sequences: m-derivatives: NO2C6H4Cl> NO2C6H4Br> NO2C6H4OCH3> C6H5NO2> NO2C6H4OCH3> NO2C6H4NH2> (NO2)2C6H4 p- derivatives: NO2C6H4CHO > NO2C6H4Cl> NO2C6H4Br> C6H5NO2> NO2C6H4OCH3> NO2C6H4COOH> NO2C6H4CH3> NO2C6H4NH2. The data presented by the authors confirm the conclusions of the authors of the study [114]. The literature and patent data show that the same substituent in the molecule of the aromatic nitro compound has a different effect on the kinetics of the reduction reaction depending on the composition of the catalyst system, the solvent and the process conditions. It is quite obvious that a change in the structure of a molecule due to the appearance of one or another substituent affects the distribution of the electron density in the molecule and the adsorption capacity of the aromatic nitro compound. The reduction of nitrocompounds with carbonyl and carboxyl groups was studied in [117, 118]. The authors noted that the carbonyl and carboxyl groups in the p-position increase the displacement of the catalyst potential, indicating an increase in the adsorption capacity of the aromatic nitro compound. The authors believe that the carbonyl and carboxyl groups are electron acceptors and, by reducing the electron density both in the aromatic nucleus and in the nitro group, cause an increase in the amount of electron density shift from the catalyst to the molecule of the adsorbed aromatic nitro compound. Carbonyl and carboxyl groups not only in the p-position, but also in most cases in the o- and m-positions also cause an increase in the adsorption capacity of the aromatic nitro compound. In contrast to this effect, OH groups, amino, methyl and ethyl groups contribute to a decrease in the adsorption capacity of the aromatic nitro compound [118-120]. These groups are electron donors and their presence in the molecule contributes to a decrease in the 85

electron density in the nitro group, as indicated by a decrease in the displacement of the potential of the catalyst. The adsorption capacity of the hydrogenated nitro compound affects the distribution of the reagents (nitro compound, hydrogen) on the surface of the catalyst, which in turn changes the reaction rate and the mechanism of the process. The adsorption capacity of the hydrogenated aromatic nitro compound and the limiting stage of the process are always related, regardless of the process conditions. By data in [117-119] at reduction on the skeletal nickel catalyst the limiting stage is hydrogen activation therefore at the shortage of hydrogen on a surface the reduction rate considerably decreases. This phenomenon is caused by influence of electrophilic substituents which increase the adsorptive capacity of nitro compound. On the contrary, presence of electron-donating substituents increases reaction rate thanks to the fact that adsorption of nitro compound decreases. The hydrogenation of more than 10 aromatic mono- and dinitrocompounds on Al2O3-supported catalysts based on platinum-group metals in various solvents under increased hydrogen pressure was studied in [96-100, 121-136]. The effect of the structure and position of substituents on the aromatic ring on the kinetics and mechanism of reduction of aromatic nitro compounds over 4% Pd/Al2O3 was studied. It is shown that the aromatic nitro compounds studied are reduced in the hydrogenation direction without accumulation of products of isomerization and hydrogenolysis. Hydrogenated aromatic nitrocompounds, by decreasing the rate of reduction, form a series: p-nitrophenol> o-nitrophenol> p-nitroaniline> m-nitroaniline> onitroaniline>; 2,5-dinitrophenol> 2,4-dinitrophenol> 2,6dinitrophenol (fig. 26). A rectilinear relationship between the rate constants and the constants of Hammett substituents was revealed. The experiments confirmed that electron-donor substituents reduce the rate of reduction of nitro compounds.

86

Figure 26 – Kinetic curves for the reduction of various nitro compounds over 4% Pd/ Al2O3 at PH2 = 1.0 MPa, T = 293 K, A3(6)H2 = 800 cm3, amount of a catalyst, q = 0.1 g: 1 – NB, 2 – 2,5-DNP, 3-p-NP, 4-2,6-DNP, 5-o-NP, 6-p-NA, 7-2,4-DNP, 8-m-NA, 9-o-NA.

Reduction of nitro compounds, as a rule, is carried out at moderate temperatures in the liquid phase (water, water-alcohol mixtures, alcohols, chloroform, etc.). Thus, the hydrogenation of o-, m- and pMNT in isopropanol at 25-60°C and P = 0.1 MPa in the presence of palladium-containing polytrimethylol melamine results in a quantitative yield of the corresponding toluidines: k298 eff (l /mol, Pd/C) are respectively 24 ± 1.19 ± 1.7 ± 1, and the activation energies are 51 ± 5.57 ± 5 and 129 ± 28 kJ / mol. A similar study for m- and pnitrotoluenes was carried out using platinum black as a catalyst [137]. The processes of catalytic reduction of dinitrotoluene (DNT) with hydrogen have been studied in detail in connection with the great practical significance of this stage in the production of toluene diisocyanate (TDI) and, simultaneously, as an example of the reduction of polynitrocompounds. It was shown that during the reduction of 2,4-dinitrotoluene (2,4-DNT) in an alcoholic solution in the presence of platinum or in a water-alcoholic medium in the presence of palladium, the reaction products are 2,4-diaminotoluene (2,4-DAT), 4-hydroxylamino-2-nitrotoluene (4-HA-2-NT), 4-amino2-nitrotoluene (4-ANT). 87

Similar products were obtained from 2,6-dinitrotoluene (2,6DNT). Numerous subsequent studies confirmed the high efficiency of catalytic reduction of DNT with hydrogen to diaminotoluene (DAT) and formed the basis for their modern production. The studies carried out in [30, 138] on the reduction of 2,4-DNT by hydrogen in alcoholic media have shown a great influence of the nature of the catalyst not only on the speed, but also on the direction of the process. On one of the traditional catalysts, Raney nickel, the reduction starts with the nitro group located at position 4 and sequentially passes the 4-amino-2-nitro, 4-amino-2hydroxylaminotoluene and 2-HA-2-NT, 4-diaminotoluene (2,4DAT), nitrosocompounds in the reaction mixtures are not detected; 2amino-4-nitrotoluene was not detected by either GLC or TLC. Before the complete disappearance of DNT, zero order is observed for the nitro compound, which indicates that the hydrogen concentration in the reaction zone is constant and, consequently, the surface of the catalyst, free for absorbing hydrogen, is constant. Due to its high adsorption capacity, DNT displaces the reduction products from the catalyst surface. The introduction of alkali promotes the binding of hydrogen by the catalyst, which is the reason for the increase in the rate of hydrogenation. The activation energy of hydrogenation of DNT at atmospheric pressure is 40 ± 1 kJ / mol (for mononitro compounds 45 ± 2 kJ / mol). In the hydrogenation of DNT on Ni/SiO2 – catalyst [30] initially reduces a nitro group in the 2-position, the process selectivity at 60ºC exceeds 95%. As stable intermediate products, in this case hydroxylamine derivatives also appear. The concentration of 2-HA-4NT in the first period of the process is close to the concentration of the initial nitro compound and considerably exceeds the concentration of 2-amino-4-nitrotoluene, which indicates a high rate of its formation and a much lower expenditure. A similar picture is observed for 4-HA-2-NT on other catalysts. The concentration of 2-HA-4-NT and 4-HA-2NT in the reaction mass depends on the temperature, decreasing as it increases.In a kinetic study of the catalytic reduction of 2,4-DNT on a palladium catalyst [139] (5% Pd on carbon), it was found that the reaction mechanism is close to that described earlier for reduction on Raney nickel.

88

The authors showed that the reaction with the basic substances is the reduction products of the 4-nitro group; in time, the content of 4HA-2-NT and 4-amino-2-nitrotoluene can be monitored. The reaction of reduction of the 2-nitro group in 2,4-DNT proceeds much more slowly. In the kinetic calculations, it is necessary to take into account the formation of 4-HA-2-NT-, 4-amino-2-nitro- and 2-amino-4nitrotoluene (fig. 27, 28). 2-Amino-4-hydroxylaminotoluene was detected in extremely low concentrations. It was suggested that the o-nitro group is converted into an amino group in one step.

Figure 27 – Reduction of 2, 4-dinitrotoluene

Hydrogenation in an alcohol medium is accompanied by the alkylation of the resulting amines, which makes it difficult to further use them. Surprisingly, it was found that the addition of up to 10% (volume) CO to hydrogen sharply slows down these processes [140]. Although the reaction of catalytic reduction of nitro compounds with hydrogen is intended primarily for the production of amines, the derivatives of phenylhydroxylamine, hydrazobenzene, cyclohexylamine may also be the target products [141]. Hydrogenation can be stopped at intermediate stages. The reduction of NB to Pd / C in an alkaline medium leads to the formation of hydrazobenzene in a yield of 93-97% and purity of 99.5 – 99.7% [142]. Hydrogenation of o-MNT in an alcohol medium with a Pd catalyst at 30-150ºC in the presence of bases leads to the formation of 89

hydrazotoluene. Similarly, o-hydrazololuene is obtained in a yield of more than 80% in the presence of sodium hydroxide and quinone. The presence of alkali contributes to the acceleration and selectivity of the reaction, and quinone inhibits further reduction; the dielectric constant of the solvent exerts a strong influence on the process.

Figure 28 – Change in the concentration of reagents upon reduction 2, 4 DNT: 1- 2,4-DNT, 2- 4-hydroxylamino-2-nitrotoluene, 3- 2-amino-4-nitrotoluene, 4-DAT, 5-4-amino-2-nitrotoluene.

When nitro compounds are reduced by hydrogen with Pt/C or Pd/S/Se/C catalysts in the methylmorpholine medium at 28-30ºC, the process stops at the hydroxylamine stage (in the reduction of onitrotoluene, the content of o-tolyl hydroxylamine in the reaction product reaches 96%). As a solvent, methylpiperidine and dimethyl sulfoxide are also used [143]. The influence of the reaction conditions on the direction of reduction is clearly manifested in processes occurring in the main media. The catalytic hydrogenation of 2,4- and 2,6-DNT leads, respectively, to 3,3'-dinitro-4,4'-dimethyl- and 3,3'-dinitro-2,2'90

dimethylazoxybenzenes, the hydrogenation rate in alkaline environment is much higher than in the acid medium. The same products were also obtained by boiling dinitrotoluenes with NaHS in alcohol or benzene. The reduction of NB to cyclohexylamine was observed using Pt, Pd, Ni-Raney catalysts in a 50% ethanol medium at pH 2.4-12.8 [144]. The same product is the main one in the reduction of NB on mixed catalysts containing metallic cobalt [145]. Relatively easy derivatives of cyclohexylamine are obtained by catalyzing the hydrogenation process with Ru-containing catalysts, catalysts based on Rh, Rh-Pt, Rh-Pd, Rh-Ru [96, 97, 126, 130, 134, 146-151]. Nitro-cinnamic acid is reduced to cis-3- (4-aminocyclohexyl) propionic acid in ethanol at 80-100°C, and bis (4-nitrophenyl) ethylene to bis (4-aminocyclohexyl) ethane in dioxane at a temperature above 80°C [152]. It was proposed to reduce 2,4diaminodiphenyl to diaminodicyclohexane over 5% Ru/Al2O3 catalyst [153]. The reduction processes are complicated by side-reactions and secondary reactions that significantly affect the yield of the desired product. 2,4-dinitrotoluene is successfully reduced successively to 3-nitrop-toluidine (in 98% yield) and 2,4-diaminotoluene by hydrogen at room temperature and atmospheric pressure in ethanol and in the presence of a montmorillonite silylamine palladium complex. The catalytic reduction of 2,3- and 3,4-DNT under the same conditions proceeds unusually. At a pressure of 20 MPa and a temperature of 300°C in the presence of Fe2O3, hydrodenitrogenation takes place and o-, m- and p-toluidines are formed. The difference in the rates of reduction can be used to obtain pure DNT isomers. Thus, when a mixture of 2,4- and 2,6-DNT is reduced with hydrogen at a pressure of 4-5 MPa and 40-50ºС in a methanol medium, the reduction of 2,4-DNT occurs and pure 2,6-DNT can be isolated from the mixture with various reduction products. Similar results were obtained using NaHS solutions in alcohol at 50-70ºС. The processes of catalytic hydrogenation can be accompanied by side reactions. The catalytic reduction of NB and its derivatives by hydrogen on Pd/C in the presence of 40% formalin leads to the corresponding dimethylalanines with a satisfactory yield [154].

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At hydrogenation of o-MNT (Pd catalyst) in aqueous sulfuric acid along with o-toluidine 2-amino-5-hydroxytoluene produces, at hydrogenation in HCl medium (125°C, 1.5-2 MPa) 2-amino-5chlorotoluene produced. At hydrogenation in a medium of a solution of sulfuric acid in methanol (catalyst Pt/C) together with o-toluidine 3- and 5-methoxy-2-aminotoluenes were obtained. When hydrogenating the nitrophenylalkyl ketones on a palladium catalyst (carrier – diatomaceous earth or CaCO3), only the nitro group is reduced, but in the solution containing CH3COOH, H2SO4 and H2O, both the nitro group and the carbonyl are reduced [155]. In the reduction of 1,3-dinitrobenzene under severe conditions (temperature 250°C, pressure H2 4.7 MPa), resorcinol is formed with a yield of 72% [156]. When o-benzonitrile was reduced to Pt and Pd, an oaminobenzoic acid amide was obtained [157]. The reduction of halogenated nitrotoluene should be carried out in the presence of Pt or Pd in order to exclude the dehalogenation reaction. The sulfides Pt, Pd, Rh, Ru, Co are especially effective, since in this case there is no poisoning of the catalyst. The yield of amines is close to quantitative. It was found that PdS is selective with respect to the chloro derivatives and is not selective in the reduction of bromine nitro compounds [157]. The reduction reaction of p-nitrodiethyl aniline (p-NDA) is of great practical importance [158], since the product of the reaction – paminodiethylaniline (p-ADA) (fig. 29) after acidification with sulfuric acid (at 203 K and pH>3) is used in photo- and film industry for the processing of multi-layer photosensitive materials (fig. 30). In industry, the hydrogenation of p-NDA is carried out under stringent conditions in methanol at skeletal nickel catalysts having pyrophoric; the reaction is characterized by a considerable duration and a high catalyst consumption. In the literature there are single sources on the hydrogenation of p-NDA, these studies are not systematic. So the implementation of the reduction reaction of p-NDA in the liquid phase in order to select a highly active non-pyrophoric catalyst and mild synthesis conditions of the corresponding amine is an actual issue.

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Figure 29 – Hydrogenation of p-NDA to the corresponding amine.

Figure 30 – Interaction of p-NDA with sulfuric acid in order to obtain a valuable product for the photographic and film industries.

It was found by results of the hydrogenation of p-NDA in a catalytic “duck” that the change in the mass of the sample of p-NDA does not affect the reaction rate; the initial reaction rate does not depend on the amount of hydrogenated material, i.e. the reaction order for the substance is zero. The activity of Pd-catalysts deposited on C is higher than for the samples of catalysts deposited on Al2O3, which agrees with a decrease in the basicity of the carrier, affecting the degree of electron interaction of the metal-carrier. By reducing the activity of the prepared catalysts are located in a row: Pd/C˃Pd/CaCO3 ˃ Pd/γ-Al2O3. The high catalytic activity of Pd-based catalysts compared to Nicatalyst allowed the reaction to be carried out under milder conditions. Enlarged tests of p-NDA in an autoclave were carried out on 2% Pd/C in methanol at hydrogen pressures of 0.5-3.0 MPa (tab. 7). The 93

large-scale tests showed the high efficiency of Pd-based catalysts compared to industrial Ni-Raney: an increase in the yield of the target product, a shorter reaction duration, a reduction in catalyst costs. The influence of the nature and position of the substituent on the rate of reduction of the nitro group in aromatic nitrocompounds was studied in [159-168]. N.D. Zelinskii and A.A. Strel’tsova [159], studying the effect of the substituents – Cl-, OH-, CH3-, CH3O-, COOH-, SO3H- groups- in the aromatic ring on the rate of hydrogenation of the nitro group on Pd/C- catalyst (at 293 K and atmospheric pressure), found, that the reduction of all substituted nitrobenzene proceeded quantitatively and almost at equal rates. The authors concluded that the nature of the substituent does not affect the rate of reaction and the yield of the amino product. In [160, 161], the authors investigated the kinetics of the reduction of monosubstituted nitrobenzene with different positions of the substituents in the benzene ring of the groups: CH3-, NH2-, OH-, CH3O-, COON-, COO2H5-, COOCH3- (over nickel catalyst at 293 K and atmospheric pressure). In all cases, the position of the substituent group and its nature exerted a significant influence on the rate of hydrogenation of the nitro group [128, 129]. Table 7 – Enlarged tests for hydrogenation of p-NDA (31.5 g) in methanol Q, amount of a Amine yield, catalyst, g %* 2%Pd/C 358 2.5 0.2 86 358 2.5 0.15 84 360 2.8 0.15 90.0 360 3.0 0.2 91.0 363 3.0 0.15 91.2 368 2.8 0.2 92.0 368 2.8 0.15 92.1 Industrial Ni-Raney 358-372 2.5-3.0 1.0-1.2 83.5-84.1 *- The yield (g) is the sum of 5 parallel experiments T, K

PH2, MPa

Reaction duration, min. 18.0 12.0 14.0 14.5 14.0 14.0 13.5 35.0- 45.0

For each group of compounds with the same substituent, the reduction rate decreased in the series: o ˃ m ˃ p [160, 161]. 94

When nitrobenzene derivatives were reduced on skeletal nickel in ethanol at 293 K and atmospheric pressure, it was established [162] that the rate constant of hydrogenation of the nitro group is different for all nitrocompounds and decreases in the following sequence: о–ОН > о–NH2 > p–OC2H5 > m–СН3 > Н > p–СH3 > p–ОН. The authors of [160] believe that the difference in the rate constants is caused by a change in the activation energy of the process as a result of the action of substituents on the active center of the catalyst. In detail, the effect of substituents on the kinetics and mechanism of the reduction of nitrobenzene on skeletal nickel, Pt- and Pd-black in 50% ethanol at 298 K and atmospheric pressure was studied in [163166]. It has been established [164, 165] that when the process is carried out on Ni-skeletal, where the activation of hydrogen is the limiting stage in the reduction of nitrobenzene, the introduction into the benzene ring of the electron-withdrawing substituents CHO-, COOH-, COONa, increasing the adsorption of nitro compounds, hinders the activation of hydrogen on the surface of the catalyst, leads to a decrease in the reaction rate. The electron donating substituents CH3-, NH2-, OH-, C2H5-, increasing the electron density in the benzene ring and the associated nitro group, decrease the adsorption capacity of the nitro compound, which causes an increase in the rate of hydrogenation in comparison with unsubstituted nitrobenzene [167]. An opposite regularity was observed by the authors during the hydrogenation of substituted nitrobenzene on Pt – black [164, 165]: the reduction was accelerated by the introduction of electronwithdrawing substituents and slowed down in the case of electrondonor substituents. The authors found when reducing substituted nitrobenzene compounds over Pd-black, that the introduction of a substituent does not significantly affect the reaction rate. The position of one and the same substituent in the benzene ring with respect to the nitro group is found in the following relationship: on skeletal nickel, the isomers in descending hydrogenation rate are arranged in a series – o- > p- > m-; and on Pd-black: – m- > p- > o-. In the work [167] the reduction of nitrobenzene derivatives with various substituents at the p- and m-position in ethanol and the 95

presence of nickel and nickel-copper-iron catalysts deposited on clay was studied. It was found that there is a linear dependence between the anodic displacement of the potential and the rate of hydrogenation, which allowed the authors to assume that the reaction under these conditions is limited by the activation of the nitro compound. Therefore, the introduction of electron-withdrawing substituents in the benzene ring NO2-, CHO-, m-OH- increases the reaction rate, and the introduction of electron-donor substituents p-OH-, CH3-, C2H5O- lowers the rate of reduction [167]. Based on these data, the authors concluded that the patterns of substituted nitrobenzene hydrogenation catalysts similar to those results obtained by the hydrogenation of these compounds on Pt – black [163]. This behavior of nickel catalysts on carriers is explained by the increased energy of the hydrogen bond with the catalyst in comparison with skeletal nickel. It was established in [168-175] that during the catalytic reduction of nitro compounds, the hydrogenation processes can be accompanied by the interaction and isomerization of the intermediate products formed during the reaction. The nature of the intermediate stages and intermediates, the selectivity and depth of reduction depend on the ratio of the rates of hydrogenation reactions and the interaction of intermediate products. The velocity values, in turn, are determined by the quantitative ratio and speed of reproduction of the reacting components on the contact surface, i.e. the nature of the catalyst, the composition of the solvent, and the temperature of the experiment. When nitrobenzene (0.204 g) is reduced over Ni-skeleton (0.3 g) in 50% ethanol at 298 K and atmospheric pressure [169, 172-175] there are sections of the minimum and maximum velocities on the kinetic curve. Nitrobenzene is significantly adsorbed on the surface of the catalyst, which hinders the activation of hydrogen and its reproduction. With an increase in the concentration of nitrobenzene from 0.098 to 0.300 g, the minimum on the kinetic curve deepens, the average reaction rate decreases. With a further increase in the nitrobenzene concentration, the catalyst is deactivated and the reduction is stopped. With a temperature change in the interval 298-323K, the reaction rate passes through a maximum of 313K. The results of the experiments indicate a practically complete

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absence of hydrogen on the surface. The apparent activation energy in the interval 298-313K is 31.8 kJ/mol. In the transition from 50% ethanol 96% reduction rate is increased (from 9.6 to 18.0 cm/ min) and the alignment of the kinetic curve. This indicates that with increasing alcohol concentration the solubility of nitrobenzene increases and its content on the surface decreases. Based on these data, the authors believe that the process of reducing nitrobenzene to Ni-skeletal in 50% ethanol is limited mainly by hydrogen activation. The minimal speed, according to the authors, is caused by the lack of hydrogen on the surface, and the maximum speed is associated with the hydrogenation of the intermediate products. To test this assumption, the authors of [176-178] added to the Ni-skeleton promoters that activate hydrogen well, in particular Pt, Pd, Rh. The test of these catalysts showed that their activity is 3 times higher than the Ni-skeleton. At the same time, the kinetic curve is equalized, i. e. the minimum and maximum disappear, and the process begins to follow the hydrogenation direction. To completely refine the route of the reaction, under similar conditions, the authors carried out the reduction of nitrobenzeneaniline intermediates: nitrosobenzene, phenylhydroxylamine, azoxy, azo, and hydrazobenzene, and found that all the intermediate products are reduced more slowly than nitrobenzene; the exception is phenylhydroxylamine, which is hydrogenated at the same rate as nitrobenzene. A comparison of the potentiometric curves showed that only nitrosobenzene is adsorbed stronger than nitrobenzene and therefore it can not be displaced into the solution by nitrobenzene. To further reduce nitrosobenzene, hydrogen is required, the renewal of which on the surface is hampered, as a result of which nitrosobenzene accumulates on the surface, the rate of further reduction decreases, and along with the hydrogenation direction reactions of the intermediate compounds begin to proceed. The phenylhydroxylamine formed under these conditions is partially displaced by the nitro- and nitrosobenzene molecules into the solution and reacts with the nitrosobenzene adsorbed on the surface of the catalyst to form azoxybenzene, which is then hydrogenated at a high rate to azo and hydrazobenzene, and then to aniline.

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Thus, the authors showed that the reduction of nitrobenzene to Niskel. can go along two routes: 1) hydrogenation direction, when the concentration of hydrogen on the surface of the catalyst is high enough, and nitrobenzene is reduced without leaving the surface directly to aniline (96% ethanol, Ni-skel., promoted and non-promoted catalysts); 2) the interaction of intermediates to form azoxy- , azo and hydrazobenzene, when there is a lack of hydrogen on the surface of the catalyst (50% ethanol, 0.1 N NaOH in 50% ethanol). Over Pt-black (0.043 g) in 50% ethanol at 298 K, nitrobenzene (0.204 g) is reduced with a constant velocity (11.3 cm3/min) [170, 175]. The anode displacement of the catalyst potential with the introduction of nitrobenzene is 190 mV and indicates that nitrobenzene removes from the surface not all of the adsorbed hydrogen. An increase in the concentration of nitrobenzene from 0.098 to 0.300g does not affect the shape of the kinetic curve, the velocity increases slightly (from 11.3 to 12.4 cm3/min), the potential displacement also increases from 165 to 200 mV, indicating an increase in the surface concentration of nitrobenzene. In the interval 278-298 K, the hydrogenation rate does not change, and at 313 K the reaction slows down. The potential displacement is reduced from 200 to 180 mV, i.e. the amount of nitrobenzene on the surface decreases. An increase in the concentration of ethanol above 50% sharply reduces the rate of reduction, and in 96% ethanol the reaction does not occur. Based on these data, authors suggested that the process of reduction of nitrobenzene on Pt-black in 50% ethanol is limited by the activation of nitrobenzene and the process proceeds along the hydrogenation direction. It has shown at the hydrogenation of individual intermediate products such as nitrobenzene, like Ni-skeletal, is reduced at a higher rate than all the intermediate compounds. It was found from the data of potentiometric measurement, that nitrosobenzene and phenylhydroxylamine are adsorbed stronger than starting nitrobenzene, so they cannot be pushed out from the catalyst surface into the solution, and in the bulk there is no accumulation and interaction of the intermediate products. Therefore, there are no kinks on the kinetic curve, in contrast to the hydrogenation curve of nitrobenzene on Ni-skeleton, i.e. the reduction of nitrobenzene on Pt98

black in 50% ethanol is carried out by the hydrogenation direction. The reduction of nitrobenzene (0.204 g) over Pt-black (0.030 g) [171, 175] in 50% ethanol at 298 K proceeds to the end at a constant rate (5.2 cm/min), as over Pt-black. The anode displacement of the potential is greater than that of Ptblack, and amounts to 220 mV, an increase in the nitrobenzene concentration does not affect the reaction rate and the magnitude of the potential displacement, on the basis of which the authors assumed that the reaction proceeds in zero order in the substance. Increasing the temperature from 278 to 313K increases the rate of hydrogenation. Further increase to 323K, as on Pt -black, reduces the rate of reactions. The apparent activation energy in the interval 278-298 K and 298-313 K is 26.8 and 16.7 kJ/mol, respectively. The transition from 50% to 96% ethanol leads to a significant acceleration of the process (the rate rises from 5.2 to 15.6 cm3/min). The authors believe that the reduction of nitrobenzene on Pd-black in 50% ethanol is due to hydrogen dissolved in palladium and the process is limited by the rate of dissolution of hydrogen in the metal, and in some cases by the rate of release of hydrogen dissolved in the palladium onto the surface. By special calculations the authors established that in a number of cases the process of hydrogen dissolution in palladium is delayed by diffusion through a multilayer adsorption film of nitrobenzene molecules and intermediate products formed on the surface of the catalyst. The reduction of nitrobenzene aniline intermediates on Pdblack in 50% ethanol at 298 K showed that all the intermediate products are hydrogenated more slowly than nitrobenzene, with the exception of azobenzene, whose initial rate of reduction is somewhat higher.

Chapter 8. The mechanism of catalytic reduction of aromatic nitro compounds created by Ya.A. Dorfman The orbital approach to the Ya.A. Dorfman mechanism is constructed in the light of modern orbital representations and is valid for the hydrogenation of the nitro group on various catalysts.

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The mechanism proposed by Ya.A. Dorfman [63, 73], is considered using the orbital theory of catalysis. The most important factors, according to the author, are the electronic configurations and energies of the free orbital and the occupied orbitals of the ground state of the active catalyst, the σ- and π-acceptor and σ- and π-donor capacity of substituents, the pH of the medium, which regulate the direction of chemical transformations of nitro compounds. In accordance with the mechanism proposed by Ya. A. Dorfman, the catalytic reduction cycle of nitro compounds consists of the following stages: – dissociation of hydrogen; – hydrogenation – NO2, – NO-groups; – hydrolysis of HO-NH. Ya.A. Dorfman assumed that nitro compounds attach three molecules along three main routes. Nitro compounds and intermediates have a polar bond of N-O and the effect of the catalyst depends on the method of substrate coordination. The first two routes (π-route and o-route) differ in the way of coordination of nitro compounds and intermediates with the catalyst. The first stage of hydrogenation is the activation of hydrogen. The condition for the activation of hydrogen is the ability of the metal to form σ-bonds with the hydrogen atom, since the latter does not form other bonds. This condition is satisfied both by copper and palladium. The next stage is the activation of the nitro group. Nitro compounds can be adsorbed and hydrogenated on three routes: – The 1 st way is by means of π-bonds of the nitro group, – The 2 nd way is through the oxygen atom, – 3rd path through the interaction of intermediates with the formation of dimers – azo- and diazo-, which occurs in alkaline media. The first path (π-route) is characteristic for contacts that activate nitro compounds and intermediates by π-coordination. The second mechanism (o-route) hydrogenates nitro compounds and intermediates on catalysts preferring o-coordination. The process on both routes starts with the activation of hydrogen and nitro compounds. The interaction between them leads to the accumulation of nitrosobenzene which is hydrogenated to phenylhydroxylamine and aniline.

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The share of the third route, apparently, grows in an alkaline environment. Hydroxyl ions catalyze the reaction between intermediates (nitrosobenzene) and aniline, leading to the formation of azobenzene, which is then reduced to hydrazobenzene and aniline. The first route, like the other two, originates from the stage of hydrogen activation. Hydrogenation begins with the stage of hydrogen activation, as a result, atomic hydrogen is formed on the surface. To convert NO2 to NH2, three hydrogen molecules are needed. The reduction of the nitro group proceeds according to the scheme (fig. 31):

Figure 31 – Mechanism of catalytic reduction of aromatic nitrocompounds by Dorfman.

The orbital theory of catalysis introduces three conditions to hydrogen activators. Oxidative addition of the hydrogen molecule will easily proceed on catalysts with electronegativity of 1.7-2.2, and low energy of promoting of the p2-state. The third condition is the ability to form σbonds with hydrogen atoms, because hydrogen does not form other bonds. These conditions can withstand mainly the elements of the VIII-group of the Periodic Table of D.I. Mendeleev. On the first route the metals, activating nitro compounds and products using the π-bonds, are active to hydrogenate. The second route (o-route) is realized on catalysts interacting with nitro compounds and intermediates through an oxygen atom. The third 101

route can be in alkaline media on low-activity catalysts. As a result, the intermediates can react with each other, and the catalyst already hydrogenates the condensation products. The next selection of catalysts is made by the second stage, in which the nitro group is activated. The order of the N-O bond and the O = N = O bond angle depends on the way the nitro group interacts with the catalyst. An analysis of the electronic structure of the nitro group shows that the nitro compounds can be coordinated with the catalyst both with the help of the π-bond and with the participation of the oxygen atom. The largest negative charge is localized on oxygen atoms. The method of coordination of the nitro group is determined by the orbital energy of the electrons of the catalyst. The oxygen atom of the nitro group tends to participate in charge-controlled interactions, and πbond, on the contrary, requires orbitally-controlled reactions. Therefore, metals prone to charge-controlled reactions will be coordinated with the nitro group through an oxygen atom, and the metals forming orbital-controlled bonds will be combined with the πbonds of the nitro group. The propensity to create charge-controlled bonds usually changes antiballically to the oxidation-reduction potential of the metal, and the efficiency of orbitally controlled bonds increases with the oxidation-reduction potential of the elements. In the VIII group, the redox potentials have the following values, eV: Fe (-0. 44) < Co (-0. 28) < Ni (-0. 25) < Ru (0. 79) < Os (0. 87) < Rh (0. 87) < Pd (0. 89) < Ir (0. 93) < Pt (0. 98). Consequently, the contribution of the orbitally-controlled interaction in this series increases from left to right, and the share of the charge-controlled interaction increases from right to left. So, on the π-route, the catalyst activates the nitro compounds, reacting with the π-bonds of the nitro group. Hence, such a path is chosen by catalysts prone to the formation of π-bonds. In the Periodic Table of D.I. Mendeleev ability to create π-bonds increases from right to left and from top to bottom. If we take into account the requirements of the first stage, then we can assume that metals of the type Pt, Pd and 102

Rh, located at the bottom of the VIII-group of the Periodic Table of D.I. Mendeleev will choose the π-route. Further selection of catalysts is done based on the transition state of the next stage. A rough estimate shows that the metals of the VIIIgroup and the I-subgroup of the periodic table Mendeleyev in the hydrogenation of nitro compounds have the following configurations (tab. 8). Hence it can be assumed that Pd and Cu act by the free orbital with a high s0 character, and the remaining metals react by vacant orbitals with an increased d0 contribution. Table 8 – Electronic configurations of metals of VIII group and I-subgroup of the D.I. Mendeleyev Periodic system Metal Fe Co Ni Cu Ru Rh Pd Os Ir Pt

Electronic configurations 3d64s2 3d74s2 3d84s2 3d104s1 4d75s1 4d85s1 4d10 5d66s2 5d76s2 5d96s1

The orbital diagram shows that the metals acting by the free s0 orbit create a symmetry inhibition at the stage of the reaction of the nitro compound with the hydrogen atom. Metals that work with a vacant d0 orbit, on the contrary, help the reaction of the nitro group with the hydrogen atom. At the next stage of the π-route, the hemihydrogenated form of the nitro compounds adds the second hydrogen atom. Then there is a noncatalytic reaction of the splitting of water from the intermediate product molecule and the formation of nitrosobenzene. After this stage nitrosobenzene (R-N = O) enters the catalytic cycle of the π-route. Nitrosobenzene is also a sufficiently polar molecule and can be coordinated through the π-bonds of N-O and the oxygen atom. In the π-route, nitrosobenzene is activated by the formation of π-bonds with the catalyst. Nitrosobenzene joins the second hydrogen molecule in 103

the same orbital scheme as nitrobenzene. Here, the lowest free dorbitals of the working catalysts also differ in favorable nodal symmetry. Catalysts acting by their vacant orbitals with a high scharacter create a barrier to the hydrogenation of nitrosobenzene to phenylhydroxylamine. After the absorption of the second hydrogen molecule, phenylhydroxylamine enters the reaction. Metals that prefer charge-controlled coordination will interact with phenylhydraxylamine through an oxygen atom. The contribution of ocordination will increase with decreasing oxidation-reduction potential of the complexing agent. Elements prone to orbitally controlled binding will adsorb phenylhydroxylamine through a nitrogen atom. And at these stages of the π-route, the catalysts acting better with free orbitals with increased d-contribution are better. The π-route ends with the reaction of hydrogenation of phenylhydroxylamine to aniline. It can be expected that the proportion of the π-route will increase with the increase in the acceptor properties of the substituents of the nitro compounds. Forecasts of the orbital theory of catalysis agree well with experimental data on the hydrogenation of nitro compounds on Pt, Pd, and Rh-catalysts. In a water-alcoholic medium, nitro compounds on such catalysts are hydrogenated to zero order without the accumulation of intermediates, and the reaction rate positively reacts to an increase in the acceptor capacity of the substituents. For π-route, the catalyst basicity condition is unfavorable. For the o-route, on the contrary, the rate increases with the enhancement of the basicity of the catalyst. The o-route begins with the activation of hydrogen. The O-route at this stage puts forward the same orbital requirements as the π-route. However, already the second stage of the O-route presents absolutely opposite requirements. For ocoordination of nitrocompounds, nitroso compounds and phenylhydroxylamine, metals preferring charge-controlled interactions, i.e., having a low oxidation-reduction potential are needed. Therefore, for the O-route, catalysts from the upper part of the VIII-group of the Periodic Table of D.I. Mendeleev are needed. In 3, 4 stages, nitrosobenzene is formed by sequential addition of two atoms of coordinated hydrogen from nitrobenzene. Orbital diagram shows that on the O-route in a more favorable position are the metals acting with free orbitals with a high S-character. 104

The reaction of hydrogenation of nitrosobenzene to phenylhydroxylamine continues the previous stage and presents similar requirements to the catalyst. For the hydrogenation of nitrosobenzene, catalysts that have in the coordinated state free orbitals with a high S-contribution are needed. For the final stage of the o-route, in which phenylhydroxylamine is converted to aniline, catalysts that release the orbitals with increased d-contribution under the influence of reagents (and also solvent, carrier) are more suitable. So, the o-route sets absolutely opposite conditions for the catalysts than the π-route. In this way, the reaction is carried out by catalysts preferring a charge-controlled combination, necessary for ocoordination, and acting by free orbitals with a high s-character required to provide reactions between hydrogen atoms and ocoordinated nitrobenzene and nitrosobenzene. The electronic structure of the nitro group is as follows: thirteen valence electrons of the NO2 molecule form the following configuration: σ2s, σ2y, π2y, 2р2, 2р2, π2y, σ1z. The first three orbitals: σ2s, σ2y, π2y are binding, the other – 2р2, 2р2, π2y, σ1z remain unbound. The total number of binding electrons is six, which corresponds to an average bond order of 1.5. The molecule has an angular shape with πbonds. At the stage of coordinating the oxygen atom of the nitro group, nitrosobenzene is formed by successive addition of two coordinated hydrogen atoms from nitrobenzene (fig. 32, a). The orbital diagram shows that in a more advantageous position, there are metals acting by means of free orbitals with a high scharacter. The nodal symmetry of the d-orbitals creates an energy barrier at the stage of addition of the first hydrogen atom to the nitrogen atom of nitrobenzene. Slightly in a better position than the sorbitals, there are d-orbitals during the addition of the second hydrogen atom to the hemihydrogenated form of nitrobenzene. On dmetals, the second hydrogen atom attacks the bonded lobe of the oxygen atom, and on the s-metals it does not. In the latter case, the reaction occurs due to the presence of an unshared pair of oxygen atoms. A busy, unshared oxygen orbit ensures the flow of this stage and reduces the energy barrier. Thus, the orbital consideration of the hydrogenation stage of nitrobenzene to nitrosobenzene shows that the 105

activation energy of the reaction is less for metals operating with free orbitals with a high s-character. Such a mechanism is quite the opposite of the π-coordination of the nitro group on Pd.

a

b Figure 32 – The mechanism of adsorption and hydrogenation of the nitro group of NB: a – nitro → nitroso; b- nitroso → phenylhydroxylamine

The next stage of hydrogenation of nitrosobenzene to phenylhydroxylamine (Fig. 32, b) is similar to the previous one. On the orbital diagram, to prove this conclusion, the operating orbitals of nitrosobenzene, hydrogen and the catalyst are shown at the stage of addition of the first hydrogen atom to nitrosobenzene and operating orbitals at the stage of addition of the second hydrogen atom to the 106

hemihydrogenated form of nitro-zobenzene. At this stage nitrosobenzene passes into phenylhydroxylamine. Hydrogenation of the coordinated phenylhydroxylamine consists in the hydrogenolysis of the O-N bond to form an amine and a hydroxyl group. Then the hydroxyl group attaches the second hydrogen atom and turns into water. Orbital consideration also satisfactorily explains this stage of the process. Thus, the mechanism proposed by Y.A. Dorfman, based on orbital modeling, helps to understand the complex nature of the action of catalysts in the hydrogenation of nitrobenzene and its derivatives and can be used in predicting the properties of catalysts and developing selective catalytic systems. LITERATURE to Part III 1. Сокольский Д.В. Гидрирование в растворах. – Алма-Ата: Наука, 1979. – 369 с. 2. Томас Ч. Промышленные каталитические процессы и эффективные катализаторы / перевод с англ. – М.: Мир, 1973. – 385с. 3. Омаркулов Т.О., Сокольский Д.В. Гидрирование под давлением водорода. – Алма-Ата: Наука, 1986. – 192 с. 4. Сокольский Д.В., Джарикбаев Т.К., Омаркулов Т.О. Влияние давления водорода на энергию связи палладий-водород // Вестник АН КазССР, 1979. – №2. – С.67-69. 5. Сокольский Д. В. Электрохимические методы исследования механизма каталитической гидрогенизации в растворах // Сб. Прогресс электрохимии органических соединений, Изд-во Наука , 1969, стр. 328 –356. 6. Брокман К. Электрохимия органических соединений. Процессы электролитического окисления и восстановления, Л.: ОНТИ-Химтеорет, 1937. – С.197-282. 7. Юнгерс Ж., Сажюс Л. Кинетические методы исследования химических процессов. – Л.: Химия, 1972. – 421 с. 8. Winsiak J., Klein М. Reduction of nitrobenzene to aniline // Ind. and Eng.Chem.Prod.Res. and Dev. – 1984. – V. 83. N1 – P. 44-50. 9. Сокольский Д.В., Друзь В.А. Потенциометрический метод исследования реакций каталитического гидрирования // Докл. АН СССР. – 1950. – Т. 73. – №5. – С. 949-950. 10. Шмонина В.П., Тарасова Д.В., Алексеева Г.К., Серазетдинова В.А. Каталитическое восстановление ароматических нитросоединений. Сообщение XII. Полярографическое исследование механизма восстановления нитробензола на скелетном никеле // Тр.ин-та /И-н-т хим.наук АН КазССР. 1952. – Т. 8. – С. 64-72.

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Part IV. CATALYSTS FOR LIQUID‐PHASE HYDROGENATION  OF AROMATIC NITRO COMPOUNDS    Currently, one of the topical areas is the development and investigation of highly efficient and selective catalysts for the hydrogenation of aromatic nitro compounds to the corresponding amines, since amines find wide application in the production of various dyes, drugs, corrosion inhibitors, stabilizers, polyurethanes, antiknock additives for gasolines and motor fuels and others [1-4]. The reduction of nitro compounds can be carried out in the presence of both homogeneous and heterogeneous catalysts [5]. In industry, widespread use of solid-phase heterogeneous catalysts [6]. This is due to the difficulty in isolating and regenerating a homogeneous catalyst [7]. Heterogeneous hydrogenation catalysts for aromatic nitro compounds can be divided into the following groups: 1) catalysts containing nickel [8-12], copper and noble metals [1323], including blacks [13-15]; 2) heterogeneous catalysts on a fiberglass woven matrix; 3) heterogeneous catalysts on a metal-polymeric matrix. An important role as a part of the catalyst is played by the carrier. As carriers for catalysts use various carbon carriers: activated carbon [24-26], carbon fiber [27], nanodiamond [28, 29], fullerene black [30], as well as various oxides such as Al2O3, SiO2, CaCO3 and etc. [16-22]; polymeric, fiberglass and other matrices [17, 31]. Recently, carbon nanomaterials have been used as a catalyst carrier: fullerenes and fullerene black, carbon nanotubes and nanofibres, nanodiamonds and graphene materials [32]. Particular interest is given to nanodiamonds (ND) and graphene-like materials. ND have unique properties: high strength, high specific surface with different functional groups located on it, which can be easily modified.

Chapter 9. Catalysts based on copper and nickel For the catalytic reduction of nitro compounds, according to P. Sabatier [33, 34], copper is the most suitable of the metal catalysts. It 119

is very easy to prepare, since it is obtained from oxide at temperatures below 180°C, it is very resistant to the action of catalyst poisons and does not affect the aromatic nuclei. Under industrial conditions, when catalytic hydrogenation is used to hydrogenate the nitro group in aromatic nitro compounds to an amino group, a copper catalyst supported on silica gel (14). The catalyst is prepared by precipitation using copper carbonate. The catalyst is reduced before use in the process in a stream of hydrogen at elevated temperatures. (14) In 1902 P. Sabatier showed that as catalysts of this reaction it is possible to use nickel and some other metals. Also in the industry nickel with additives of oxides of vanadium and aluminum is applied to hydrogenation of a nitrobenzene to aniline. Process is carried out at 250-300ºC, the catalyst can be regenerated easily by air flushing. In order that there was no hydrogenation of a benzene ring, as catalysts platinum, palladium or Reney's nickel are not applied. In any case, the process of reduction of nitro compounds is very complicated, multi-stage, with careful selection of active selective and sufficiently stable catalysts, as well as process conditions – temperature, solvent and hydrogen pressure. Most studies of the reduction of nitro compounds, as shown by the analysis of patents and literature data, are carried out using nickel catalysts [8-12, 35-41]. The most common catalyst for the reduction of various objects, including nitro compounds, is currently Raney nickel. Skeletal nickel catalyst was developed by M. Raney in 1924-1925 [7, 17, 18, 42]. It is obtained by leaching aluminum from aluminum-nickel alloys with different contents of these metals. The content of aluminum in the catalyst is small, if in the initial alloy the nickel content does not exceed 35%. However, the product obtained from the 50:50 alloy contains up to 17% Al. With increasing nickel content in the initial alloy, the size of the crystals and the rate of leaching decrease. The rupture of localized Ni-Al bonds during leaching is accompanied by the appearance of holes with a high acceptor capacity with respect to 120

hydrogen. Therefore, the amount and binding energy of sorbed hydrogen, the specific surface, the stability of the catalyst, and a number of other parameters increase. Raney Nickel, obtained from alloys of Ni with Mg or Zn, has a much lower catalytic activity in most reactions. The skeletal nickel catalyst has a structure of metallic nickel with crystal sizes of 4-8 nm. It varies little with prolonged storage under a 1% solution of NaOH. The magnitude of nickel crystals depends on the leaching temperature, increasing with the growth of the latter. This is very important, since for each hydrogenated compound there is an optimal crystal size, which, for example, for the reduction of NB is 5.9 nm, for phenol hydrogenation – 3.0 nm. In the leaching of the alloy, fine powders with particle sizes of 10-80 μm are formed, which are recommended for use in apparatus with intensive mixing. To obtain the catalyst with the maximum specific activity, the initial alloy is ground in a colloid mill to a size of 0.5-5 μm. At a partial leaching of aluminum produce alloy granules which find application in devices with the stationary catalyst. For increase in a longevity of the catalysts used in a stationary layer it is recommended to reinforce them or to place in a matrix from the easily formed material. A porous matrix is obtained from some types of clay, silica gel or alumina gel. For this, a mixture of clay and Ni-Al alloy is formed into granules and sintered at 500-1,000° C. In other cases, a 20% aqueous solution of silicate-sol is added to the Ni-Al powder and then dried, molded, heat treated and leached. The strength of the obtained catalyst for compression is 28 Pa. When the skeletal catalyst is dried in air, heating and oxidation take place. Even if the dissolved catalyst is completely removed from the catalyst after leaching under vacuum, it remains pyrophoric. When the air was blown through it under the water for 10-12 hours, a nonpyrophoric and inactive catalyst was obtained. As noted above, the reactivity of nickel is heavily influenced by leaching conditions, in particular temperature, which determine both the activity of the surface and the strength of hydrogen retention. For example, in contact with a nickel catalyst (previously leached at 50°C), NB in an inert atmosphere extracted 160 ml of H2/g catalyst, but the latter retained the ability to adsorb hydrogen and pyrophoricity.

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If the treatment of the alloy with alkali was carried out at 1,050°C, the NB recovered 135 ml of H2/g, and the catalyst lost its pyrophoricity. It should be noted that the degree of hydrogen extraction of NB is two and more times higher than that of ketones and unsaturated compounds. Upon the reduction of NB in the reaction mixture, a different amount of azobenzene is detected [43]. It is assumed that with a lack of hydrogen on the surface of the catalyst, NB displaces from the surface primary intermediate products – nitrosobenzene and phenylhydroxylamine, which, interacting with each other, form azobenzene, etc. The increase in pressure increases the concentration of hydrogen on the surface of the catalyst and contributes to the complete reduction of the NB. As noted above, along with Raney nickel, there are a number of other nickel-based catalysts. These include, first of all, nickel black and a large number of catalysts-nickel on the support (SiO2, Al2O3 and others), differing in the technology of depositing metal on the carrier, the nature of the carrier and the methods of processing the resulting compositions. The supported catalysts are widely used in processes with both a mobile and a stationary catalyst bed. A very important role in their performance (running time, longevity, activity, mechanical strength, etc.) is played by the nature of the carrier. The most common among the latter are silicon and aluminum oxides. As in the production of Raney nickel, the production of supported nickel catalysts is determined by the conditions of metal deposition, the reduction temperature of the catalyst, and the degree of saturation with hydrogen. These factors determine not only the physical but also the chemical properties of the catalyst, since they strongly influence the bonding of active atoms with the substrate material or even their entry into chemical compounds with the elements of the latter. A specific place among carrier materials is held by aluminates of calcium and cements. The main field of their use are high-temperature processes, thanks to their high heat stability and a low coking, but they are applied also at low temperatures. In the preparation of nickelcement catalysts, nickel hydroxycarbonate is mixed with calcium aluminate in water, in aqueous ammonia solution or in the form of powders and subjected to heat treatment. In this case, depending on 122

the ratio of the components, a different amount of free NiO is formed along with the disordered solid solution of NiO-Al2O3. The presence of CaO in the system promotes the existence of free nickel oxide and inhibits the formation of spinel NiAl2O4. The presence of hard-torecover compounds, despite the fact that the reduction temperature reaches 800ºС, ensures the preservation of high dispersity of metallic nickel in a wide range of temperatures. To increase activity of catalysts of this group for work at low temperatures and to reduce interaction between oxide of nickel and aluminate of calcium, alumina is entered into them. Regardless of the type of nickel catalysts (Raney nickel, nickel catalysts supported, including those with an alumina-calcium substrate, granules or a stationary layer), their activity is primarily determined by particle formation technology. In this case, the decisive role is played by the conditions for depositing nickel on the surface with an inert additive or with an additive that has promoter properties and the formation of active centers on this surface. When using a Raney nickel catalyst increase the number of acceptor substituents in the molecule aromatic nitro compounds leads to increased adsorption of the latter on the surface and reduce the rate of reduction, as they inhibit the activation of hydrogen. On platinum the inverse picture is observed. The accelerating influence of H2PtCl6 on hydrogenation o-MNT on Reney's nickel in alcohol is revealed.

Chapter 10. Catalysts based on precious metals 10.1. Palladium catalysts in the processes of catalytic hydrogenation of nitro compounds 10.1.1. Structure of palladium catalysts Palladium is of particular interest for theoretical chemistry due to its position in the periodic table: it is the only element with the electronic configuration d10s0p0, which can vary depending on the type of chemical binding and determines the specific behavior of this metal. The role of palladium in catalytic reactions is largely determined by the different structure of active sites on its surface. Establishing the structure of active sites by experimental methods is difficult, and therefore it is widely used for the quantum-chemical modeling of 123

microcrystals or palladium clusters [44-49]. Calculations via the Advanced Huckel method (AHM) [44-46] and density functional method [47-49] showed that small clusters Pdn (n = 2-15) can have both a flat [45] and a three-dimensional structure [45-49]. The lengths of Pd-Pd bonds in clusters vary within the range of 2.6-2.8 Å. Table 9 presents optimized AHM structures of Pdn clusters [44]. As can be seen from these data, the stability of clusters, characterized by the binding energy attributed to the number of Pd atoms (E bond/atom), increases with the number of atoms in the cluster, as well as in the transition from planar structures to bulk ones. As the cluster size increases, the energy gap between the higher occupied and lower free molecular orbitals of clusters decreases (HOAO, Highest Occupied Atomic Orbital and LMOs, Loosening Molecular Orbitals molecular orbitals, respectively). The charge in clusters Pd is distributed between all atoms. Clusters with n = 4 are electrically neutral. Maximal absolute charges (-0.014, -0.008 and -0.011 atomic electric charge, a.e.c.) have central atoms in clusters with planar structure Pd5, Pd6 and Pd7 (I-5, I-6 and III-7 in tab.9). In the most stable clusters with high symmetry, the electron density is distributed more uniformly and the charge on the atoms does not exceed +0.005 a.e.c. The only exception is the central atom in the icosahedron with a charge of -0.01 a.e.c. The "surface" atoms in these clusters have very small charges not exceeding ± 0.001 a.e.c. [45]. The formation of cations and anions in the interaction of Pd with a carrier strengthens small clusters. Negatively charged clusters tend to form a bulk structure, whereas positively charged ones are predominantly flat, so three-dimensional structures are most likely formed in catalysts with a donor substrate, whereas electronwithdrawing carriers should contribute to the formation of a planar configuration [46]. However, these configurations have close energies and can easily transform into one another, as evidenced by low values of the activation barriers of these transitions, which vary in the range 0.3-2 eV for clusters comprising 6 to 15 atoms [47].

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Table 9 – Some structural and energy characteristics of Pdn clusters (n = 4-7, 9, 13) [44, 45] n 4

Parameter Structure

I

II

III

0.138 -11.34

0.139 -11.50

0.144 -11.50

5

Ebond/atom, eV EHOAO, eV Structure

0.105 -11.32

0.166 -11.46

0.167 -11.40

6

Ebond/atom, eV EHOAO, eV Structure

0.147 -11.19

0.182 -11.46

0.172 -11.39

7

Ebond/atom, eV EHOAO, eV Structure

0.181 -11.37

0.195 -11.44

0.167 -11.28

9

Ebond/atom, eV EHOAO, eV Structure

Ebond/atom, eV

0.195

0.208

0.186

125

13

EHOAO, eV Structure

-11.29

-11.22

Ebond/atom, eV EHOAO, eV

0.229 -11.23

0.230 -11.24

-11.31

The modeling of clusters applied to activated carbon showed [49] that Pd forms particularly strong bonds with unsaturated carbon atoms (fig. 33). As the cluster size increases, the strength of Pd-C bonds increases. With a low content of palladium, its atoms on the surface of the coal are positively charged due to the strong donor-acceptor interaction with the p-system of the substrate. With an increase in the Pd concentration, the deficit of the 4d electron density decreases and the positive charge of the palladium atoms decreases.

849.4 816.4 1,003.2

966.0 1,131.5 1,288.7 Figure 33 – Optimized structures (DFT) and corresponding binding energies (kJ mole-1) of Pdn/C10H6 clusters [44, 49]

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10.1.2. Activation of hydrogen on active centers of palladium catalysts and the role of different forms of hydrogen in hydrogenation As is known, the first stage of catalytic hydrogenation is the adsorption of hydrogen and substrates on the surface of the catalyst (see Part II, Chapter 3) [50-59]. Regarding the forms and methods of activating hydrogen on the active centers of hydrogenation catalysts in the literature there are different view points [60-71]. The relative inertness of hydrogen is due to the high dissociation energy of its molecule (432.9 kJ×mol-1). The bond between the H2 atoms can be weakened by donor-acceptor coordination with a metal in which hydrogen can act as both a donor and an electron acceptor to form charged particles of H2δ+ and Н2δ-, whose dissociation energies (259.6 and 77.9 kJ×mol-1, respectively) is much lower than the dissociation energy of the H2 molecule [60, 61]. The possibility of spontaneous heterolytic disintegration of molecular hydrogen on catalysts on the basis of the transitional metals is experimentally established [72]. On the metal surface there are at least four hydrogen forms having different reactivity in liquid-phase hydrogenation processes: weakly bound molecular H2δ+, as well as tightly atomic hydrogen: ionized H2δ+, Н2δ- and unionized H between which is set the adsorption equilibrium [62, 73-75] (fig.34):

Figure 34 – Adsorption equilibrium of hydrogen in the process of liquid-phase hydrogenation: H2(g) and H2(sol) – hydrogen in the gas phase and in the solution, H2ads, Н2δ+ads, Н δ-ads, Нδ+ads – molecular and atomic hydrogen on catalyst

The values of adsorption, charges, binding energies and the ratio of different forms of hydrogen depend both on the nature and dispersity of the catalyst, and on the nature of the solvent [14, 72, 7479]. In addition to these forms, dissolved hydrogen is present in the volume of the metal, which penetrates into the crystal lattice of palladium through sites adsorbing weakly bound molecular forms 127

(adsorption heat of 7 kJ×g-atom-1). Calculation of the thermal effects of all stages of hydrogen sorption based on the results of the microbalance experiment showed that the dissolution of hydrogen in palladium is energetically more favorable (activation energy 15 kJ×gatom-1) than its migration along the surface to centers with a higher heat of adsorption (activation energy 55 kJ×g-atom-1) [80]. During dissolution, a multicenter bonding of hydrogen to palladium can take place [70, 76], in particular, in the case of the Pd/Al2O3 catalyst, up to 5 hydrogen atoms can be adsorbed on one Pd atom [76]. The method of heat sorption on a palladium wire showed that hydrogen is first adsorbed at centers with a high binding energy Pd-H (adsorption heat of 60-120 kJ×g-atom-1) without dissolution. Then, areas of the surface are filled with a low heat of adsorption (30-60 kJ×g-atom-1), and only then hydrogen dissolution begins [76]. The behavior of palladium in catalytic processes is associated with different geometric structures of the active centers of its surface. Despite the great progress in the experimental methods of studying catalysis and surface phenomena, the structural features and the role of active centers of different structures in the elementary stages of the catalytic reaction can not be fully elucidated only by experimental means. According to D.V. Sokolsky [62, 63], hydrogen on the surface of metals exists in a "predissociative form", in which the H-metal bond is stronger than the H-H bond. The results of quantum chemical calculations, which were carried out later, are consistent with this statement. Thus, in [81-83], based on the DFT calculations, a model of H2 dissociation on the palladium surface was constructed. Analysis of the transfer of electrons and total energy for Pd2-H2 and Pd5-H2 systems with different geometries showed the presence of a predissociative state on the Pd surface corresponding to the stretched adsorbed hydrogen molecule [81]; in addition, in [82, 83], the presence of atomic dissociative adsorbed hydrogen and the possibility of physical adsorption of H2 have been established. The adsorption energy and the H-binding force increase with decreasing cluster size. Palladium clusters with atomic hydrogen are more stable than with molecular ones. This is confirmed by the data

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of [45, 84], where the adsorption energies of various hydrogen states on Pdn clusters (n = 1-4) are calculated. The state of the adsorbed hydrogen can be related to the location of the adsorption center in the Pd crystal. For example, in [85] it was shown that on the low-index faces of Pd (111), (100) and (110) (fig. 35), hydrogen is adsorbed only dissociatively, and molecular hydrogen can also be present on the Pd (100) face. On the stepped surface of Pd (210), both hydrogen atoms and its molecules are chemisorbed, and on the free surface the H2 molecule dissociates spontaneously, without overcoming the energy barrier, and an activation barrier appears on the surface filled with hydrogen, and hydrogen can exist in a chemisorbed metastable molecular condition. The atoms of dissociatively adsorbed hydrogen can be electrically neutral, and also carry a partial positive or negative charge [84], depending on the position of the adsorption center on the Pd surface.

Figure 35 – Low-index faces of a palladium crystal [85]

The simulation results presented in [84] show that the most unstable is the positively charged "top" shape (fig.36), which has the lowest adsorption energy. The instability of the top form is also evidenced by the interaction energies of the H atoms with different adsorption centers of the Pd clusters, determined on the basis of the analysis of Potential Energy Surfaces (PES) in [86-88]. The results of quantum-chemical modeling show that hydrogen on the surface of palladium-containing catalysts can exist in both molecular and atomic charged or uncharged forms. Atomic hydrogen, being adsorbed on various adsorption centers, can carry a different charge in sign. It is important to note that there are experimental proofs of participation in a hydrogenation of the strongly bound to the surface of the palladium catalyst of atomic hydrogen [76, 78, 89]. The metal involved in the catalytic process can act as a hydrogen electrode and 129

dissociate adsorption of atomic hydrogen [76]. Despite the fact that the strong adsorption of hydrogen in the near-surface layers of palladium is small, the relative content of strongly bound hydrogen on palladium is large and increases when it is fixed on a carrier [77].

Figure 36 – Location of adsorption centers in a three-layer model of the Pd surface [84]

10.1.3. Hydrogenation of the nitro group in nitrobenzene on Pd supported catalysts Studies in [22, 90-99] were carried out in two directions: selection of the carrier and modification of the active phase by transition metals. Table 10 gives data on the hydrogenation of nitrobenzene on palladium catalysts deposited on zeolites HY, HZSM-5, MCM-41, and on Pd/Al2O3 catalysts. The deposition of palladium on zeolites results in a sharp decrease in the reaction rate and an increase in the duration of the process, except for HY. By decreasing the activity, these catalysts are arranged in a series: Pd/Al2О3 > Pd/HY > Pd/HZSM-5 > Pd/MCM-41 On the first and third catalysts, nitrobenzene is selectively converted to aniline in 100% yield. HY and MCM-41 undergo partial hydrogenation of the aromatic ring, and up to 7% of cyclohexylamine is found in the products (tab.10). Although the activity of the zeolite-containing catalysts is less than that of the supported alumina, their stability is greater than that 130

of those supported on alumina. Thus, the addition of additional weighed portions to one sample of the catalyst does not change the reaction rate: for HY up to 12 portions (samples) of NB, for HZSM-5 – up to 12 portions of NB, and for MCM-41 – 9 portions (samples) of nitrobenzene. All the data given refer to catalysts with an active phase content of 4%. The activity of catalysts with 1% palladium decreases sharply in the case of aluminum oxide, and on zeolite-supported catalysts – only 2-3 times. The authors suggested that this is probably due to a different distribution of palladium on the carrier surface, since zeolites are characterized by high porosity and large pore sizes, especially mesoporous zeolite MCM-41. Thus, the Pd/HY catalyst demonstrated both good activity and selectivity, as well as the ability to hydrogenate the aromatic ring. Table 10 – Hydrogenation of nitrobenzene on Pd catalysts at 1.0 MPa and 298 K Catalyst 4% Pd/Al2O3 4% Pd/HY 4% Pd/HZSM-5 4% Pd/MCM-41 1% Pd/Al2O3 1% Pd/HY 1% Pd/HZSM-5 1% Pd/MCM-41

Speed, cm3/min 225 202 62 53 58 48 25 18

Duration, min. 5 7 32 35 20 30 75 98

aniline 100 93 100 97 100 99 100 99

Yield,% cyclohexylamine 7 3 1 1

As modifiers, the authors of [91-93] chose more affordable, cheap transition metals Fe, Ni, Cu, Cr, Ce. The preparation was carried out by co-precipitation of the salts of these metals on a carrier. The ratio of the active phase: the modifier varied from 1: 9 to 9: 1. With the exception of Ni and Cr, an increase in the metal content above 2-3 leads to the suppression of the reaction under the experimental conditions. Table 11 gives the results for the hydrogenation of nitrobenzene on modified catalysts supported on alumina and on unmodified Pd/Al2O3. It was found that the unmodified Pd/Al2O3 exceeds the modified catalysts by the reaction indices. Naturally, the higher the 131

palladium content, the higher the reaction rate. The least active additive was copper (speed-15-20 cm3/min, duration – 95-108 min), and the most active – nickel and chromium. Modified catalysts by activity can be arranged in the following order: Pd/Al2О3 > Pd-Cr/Al2О3, Pd-Ni/ Al2О3> Pd-Ce/Al2О3 >Pd-Fe/ Al2О3 > Pd-Cu/Al2О3 The authors noted that nitrobenzene was not fully hydrogenated on the modified catalysts, 76-95% aniline was detected in the final sample, and aniline yield of 100% was found only on Pd-Cr and PdNi catalysts. Taking into account the good activity of the carrier HY and the Cr metal, the authors prepared Pd-Cr (7: 3)/HY. The aromatic ring on this catalyst was hydrogenated by 5% (tab.11). Table 11 – Hydrogenation of nitrobenzene on modified Pd catalysts at 0.1 MPa and 298 K Catalyst Pd/Al2O3 Pd-Fe(9:1)/Al2O3 Pd-Fe(8:2)/Al2O3 Pd-Cu(9:1)/Al2O3 Pd-Cu(8:2)/Al2O3 Pd-Ce(9:1)/Al2O3 Pd-Ce(8:2)/Al2O3 Pd-Ni(9:1)/Al2O3 Pd-Ni(5:5)/Al2O3 Pd-Cr(9:1)/Al2O3 Pd-Cr(7:3)/Al2O3 Pd-Cr(7:3)/HY

Speed, cm3/min 225 28 22 20 15 32 28 65 48 62 56 50

Duration, min. 5 80 86 95 108 75 88 35 65 30 42 49

aniline 100 895 90 82 75 80 76 100 100 100 95 90

Yield, % cyclohexylamine 5

10.2. Hydrogenation of aromatic nitro compounds of various structures on platinum group metals Catalysts based on metals of the platinum group: metal black [1315] and supported catalysts [22, 23, 100] have found wide application for the production of amines.

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Catalytic systems based on platinum group metals deposited on various sorbents reveal higher activity and stability than nickel catalysts. In the earliest works (50-70 years of XX century) the catalyst, regardless of its composition, was used in amounts equal to or exceeding several times the amount of hydrogenated nitro compound. It should be noted that the black metal due to their properties, did not find practical application in the production of amines. At the same time, platinum metals deposited on various carriers, even at low contents, show high activity and selectivity of action during the reduction of aromatic nitro compounds [101, 102]. Despite the high cost, the catalysts based on platinum group metals are widely used in the hydrogenation of organic compounds, in particular, for the production of aromatic amines from the corresponding nitro compounds. A special role in this is played by the catalysts of the platinum group deposited on various carriers [103].

The reduction of 3,4-dichloronitrobenzene in the presence of iridium and platinum catalysts was studied in [104] and it was established that the limiting stage of the process is the step of converting the corresponding arylhydroxylamine into an amino compound. The orders of the reaction along the substrate and hydrogen are calculated, and the optimum process conditions are determined. Hydrogenation of aromatic mononitrocompounds in the flow regime on supported porous catalysts of the platinum group was studied in [105]. The stages of reduction of the hydrogenated nitro compound in the amine are determined, the formation of the corresponding arylhydroxylamine is intermediate. The rate constants are calculated taking into account the internal diffusion of the reagents in the pores of the carrier particles. It is determined that the limiting stage of the process is the hydrogen diffusion in the pores of the catalyst until the initial nitro compound is completely consumed. Only in the case where the active metal is 0.2-0.3% and the catalyst particle size is less than 100 μm, the reaction proceeds in the kinetic region. Platinum and palladium catalysts deposited on coal showed high activity and stability in the reduction of nitrobenzene, nitroanilines, pand o-nitrophenols and other nitro compounds with various substituents [106-111]. 133

Palladium-containing catalysts differ significantly in properties from catalytic systems based on other metals of the platinum group, as well as Ni or Cu [112]. Pd-based catalysts are one of the most effective catalytic systems for the hydrogenation of double (also conjugated) and triple bonds. In cases where it is necessary to hydrogenate only nitro groups in aromatic nitro compounds, without affecting the double bonds of the aromatic ring, it is necessary to use Pd systems [113-115]. The hydrogenation of p-nitrobenzoic acid and its salts on Pd, Rh, and Ru catalysts at atmospheric and elevated hydrogen pressures was studied in [116]. It was found that the most efficient and selective catalyst for the reduction of the nitro group is Pd/C. The activity of 0.5% palladium catalysts is directly dependent on the composition of the carrier (sorbent) and decreases in the series: Pd/C> Pd/ γ -Al2O3> Pd/SiO2 > Pd/CaCO3 An extensive study (on the example of the reduction of more than 20 nitro compounds) on the activity of Pd/C and Pd/Al2O3 catalysts in the synthesis of amines in ethanol, hydrogen pressure of 0.1 MPa and a temperature of 450 ° C is described in [117]. Quantum-chemical calculations of substrate molecules are carried out and proportional dependences are presented which describe the effect of the electronic structure of the substituent on the rate of hydrogenation. The authors indicate that the carrier plays no special role in this case, and the curves of the reduction rates of compounds and the numerical values of the velocities on the catalysts of both types are similar. Numerous studies have shown that the composition and structure of the carrier play an important role in the synthesis of catalysts, especially with small contents of the active component. Thus, at hydrogenation over a palladium catalyst [118, 119] the selectivity of the process depends on the specific surface area and porosity of the support. In [120], the reduction of nitrobenzene in alcohols and hydrocarbons on ordinary Pd/C and palladium-containing porous anionite of APA in which the cross-linking agent had different contents was studied. The authors found that the degree of crosslinking depends on the efficiency of the catalysts, the rate of reaction, 134

the influence of the swelling time of the polymer matrix, while the type of solvent does not change either the yield of the product or the rate of the process. The authors of [121] carried out the hydrogenation of aromatic nitrocompounds in organic solvents on a catalyst-ionite based on highly dispersed palladium. A high (up to 100%) degree of conversion of unsaturated compounds at 20-45º С and РН2 = 0.1 MPa is noted. The reaction orders are calculated: on the substrate zero, on the catalyst and hydrogen – the first. A directly proportional dependence of the hydrogenation rate on the degree of swelling of the polymeric support in the solvent was found. It was shown in [122] that palladium-containing anion exchangers in hydrogenation of nitro compounds in organic solvents at 0.1 MPa H2, 20-50°C are more selective and stable than Pd/C, most of all this was manifested during the hydrogenation of complex compounds. The reduction of nitro compounds of various structures on palladium-containing catalysts deposited on MgO and MgCO3 was studied in [123]. Some authors used as a carrier calcium compounds: CaCO3 and CaF2 [124] or barium-BaSO4 [125, 126]. At present, research is actively carried out in the field of the development of new catalytic systems [127, 128]. The researchers are searching for new catalyst compositions for hydrogenation processes based on nanoscale metals [129], prepared by the latest methods, using different carriers. To obtain active and selective catalysts, the procedure for modifying the catalysts is used. In a work [130] modern trends in the development of methods for constructing catalysts are considered. It is noted that the modern period is characterized by the transition from purely homogeneous or heterogeneous catalytic contacts to the use of multiphase homogeneous, heterogenized homogeneous, homogenized heterogeneous catalytic systems. The reduction of aromatic nitrocompounds on bimetallic supported catalysts was studied in [131 – 133]. It is established that the addition of a second metal to Pd or to Pt increases the activity of the catalysts. The highest activity was observed in Pd-Pt and Pd-Cu (9:1) catalysts. When Ru was added, there was no significant change in the activity of the catalyst. In the reduction of o-nitroanisole and nitrobenzene, the monometallic catalysts deposited on Al2O3 were inactive. Also, the authors note that the addition of Rh to Pd in an 135

amount up to 40 atomic% has practically no effect on the process of reduction of nitrobenzene in ethanol. At the same time, by the author of a work [22] the sequential hydrogenation of nitro groups and an aromatic ring to form cyclohexylamine was established at reduction of nitrobenzene in isopropanol at an elevated hydrogen pressure and a reaction temperature of 30-60ºC on Rh, Rh-Pt and Rh-Pd catalysts deposited on Al2O3. The results of the experiment confirmed the hypotheses of many researchers about the positive effect of the second metal in twocomponent catalysts on the kinetics of reduction of aromatic nitrocompounds and the dependence of the mechanism of the process on the catalyst composition and process conditions. It was shown in [134] that when Pt was added to Pd/C, a more active and selective catalyst was obtained for the reduction of onitrophenol. Addition of Pt to Pd [135] to 25 at.% at the synthesis of catalysts leads to a decrease in the rate of the reduction reaction of compounds with a weak adsorbing capacity and, conversely, significantly increases the rate of the process in the case of hydrogenation of aromatic nitro compounds with good adsorption capacity. An important role in the composition of the catalyst is played by the carrier. In industry, catalysts based on various carriers are used: activated carbon, aluminum oxide, pumice, sibunite, etc. Recently, carbon nanomaterials have been used as a catalyst carrier: fullerenes and fullerene black, carbon nanotubes and nanofibers, nanodiamonds and graphene materials. For example, hydrogenation of various organic compounds was studied in [136]: nitrobenzene, p-nitroaniline, p-nitrophenol, pnitrobenzoic acid, cyclohexene, hexene-1, allyl alcohol, acrylic, methacrylic, crotonic and cinnamic acids, N- propylene-4aminobenzoic acid, chlorobenzene, bromobenzene, iodobenzene, o-, m-, p-dichlorobenzenes under mild conditions (T = 318 K, PH2 = 0.1 MPa, solvent – ethanol) in the presence of palladium-containing carbon nanomaterials (nanodiamonds, graphite oxide , modified with amines). The author developed a new method for the reduction of organic compounds, which is based on the process of their hydrogenation by molecular hydrogen in the presence of palladium-containing graphite 136

oxide, functionalized with ethylenediamine, diethylenetriamine and triethylenetetramine. It was found that the increase in the chain length of the modifying amine increases the reaction rate. It was is shown that the metal activity in catalytic systems based on nanodiamonds (ND) is higher than in palladium-containing activated carbon by a factor of 1.4-1.7 in the hydrogenation of unsaturated substrates and 2-3 times in the reduction reaction of the nitro group in nitrobenzene and its para-substituted analogues. Catalysts based on nanodiamonds and functionalized graphite oxide (FGO) showed high stability in hydrogenation. When hydrogenating sequentially 5 portions of nitrobenzene without separating the catalyst and the product of reduction, the reaction rate constant remains constant within the measurement error, unlike palladium-containing activated carbon (Pd/C), in which the hydrogenation rate constant of each successive portion of the substrate gradually decreases to 30% concerning the first cycle. By a complex of physicochemical methods for analyzing of Pd/ND and Pd/FGO catalysts has been shown the presence of functional groups on the surface of the support that lead to the strong fixation of palladium nanoclusters, so that samples based on nanocarbon materials exhibit high activity, stability and selectivity in hydrogenation reactions compared to Pd/C. It was established that, regardless of the nature of the support, the main active metal form in the catalysts used in the liquid-phase hydrogenation reactions of organic compounds containing a nitro group, C = C C = N- and C-Hal bonds, is zero-valent palladium. 10.3. Hydrogenation of the nitro group and aromatic ring in nitrobenzene, p-, m-, o-nitroanilines on Pd and Rh-containing catalysts It is known [22, 137] that the best catalyst for the hydrogenation of the nitro group in nitro compounds is Pd, and for the hydrogenation of the aromatic ring is Rh [22, 138-141]. With this in mind, the authors of [97, 99] developed bimetallic PdRh catalysts for the hydrogenation of both the nitro group and the aromatic ring in aromatic nitro compounds. The ratio of components ranged from 1: 9 to 9: 1. For comparison, the results of hydrogenation of nitrobenzene (NB), nitroanilines (HA) are given. 137

On Pd catalysts, the listed nitro compounds are hydrogenated at a good rate and 100% yield of the corresponding aromatic amines (tab.12). In this case, the aromatic ring is not reduced, except for the reduction of NA at a pressure of 6.0 MPa. When nitro compounds are reduced on the Rh catalyst, the reduction rate is much lower, the process time is longer and a higher temperature is required for reduction. In this case, the aromatic ring is hydrogenated (up to 1314% for NA and up to 90% for NB). The reduction of NB to cyclohexylamine (CHA) on bimetallic Rh-, Rh-Pd, Rh-Pt and Pd-Ru catalysts was studied [97-99, 142]. By decreasing the yield of the CHA, the catalysts form a series: Rh-Pt(9:1) (97-99%) > Rh-Pd(9:1) (93-95%) > Rh (90-92%) > Rh-Pd(1:1) (84-87%) > Pd-Ru(1:1) (60-62%). Table 12 – Reduction of NB, NA on a Pd/Al2O3 catalyst at T = 293K, PH2 = 1.0 MPa in isopropanol

Compound NB m-NA p-NA m-NA p-NA o-NA m-NA p-NA

Technological parameters of a process РН2, MPa

Т, К

Wstarting, mmol/ min.

6.0 6.0 6.0 5.0 5.0 6.0 6.0 6.0

293 293 293 323 323 333 333 353

18.2 10.12 12.72 9.43 9.12 8.26 8.56 9.38

Durati on, min. 12 18 14 31 22 24 25 22

Yield of amines, % Arom Alicyc atic lic 100.0  100.0  100.0  100.0  100.0  95.0 5.0 94.0 6.0 92.0 8.0

Catalysts of composition Rh-Pd (1:1) and based on Ru are quickly deactivated. Ru-containing catalyst is the least active (yield of CHA 68-70%). The most selective catalysts for the preparation of CHA from NB are catalysts of the composition Rh-Pd (9:1) and Rh-Pt (9:1). The reduction of NA is studied on Rh, Rh-Pd catalysts. When the reduction of NA on Rh-Pd catalysts with a ratio of active metal phase 1:1, 9:1, 1:9, the yield of alicyclic amine is from 50 to 70% (tab.13). It was found that the catalysts of the composition Rh-Pt (9:1)/Al2O3 – the most selective in the synthesis of CHA from NB [97-99, 142-145]. 138

Catalysts of the same composition were tested during the reduction of NA. It has been found that at the reduction on the Rh-Pt catalysts supported on Al2O3 the yield of diaminocyclohexane (DACH) was 224%, on catalysts of the same composition deposited on SiO2, 15-40% of DACH was formed. On catalysts of 2% Rh-Pt (9:1)/Al2O3 and 3% Rh-Pt (9:1)/ Al2O3, the reduction of the aromatic ring does not occur (tab.14). For the Rh-Pt catalyst, the influence of the carrier nature on the process speed and the yield of the desired product was investigated. Inorganic oxides of Al2O3 SiO2, MgO and zeolites of the type HY, HZSM-5 were used. Table 13 – Reduction of nitroanilines (A3H2 = 800 cm3) in isopropanol. NA-nitroaniline, PhDA-phenylenediamine, DACH-diaminocyclohexane

Catalyst

4% Rh

5% Rh

Pd-Rh(1:1)

Pd-Rh(1:9)

Pd-Rh(9:1)

NA ompompompmpopomppmpp-

Technological Wstarting, Durati Yield parameters of a process mmol/ on, min. min. PhDA DACH РН2, MPa Т, К 4.0 313 3.28 22 98.0  4.0 313 4.07 21 98.0  4.0 313 3.56 18 99.0  6.0 343 5.13 28 90.0 10.0 6.0 343 4.57 31 88.0 12.0 7.0 333 5.12 28 89.0 11.0 4.0 353 5.24 20 99.0  4.0 353 7.12 19 99.0  4.0 353 7.24 17 99.0  5.0 343 7.00 24 87.0 13.0 5.0 343 8.03 22 86.0 14.0 5.0 353 6.87 18 52.0 48.0 5.0 353 7.81 26 40.0 60.0 5.0 353 6.12 28 42.0 58.0 5.0 353 5.86 24 37.0 63.0 5.0 353 6.83 23 30.0 70.0 6.0 353 6.94 23 31.0 69.0 5.0 353 7.23 32 43.0 57.0 5.0 353 8.04 30 41.0 59.0 6.0 343 6.,50 34 41.0 59.0

139

By decreasing the rate of complete reduction of nitrobenzene and nitroanilines, these carriers are arranged in the following order: Al2O3> MgO> SiO2> HY> HZSM-5, on the yield of aromatic amine in a row: Al2O3> MgO> HY> SiO2> HZSM-5, on the yield of alicyclic amine in a row: HY> HZSM-5> SiO2> MgO> Al2O3. The maximum yields of the aromatic amine are 99%, and the alicyclic amine is 70%. Table 14 – Reduction of m-nitroaniline (A3н2 = 800 cm3) on Rh catalysts in ethanol

Catalyst

Technological parameters of a process РН2, MPa

2%Rh-Pt(9:1) 3%Rh-Pt(9:1) 4%Rh-Pt(9:1) 4%Rh-Pt(9:1) 4%Rh-Pt(9:1) 4%Rh-Pt(9:1) 5%Rh-Pt(9:1) 5%Rh-Pt(9:1) 5%Rh-Pt(9:1)

1.0 1.0 1.0 1.0 1.0 2.0 1.0 2.0 2.0

Rh-Pt(9:1) Rh-Pt(9:1) Rh-Pt(9:1)

1.0 1.0 1.0

Т, К

Wstarting, mmol/ min.

Carrier – Al2О3 353 4.2 353 4.5 353 5.0 373 5.2 383 6.0 373 5.8 353 7.05 373 7.6 383 8.0 Carrier – SiO2 353 6.0 373 6.5 383 6.7

Durati on, min.

Yield, % PhD A

DAC H

80 70 65 60 50 44 50 40 30

100 100 98.5 98.0 96.0 94.0 96.0 88.0 76.0

  1.5 2.0 3.5 6.0 4.0 12.0 24.0

42 40 40

84.0 76.0 60.0

15.0 23.5 40.0

10.4. Study of the hydrogenation of nitrophenols and nitroanilines under various process conditions on Pd, Pd-Pt, PdCu catalysts The hydrogenation of nitrophenols and nitroanilines was studied in [90, 91, 93, 94, 97-99, 144, 146, 147] with a wide variation of technological parameters of the process. Reduction of aromatic mononitro compounds was started with the selection of the solvent. It was 140

found that isopropanol is the most suitable for hydrogenation of NP and p-NA on the Pd catalyst among the solvents used in the work (distilled water, C2-C5 alcohols), and ethanol is the most suitable for hydrogenation on Pd-Pt, Pd-Cu catalysts. These solvents were later used to study the hydrogenation process at various pressures and temperatures. Chromatographic analysis showed that the mechanism of conversion of aromatic nitro compounds (hydrogenation) is identical for all solvents. When distilled water and C4-C5 alcohols were used, the lowest yields of the corresponding aromatic amines were observed upon reduction of nitro compounds on Pd-Pt catalysts. When using isopropanol for these catalysts, the yield of the desired amines decreased due to side reactions, in particular, further continuation of the aromatic ring reduction process. Thus, hydrogenation of NB in the final sample, in addition to aniline, a cyclohexylamine product of hydrogenation of the aromatic ring (4-6%) was already revealed at room temperature, and with increasing temperature the content of cyclohexylamine increased to 8-10%. At hydrogenation of NB, NA and NP on Pd catalysts only the hydrogenation of nitro groups was noted, regardless of the solvents and the experimental conditions used. The yield of aniline was 96-99%, p-phenylenediamine 98%, paminophenol 89-96%, o-aminophenol 86-92%. As an example results of hydrogenation of p-NA on Pd-Cu/C catalyst in various environments (fig.37) are presented. For comparison, the authors studied the hydrogenation of nitrobenzene and aromatic nitro compounds of various structures under identical conditions. On fig.38 the kinetic curves hydrogenation of NB, NA and NP are presented. The shape of the kinetic curves when the structure of the aromatic nitro compound is changed practically does not change. It was found that the hydrogenation rate of p-NA is lower than the hydrogenation rate of NB. Even lower reduction rates on the Pd catalyst were observed during hydrogenation of NP – they are much lower than the rate of hydrogenation of NB. The studied nitro compounds on decreasing the initial hydrogenation rate form a series: NB> p-NA >> p-NP> o-NP.

141

Figure 37 – Hydrogenation of p-NA at Pd-Cu/C catalyst in various environments at (0.01 g) at 0.5 MPa, T = 20ºC: 1-ethanol, 2-iso-propanol, 3-propanol, 4- distilled water

The sharp decrease in the rate of hydrogenation in aromatic nitrophenols, compared with nitrobenzene, is apparently due to a decrease in the adsorption capacity of o- and p-NP, especially in the case of o-NP. It is obvious that the appearance of OH group substituents in the molecule in the case of the NP and NH2-group in NA-decreases the hydrogenation rate of the compounds. Amino groups-electron donors, being in the molecule, increase the electron density in the nitro group, and this effect manifests itself more strongly in the p-position than in the m-position [148]. Figure 39 shows the curves of the reduction of o-NP on various catalysts. According to the initial reaction rate, the most active catalyst is Pd/γ-Al2O3. The effect of the support is seen from Cu-containing catalysts: Pd-Cu catalysts show different rates and different selectivities (fig.39, curves 1 and 5). The lowest reduction rates and a lower yield of o-AP are found on monometallic Pd and Pt catalysts deposited on coal. On these catalysts, the calculated amount of hydrogen is not absorbed and the greatest reaction time is seen. Catalysts of composition Pd/C and Pt/C are less than others suitable for this process. The effect of hydrogen pressure on the process speed 142

and efficiency of the catalytic action of synthesized catalysts was studied. As an example, kinetic curves for the reduction of p-NP at hydrogen pressures of 0.5-2.5 MPa are presented (fig.40).

Figure 38 – Hydrogenation of aromatic mono-nitro compounds of various structures on Pd/γ-Al2O3 (0.02 g) at 0.5 MPa, T = 20°C: 1-o-NP, 2-p-NP, 3-p-NA, 4- NB.

Figure 39 – Reduction of o-NP on mono- and bimetallic catalysts (0.01 g) in ethanol at 0.5 MPa and 20ºC: 1 – Pd-Cu/C; 2-Pd/γ-Al2O3; 3-Pd/C; 4 – Pd-Pt/γ-Al2O3; 5 – Pd-Cu/γ-Al2O3; 6 – Pt/C

143

Figure 40 – Hydrogenation of p-NP at different hydrogen pressures on Pd-Cu/C (0.02 g), T = 30 ºC: 1 – 0.5 MPa; 2 – 1.0 MPa; 3 – 1.5 MPa; 4 -2.0 MPa; 5-2.5 MPa

The data in fig.40 confirm the literature data that even with a very small amount, the catalyst based on platinum group metals is effective in the hydrogenation of aromatic nitro compounds [22, 113]: at a pressure of 2.5 MPa (curve 5), the theoretically calculated amount of hydrogen is absorbed by the achievement of 26 minutes of a process and using only 0.02 g of catalyst. The course of the kinetic curves shows that the mechanism of the process does not depend on the applied hydrogen pressure. It is revealed that, irrespective of the catalyst and conditions of process, at the hydrogenation of p-NA and p-NP there is an absorption of the amount of hydrogen which is theoretically calculated on reaction. Whereas at hydrogenation of o-NP with pressure below 4.04.5 MPa there is an absorption of hydrogen in amount below than is required on reaction. With pressure over 4.0-4.5 MPa reduction of oNP proceeds up to the end. Order of reaction on hydrogen both for NP and p-NA is equal to 1. The results of hydrogenation of p-NA in ethanol at different temperatures and pressures on the Pd-Pt/γ-Al2O3 catalyst showed that at hydrogen pressures in the range 0.5-2.5 MPa, the reaction order for hydrogen is 1 (according to the bilogarithmic dependence of velocity 144

on pressure). Increasing the temperature from 25 to 60°C increases the rate of hydrogenation of p-NA. The apparent energy of activation of the process is 40.8 kJ/mol. The order of reaction on hydrogen calculated on dependence of lgW on lg (p·10) for NB by the time of absorption 1 mole of hydrogen and on initial velocities irrespective of the used catalyst, is equal 0.7 that indicates participation of atomic hydrogen in the course of reduction of nitrogroup. The effect of the amount of hydrogenated compound on the rate and selectivity of the process at a hydrogen pressure of 1.5 MPa and 30oC on all synthesized catalysts (0.04g) was studied. It was found that the shape of the kinetic curves with increasing the sample of NP and p-NA does not change. The reaction order for the substrate for NP is zero, for NA – the first. At the same time, a change in the order of the reaction from the substrate from -1 to +1 is typical for the reduction of the NB, which agrees well with the data in [149]. Table 15 – Reduction of p-, o-NP at hydrogen pressures of 0.5 and 2.0 MPa in isopropanol at different temperatures of the experiment. Catalyst: Pd/C, Pd/γ-Al2O3, catalyst amount-0.05 g, theoretically calculated amount of hydrogen-600 cm3

Catalyst

NP, isomer

Pd/C Pd/γ-Al2O3 Pd/C Pd/γ-Al2O3 Pd/C Pd/γ-Al2O3 Pd/C Pd/γ-Al2O3 Pd/C Pd/γ-Al2O3 Pd/C Pd/γ-Al2O3 Pd/C Pd/γ-Al2O3

oooooopppppppp-

Hydrogen W1MH2, Yield of Temperatu Duration, Pressure, mmol/min aminophen re, ºC min. MPa ol, % 30 0.5 30.0 22.5 68.0 50 0.5 36.0 19.0 71.0 50 0.5 50.0 20.0 92.0 50 0.5 85.0 18.0 98.0 80 0.5 200.0 24.0 86.0 80 0.5 218.8 20.0 90.0 30 0.5 59.0 24.0 90.0 30 0.5 65.0 22.0 94.0 50 2.0 140 22.0 90.0 50 2.0 152 20.0 95.0 60 0.5 180 19.8 92.0 60 0.5 220 17.5 97.0 70 2.0 215 14.0 90.0 70 2.0 240 10.0 99.0

145

The temperature dependence of the hydrogenation of the NP is described by the Arrhenius equation. The influence of the process temperature was studied at hydrogen pressures of 0.5 MPa and 2.0 MPa. In tab.15, in fig.41 data on the hydrogenation of NP at various temperatures of the experiment are given.

Figure 41 – Reduction of o-NP at different temperatures on Pd/C (0.02 g) and a hydrogen pressure of 0.5 MPa: 1-20ºC, 2- 60ºC, 3-40ºC, 4- 30ºC

The obtained data show that the speed of hydrogenation and the yield of aminophenol is lower in case of reduction of o-NP. At the same time temperature increase to 80ºC at hydrogenation of this compound was inexpedient – so, for example, for catalyst Pd/C at 0,5 MPa the yield of o-aminophenol decreased from 92.0% at 50ºC to 86.0% at 80ºC, the same tendency is noticed also for catalyst Pd/γAl2O3 – decrease of the yield of aminophenol was from 98.0 to 90.0%, respectively. As the reaction temperature increases from 60ºC to 80ºC, the process becomes complicated by side reactions. It was found that the hydrogenation of NP on Pd/γ-Al2O3 catalyst proceeds with better yields and a higher rate. The highest results on the synthesis of paminophenol were observed at 70ºC. The yield of p-aminophenol on the catalyst Pd/γ-Al2O3 at 2.0 MPa was 99%. 146

Experiments on the effect of temperature show that the optimal temperatures for hydrogenation of NP are 50ºC – for o-NP and 70ºC – for p-NP. It was found that hydrogenation in iso-propanol at 20-30ºC on catalysts deposited on coal, in addition to mixed Pd-Pt catalysts, in addition to AP, aminocyclohexanol (ACHOL) is formed, up to 6-8%. As the temperature rises above 30ºC, the hydrogenation rate of the benzene ring increases, and the yield of the corresponding ACHOL increases to 15-20%. The authors noted that hydrogenation of the aromatic ring was not observed for copper-modified palladium catalysts deposited on both types of carriers, as well as for Pd/γ-Al2O3. The presence ACHOL in catalyzate is confirmed by GLC and IR. The appearance of the OH group in the molecule of the aromatic nitro compound in p-position and, especially, in the o-position, decreases the adsorption of the nitro compound on the surface of the catalyst. Due to this, the ratio of reaction components (hydrogen and nitro compound) is violated on the catalyst surface, the reaction rate and the yield of the aminophenol decrease. The relatively low rate of o-NP reduction appears to be due to the appearance of the ortho-effect [150]. Ortho-effect is the aggregate of all kinds of spatial and stereoelectronic interactions of closely located substituents and the reaction center of the molecule. The substituent creates spatial obstacles that interfere with the approach of the reagent to the reaction center and its solvation in the solvent. There is a stereoelectronic retardation of the reaction due to a violation of coplanarity with the aromatic nucleus, a substituent or a reaction group in the o-disposition. Ortho substituents are close enough to the reaction center, so that a significant vicinal effect can occur. During hydrogenation of p-NA (interval-0.5-3.0 MPa), the apparent activation energy calculated from the Arrhenius equation and from the lgk dependence of 1/T (temperature range-20-70°C) is 35.0 kJ/mol. To determine the reason for the decrease in the rate of hydrogenation during the reaction, the effect of the reaction product, p-aminophenol (p-AP), introduced into the reaction environment in an equivalent amount, was studied [93, 94, 146]. Addition of the reaction product reduces the reduction rate and the amount of absorbed hydrogen (tab.16). This is due to the blocking of the catalyst surface by the reaction product – p-AP. 147

The ratio b1/b2 indicates a stronger adsorption of p-AP as compared to p-NP. p-NP has less access to the surface of the catalyst, since the surface of the catalyst is already occupied in the first seconds of the reaction by molecules of p-AP, which are readily adsorbed on the surface of the catalyst. The rate of the hydrogenation reaction of p-NP sharply decreases in the presence of p-AP, because the surface of the catalyst is poisoned by the reaction product. Calculation of the rate constants taking into account the adsorption coefficients shows that the reaction rate is constant, which confirms the assumption of a zero order of reduction of p-NP over the substrate. Table 16 – Reduction of p-NP and p-NP (based on 400 cm3 of hydrogen) in a mixture with p-AP in an equivalent amount at 0.5 MPa, T = 60°C. Catalyst – Pd-Cu/ γ-Al2O3 (0.05 g)

# 1 2 3 4 5

The volume of hydrogen absorbed from a gas phase, cm3 100 150 180 250 300

W, cm3/min. p-NP

p-NP+p-AP

85.0 72.0 65.0 56.0 34.0

20.0 16.0 13.5 12.0 7.7

The ratio of adsorption coefficients, b1/b2 0.23 0.22 0.21 0.21 0.22

The data obtained in the work allow one to assume a mechanism for the reduction of the investigated nitro compounds. In the hydrogenation of o- and p-NP, presumably, the corresponding hydroxylamine derivative is formed first, which instantaneously regroups into quinoneimine. For this reason, this particle is difficult to detect by gas-liquid chromatography. Then the quinoid group is fairly easily rearranged into the corresponding aminophenol. This reaction proceeds much more easily than the conversion of the NO2 group to the NH2 group. The reduction of p-nitroaniline proceeds according to the following scheme [93, 94, 146]: 2Н2 p-NA

2Н2 p-aminohydroxylamine

К1 =0.06

p-PhDA (15) К2 =0.17

148

10.5. Hydrogenation of nitro compounds on catalysts based on palladium-, platinum-containing carbon nanomaterials A study of the catalytic properties of Pt/NB and Pd/ND (NDnanodiamonds) in the hydrogenation of NB showed that the catalysts have high activity and stability (fig. 42), as well as selectivity: aniline is the only reaction product (no by-products formed, which was confirmed analysis of reaction mixtures by gas chromatography) [151154]. In this reaction, palladium-containing NA proved to be more effective than platinum-containing analogs. The most active catalyst in this reaction was 6% Pd/NA, while in all cases the effect of "development" of the catalysts is observed when adding a subsequent portion of nitrobenzene without separating the reaction products and the catalyst. Graphene is a two-dimensional material whose sp2-hybridized carbon atoms form a hexagonal lattice with a C-C bond length of 0.142 nm [155]. Due to its unique properties, graphene is used in the creation of transparent electrodes, photodetectors, chemical sensors, etc. Having a high specific surface area of 800-900 m2/g (fig.43), it can also be used to create new catalysts for organic synthesis reactions [156]. The main methods of obtaining graphene are presented in the reviews [157-159]. In addition to graphene itself, graphene oxide and reduced graphene oxide (RGO) are of practical interest, in the first place, by the presence of functional groups on their surface, the introduction and modification of which allows to improve the properties of graphene and expand the field of its application. In recent years, experience has accumulated on the creation on the surface of graphene materials of various functional groups, with the help of which it is possible to fix nanoparticles of metals and their oxides. Metal-containing graphene materials proved to be catalytically active, stable and selective in hydrogenation reactions. However, the effects of conjugation effect in the carrier and its 2D nature on the catalyzed reactions remain open. In this connection, it is of interest to obtain Pd-containing catalysts based on nanodiamonds and amine-functionalized graphite oxide and to study their catalytic properties in model hydrogenation reactions of 149

compounds with different chemical bonds (nitro group,> C = C C = N- bonds) and also to compare the obtained characteristics with the catalyst on activated carbon prepared by a similar procedure. This will make it possible to advance in solving one of the urgent problems of modern chemistry-the creation of new efficient catalysts for organic synthesis reactions. A number of papers have studied the catalytic properties of synthesized metal-containing graphene materials in various practically significant reactions: the hydrogenation of various nitro compounds to the corresponding amines [160-172]. The hydrogenation of nitrobenzene is one of the most common model reactions for studying the activity of samples of potential catalysts. In [166], the Pt/TiO2/RGO catalyst in the hydrogenation of nitrobenzene without a solvent showed high selectivity and activity (TOF = 59,000 h-1) as compared to Pt/TiO2 and Pt/RGO in 2.6 and 1.7 times, respectively. In addition, the catalyst can be reused for six times without loss of activity. Based on this, the authors conclude that the catalyst structure is stable. In comparison, Pt/TiO2 catalytic activity decreases by about 40% already in the second cycle, but Pt/RGO retains good catalytic activity after three cycles of use in hydrogenation.

Figure 42 – Velocity of hydrogenation reaction of nitrobenzene [151]

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Figure 43 – The ideal crystal structure of graphene, which is a hexagonal crystal lattice.

The photocatalytic activity of Ag/RGO has been studied in the reduction of nitrobenzene under visible light irradiation. A 100% conversion of nitrobenzene after irradiation is observed for 240 min. The catalyst remains stable after five cycles of nitrobenzene reduction without changes in the crystalline phase, composition, and absorption properties [162]. It was shown in [160] that at the hydrogenation of nitrobenzene, Pt/RGO was more active than Pt/CNM (CNM-carbon nanomaterials) and Pt/C in 12.5 and 19.5 times, respectively, at 0°C and 8 and 11.5 times, respectively, at 20°C. At the hydrogenation of substituted nitroarenes (o-, m-, pchloronitrobenzene, o-nitrotoluene, m-, p-nitrophenol, p-nitroaniline) over Pt/RGO were obtained the corresponding amines with high yields (94.3-98.9%) at 100% conversion of substrates (reaction conditions: 48.9 mM substrate, 40°C, 1.0 MPa, duration – 2 hours). The catalytic properties of Ru/RGO have been studied in the hydrogenation of p-chloronitrobenzene (p-CHNB) and a number of nitroarenes (o-, m-chloronitrobenzene, nitrobenzene, p-nitrotoluene, p-nitrophenol, p-nitromethoxybenzene) [164]. The catalyst was selective, the yields of the target products – aromatic amines were 96.0-99.4%. The stability of Ru /RGO is maintained unchanged for three consecutive cycles; in the fourth and fifth cycles, the selectivity 151

to p-chloroaniline is reduced from 96.0% to 92.0%. Based on the results of TEM after five cycles of hydrogenation, aggregation of Ru nanoparticles is noted, which, apparently, led to a decrease in the selectivity of Ru/RGO. In [173], catalysts prepared by the combined reduction of Pt (IV) and graphite oxide were studied in the hydrogenation reaction of nitrobenzene (45°C, 1 atm H2). It is shown that from four reducing agents (formate ion, ethylene glycol, sodium tetrahydroborate and hydrazine hydrate), only NaBH4 and hydrazine hydrate are suitable for the preparation of catalysts. The authors made the assumption that the particles Pt (>2 nm) are fixed on the defects, vacancies and functional groups formed as a result of the reduction. Pd/ND samples (1 wt%, 3 wt%, 6 wt%, 9 wt%, 10 wt%, 12 wt%, 15 wt%) were studied in [154]. The total specific surface area (SO) of the samples obtained ranges from 263 to 311 m2 / g, and the surface area of the catalytic metal is from 50 to 165 m2/g with particle sizes of the fixed metal of 3-5 nm. Catalytic activity was studied in the model hydrogenation reaction of nitrobenzene. At the hydrogenation of nitrobenzene with increasing metal content in Pd/ND catalysts with 1 wt.% to 3 wt.% reaction rate (W) increased 3.5 times. With a further increase in the palladium content for every 3 wt. % the rate of hydrogenation of nitrobenzene increases by 1.4-1.1 times. As the content of palladium increases, the activity of the catalysts decreases, thereby indicating the inefficiency of using samples with a high metal content. A study of the influence of the activation time of the catalyst (by the example of 9 wt% Pd/ND and 15 wt% Pd/ND) on the rate of the hydrogenation reaction of nitrobenzene and the activity of the catalyst showed that with increasing activation time, the rate and the TOF are increased, that is explained by formation of larger amount of Pd0. This assumption was confirmed by XPS analysis of the Pd/ND catalyst with a metal content of 10 wt. % and a specific surface area of 267 m2/g. Three samples were analyzed: a) initial; b) after its activation by hydrogen for 1 hour; c) after carrying out the hydrogenation reaction of the model substrate – nitrobenzene. In the C1s spectrum of all three samples a peak is observed at a binding energy of 285.18 eV, which consists of two components: a diamond phase with sp3-hybridization of carbon [174] and a graphite phase in 152

sp2-hybridization of the valence electronic states of the carbon atom, characteristic of activated carbon ( 284.7 eV) [175]. In the O1s spectrum (Esb = 531.14 eV), oxygen was detected in the carboxyl and carbonyl forms, as well as in the oxide form corresponding to the binding energy of PdO (529.3 eV). Chlorine is not found in any of the three samples. The presence of palladium in two valence states is established: Pd2+ and Pd0 in the ratio 1.06:1. After the reduction of the catalyst by hydrogen for one hour, the presence of both forms is maintained, with the ratio Pd2+:Pd0 shifting towards zero-valent palladium (1:1.23). In the sample, only Pd0 was detected after the hydrogenation reaction. At the same time, the catalyst is operative. It can be used many times without visible loss of activity. In the hydrogenation of the second portion of each substrate, the reaction rate was slightly higher than in the hydrogenation of the first portion, and then, with the addition of the next portion of the substrate, the reaction rate remained approximately the same, indicating the stability of the catalytic properties of the Pd/ND samples under study. The effect of "development" of the catalyst is more pronounced when using a sample that has been activated for 10 minutes. When hydrogenating nitrobenzene beginning with the third portion of the substrate, the reaction rate was practically constant. Activation parameters confirm that under the studied conditions hydrogenation of nitrobenzene on ND containing palladium proceeds in the kinetic region. The activation energy, like the activation entropy, is somewhat lower than for 1 wt. % Pd/C, which may indicate a more ordered structure of active metal centers, for example, for 3 wt. % Pd/ND. Physicochemical analyzes of carriers (ND, activated carbon of M200 grade) and catalysts based on them (1 wt% Pd/Nd, 1 wt% Pd/C) by SEM, energy dispersive X-ray spectroscopy (EDX) were carried out in [154] , as well as the XPS. The structure of the used carriers was used by the SEM method: M20 activated carbon (fig.44a) and ND (fig.44b). In fig. 43b it is visible that the structure of ND represents fractal system with various size of separate grains whereas the structure of activated carbon (fig.44a) consists of separate graphite flakes of various forms and the sizes.

153

a

b Figure 44 – SEM image of activated carbon M200 (a) and ND (b)

Using the EDX-analysis, a qualitative and quantitative study of the carrier surface was carried out. Both carriers have a carbon structure with the presence of oxygen-containing groups of various nature on the surface. The C:O ratio in both samples is approximately the same: 1:0.19. In the activated carbon sample, a potassium admixture of about 154

0.5 wt. % and other chemical elements, the presence of which is due to the nature of the source of activated carbon (M200 grade coal is made from coconut waste: coconut shells, wood). The main impurity in ND is iron, because they are synthesized in a steel chamber by the explosion of a mixture of TNT and hexogen with a negative oxygen balance [176]. In the overview of the XPS spectrum of the catalyst, 1 wt. % Pd/C1, lines of carbon, oxygen, palladium and chlorine are observed. In the sample, after the hydrogenation of nitrobenzene (Pd / C-2), a sodium line is added, apparently remaining after the activation of the NaBH4 catalyst. Observed C 1s-spectra of the test samples 1 wt. % Pd/C are typical for sp2-carbon and represent an intense asymmetrical line, characteristic for activated carbon with a binding energy of 284.5 eV [174-176]. Figure 45 shows the spectra of 3d-electrons of palladium for the initial catalyst and the catalyst after hydrogenation. It can be seen that the intensity of the palladium peaks decreases during hydrogenation. The reasons for this can be both the enlargement of the palladium particles during the hydrogenation process and their partial removal by the reaction mixture. The choice between these options can be made by comparing the obtained data with the results of elemental analysis. Indeed, in the case of Pd/C, the palladium content in the catalyst decreased almost twofold after the reaction. When the spectrum is decomposed into components (one example of the decomposition is shown in fig.45), a component with an intensity of several percent and a binding energy of more than 338 eV, which can be attributed to Pd2+ ions, always appears. It is not yet possible to answer the question of the nature of this component unambiguously. However, most likely, its origin can be related either to palladium oxide or to [PdCl4]2- ions, which are fixed in places inaccessible to the reductant. The latter variant is supported by the fact that the catalyst contains chlorine both before and after the reaction. Comparing the results of the analysis of catalysts, it can be stated that palladium fixed to ND does not wash off during the reaction from the carrier, whereas, in the case of Pd/C, metal losses amounted to almost 50% of the initial content. This may be the result of the participation of nitrogen-containing groups of ND (amino or amide) 155

[177] in the process of palladium fixation. Indeed, in the XPS spectra before and after the reaction in the presence of Pd/ND the presence of nitrogen is fixed, while the Pd/C is not. In Pd/C part of the metal (79%) is in places inaccessible to the reductant and therefore remains inactive. After the reaction in both catalysts, the main peaks shift both Pd3d5/2 and Pd3d3/2 towards higher binding energies, apparently due to partial oxidation of the metal centers by formation of surface complexes with charge transfer from palladium to nitrobenzene. In addition, the nature of the carrier affects the binding energy of the palladium electrons. In the case of ND, this value at Pd3d5/2 level is 335.0 eV, whereas for coal it is 335.3 eV.

Figure 45 – Pd 3d-photoelectron spectra of 1 wt. % Pd/C before the reaction Pd/C-1 and after hydrogenation of nitrobenzene Pd/C-2, respectively

Properties 1 wt. % Pd/ND and 1 wt. % Pd/C were studied in the hydrogenation reactions of nitrobenzene and its para-substituted analogues (p-nitroaniline, p-nitrophenol, p-nitrobenzoic acid), as well as cyclohexene, hexene-1, allyl alcohol, acrylic, methacrylic, crotonic and cinnamic acids (fig.46). The proposed substrates differ in the nature and location of the groups being reduced, which makes it possible under comparable conditions to trace the influence of the nature of the catalyst on the 156

kinetic parameters of hydrogenation, and also to study the effect of the substituent in nitroarenes on the rate of reduction of the NO2 group. The choice of substrates was due not only to their practical importance, but also to the interest in studying the mechanisms of the reduction of functional groups (NO2-,> C = C pnitrobenzoic acid almost 2-fold. This fact can be explained by the presence of fixed metal clusters of various nature and geometry on the surface of activated carbon. The effect of the donor substituent on the para-position does not significantly affect the rate constant of hydrogenation of the nitro group, however, the introduction of the acceptor substituent (carboxyl group) reduces it almost twice. The explanation of the observed effect can be that the substituents in the benzene ring are in the para position with respect to the nitro group, their electronic influence on each other is less than the effect of the steric effect of the substituents on the interaction of the substrate with the catalytic center. The author concluded that the catalyst based on activated carbon is 1.5-2.8 times less sensitive to a change in the nature of the substrate than 1 wt. % Pd/ND. For the catalyst supported on activated carbon, only the nature of the substituent affects the reaction constant. For example, pnitrobenzoic acid has a rate constant of 1.5 lower than for nitrobenzene or its para-substituted compounds with donor substituents. This fact suggests that, depending on the nature of the substrate to these catalysts, nitro limiting stage reduction process may be different. The nature of the substituent can influence the mechanism of reduction, and the size of the substituent imposes steric restrictions when the molecule approaches the catalytic center. A new method for the reduction of organic compounds containing a nitro group, C = C, C = N-, and C-Hal bonds was developed in [154], consisting of hydrogenation with molecular hydrogen in the presence of palladium-containing graphite oxide, functionalized with ethylenediamine (EA), diethylenetriamine DA) and triethylenetetramine (TA). It was found that the rate of the hydrogenation reaction increases in the series EA Rh-Pd>>Pd-Ru>Rh (fig.77). Bimetallic catalysts are more active and selective than monometallic. The maximum values of benzene and toluene conversion (85.0-93.0%) and yield of the corresponding hydrogenation products of the aromatic ring were found on the bimetallic catalysts Pd-Pt/Al2O3 and Rh-Pt/Al2O3. Catalysts supported on alumina were more active and selective than the catalysts supported on silica. It was found that the reaction rate decreases with increasing complexity of the structure of compounds in the series: benzene>>ethylbenzene>cumene. These data are consistent with the data in [19-22, 47, 49], where the rate of hydrogenation of benzene is higher than the rate of its homologues hydrogenation. This is probably due to the presence of unsaturated side chains in aromatic hydrocarbons. GLC analysis and IR spectroscopy data showed the high yields of the desired products (up to 98-99%). Hydrogenation of aromatic hydrocarbons on Pd-Pt- catalysts on various carriers was also carried out. On catalysts supported on zeolites, in the reaction products the cracking products were also present in minor amounts (to 5.0%). There is a partial reduction of benzene to cyclohexene (10-18%) on Ru catalysts, the yield of cyclohexane – not higher than 30-46%. Optimum catalysts for the hydrogenation of benzene and toluene – the catalysts with ratio Pt:Pd = 3-7; 2-8; 1-9. Microdiffraction patterns of catalyst with Pd/Al2O3 composition corresponds to metallic Pd, moreover, there are in a small amount (45%) the particles of PdO. X-ray phase analysis of the catalyst of composition Pd/Al2O3 showed the presence of the metallic phase Pd peak – ICDD No.87-0653, d = 2.25, 1.95, 1.38, and phase γ-Al2O3 (2u = 458 d -1.99, 2u = 36.18 d-2.46) [59]. It was revealed the formation of solid solutions and the presence of traces of free Pd for systems PdPt-catalyst. X-ray analysis of the reduced mixed Pd-Pt-catalysts showed that palladium indicated distinct midline intensity on the diffraction patterns; parameter of lattice didn't differ from the known in the literature. There are lines of Pd and unreduced oxide PdO on the 248

diffractogramm, and its amount is close to 10%. The results of temperature-programmed reduction (TPR) show, that all Pdcontaining catalysts possibly contain palladium in at least in two forms: PdO particles and Pd oxide species stabilized on a surface.

Figure 77 – The hydrogenation of benzene in an autoclave without solvent at different catalysts supported on Al2O3, PH2=2.5 MPa, T=120°C: 1-Rh, 2-Rh-Pd(1:1), 3-Rh-Pd(9:1), 4-Rh-Pt.

For studying the behavior of NP and benzene at hydrogenation in the liquid phase at hydrogen pressure supported catalysts based on Pd and Pt with builder – Cu were synthesized. In the preparation of catalysts as the carriers were used γ-Al2O3 and activated carbon (C). As a result of physico-chemical studies of catalysts it was found that catalysts supported on a surface area C is almost 2 times greater than the surface of catalysts supported on γ-Al2O3. Pores of catalysts with γ-Al2O3 carrier have the shape of cylinders, which radius are within the range 20-22 Å. According to XPS, palladium on C is fully reduced to the zero-valent state, whereas γ-Al2O3, palladium is not fully reduced. Electron binding energy Pd0 3d5/2 Pd/C is 336.5 eV, corresponding to Pd2+. Modification of the catalyst with copper ions does not change the binding energy of the electron Pd 3d5/2. By XRPmethod was revealed that in the copper-modified catalysts based on 249

Pd (Pd-Cu) – Pd is in the zero valence state, and the state of copper Cu is characterized by the binding energy of 2p3/2 electrons, equals to 932.7 eV, corresponding to Cu+, so it's possible to suggest that Cu catalysts are in the form of Cu2O. It is found that in addition to the zero valent Pd, there is also oxidized form of palladium (PdO2) on the surface. Results testing of catalyst by method hydrogen TPD show that for supported bimetallic catalysts number of forms of the sorbed hydrogen, characteristic for each of the components remains constant, while the ratio between the hydrogen forms vary considerably with the change of the catalyst composition (fig.78). Hydrogen from Pd-Ptcatalysts put on γ-Al2O3 is desorbed in the form of dissolved and strongly adsorbed. If use addition of Pd and Pt in composition of the Rh-catalyst there is a shift of position of peaks of a desorption of hydrogen and change in a ratio of a share of this or that form of hydrogen. Probably, the high selectivity of 0.5% Rh-Pt (9:1)/A12O3 is associated with the presence of a large share of hydrogen with an average energy bond with the surface. A mixed Pt-Pd catalyst has a higher adsorption capacity to hydrogen than platinum and palladium separately.

Figure 78 – Thermodesorption of hydrogen from various catalysts with a linear increase in temperature within 0-750ºC: 1–Rh/А12O3; 2-Рd/А12O3; 3–Rh-Рd(1:1)/А12O3; 4–Rh-Рt (1:1)/А12O3; 5- Rh-Рd(9:1)/А12O3; 6-Rh-Рt(9:1)/А12O3; 7–Рd-Ru(1:1)/А12O3

250

Graphene materials containing platinum and palladium exhibit catalytic activity in hydrogenation reactions of compounds with multiple double [60, 61] and triple bonds [62, 63]. In the work [64] the composite obtained from graphite oxide, ionic liquid (IL) and Ru: Ru / graphite-IL oxide (1.61 wt% Ru) was successfully used as a catalyst in the hydrogenation of benzene to cyclohexane: the yield of the product was 99.9%. The high activity of Ru / graphite oxide-IL is retained even after several cycles of use in hydrogenation. A similar reaction with toluene was slower than with benzene, methylcyclohexane was formed in a yield of 90% after 24 hours. The styrene on Ru/graphite oxide-IL was hydrogenated to form two products: ethylcyclohexane (72% yield) and ethylbenzene (yield 27%), and 1,3-cyclohexadiene to cyclohexane (26%) and cyclohexene (68%).

Chapter 17. Hydrogenation of polynuclear aromatic hydrocarbons Polynuclear aromatic hydrocarbons (PAHs) can be considered as analogues of high-boiling fractions of oil and residues, fragments of the organic mass of coal, and the primary coal tar and its fraction comprising aromatic structures whose relative proportion and structural features depend on the degree of metamorphism of the coals. PAHs are also intermediates in the distribution of hydrogen in coal material under the influence of temperature and chemical reagents. It should be noted that the information on the behavior of individual PAHs in catalytic hydrogenation is very sketchy and very often contradictory, and data on their physicochemical properties are practically absent. Meanwhile, they play an essential role as components of the paste generator in hydrogen transfer reactions, affect the parameters of the processes of liquefaction of coal and primary coal tar [65-67]. Since hydrocarbon raw materials (coal, peat, shale, heavy oil, coal tar, etc.) is a complex mixture of organic and mineral substances, it is difficult to investigate. To model the activity and selectivity of selected catalysts, model compounds (anthracene, phenanthrene, pyrene, naphthalene, etc.) are often used, since the study of the 251

dependence of reactivity on the chemical structure of substances is possible due to model organic compounds that can fragmentarily represent the behavior of organic mass of raw materials. In addition, model compounds in the temperature range of destructive hydrogenation are not degraded [68]. Polynuclear aromatic compounds can be divided into two main types [69]: 1. Compounds in which the benzene nuclei are isolated and to some extent autonomous: diphenyl (fig.79), fluorine (fig.80), diphenylmethane (fig.81), triphenylmethane (fig.82). 2. Compounds with condensed benzene nuclei: naphthalene (fig.83), anthracene (fig.84), phenanthrene (fig.85).

Figure 79 – Diphenyl

Figure 80 – Fluorene

Figure 81 – Diphenylmethane

252

Figure 82 – Triphenylmethane

Figure 83 – Naphthalene

Figure 84 – Anthracene

Figure 85 – Phenanthrene

The work [70] shows that the hydrogenation of polyaromatic hydrocarbons proceeds through a series of successive stages. For example, naphthalene is hydrogenated to the decahydroproduct via the 253

formation of tetrahydronaphthalene. Over industrial sulphide catalysts, naphthalene can be almost completely hydrogenated at a pressure of 10-15 MPa and a temperature of 360-380 ° C. When the process temperature drops to 250 – 280°C, the pressure must be raised to 30 MPa. For comparison, deep hydrogenation of naphthalene over an aluminoplatinum catalyst is achieved at a pressure of 0.9-2.5 MPa and a temperature of 320-350°C. The probability of the formation of incomplete or complete hydroderivatives of naphthalene is determined by the conditions of the process. The formation of tetralin is promoted by elevated temperatures and low pressures. Elevated pressures increase the yield of decaline. The condensation of two or more benzene rings disrupts their symmetry and the equality of the electron density of bonds, so that in condensed aromatic hydrocarbons some bonds are shortened and have a multiplicity greater than in benzene, i.e. to a greater extent, approaching by unsaturation to a double bond: naphthalene – 1,725; anthracene – 1.738; phenanthrene – 1.776; chrysene – 1,754; 1,2benzoanthracene – 1.783 [71, 72]. To a lesser extent, this refers to centered hydrocarbons. Thus, pyrene (fig.86) has 6 bonds of 0.139 nm length, coronene (fig.87) – 6 bonds of 0.1385 nm length, i.e. which differ little from 6 bonds in benzene, having a length of 0.140 nm [73].

Figure 86 – Pyrene

Figure 87 – Coronene

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These data show that polycondensed aromatics have sufficiently reactive bonds having partially isolated double bond character. However, in quantitative terms, they are far from olefins and cycloolefins. Thus, in the hydrogenation of model compounds on NiAl2O3, naphthalene was hydrogenated more rapidly than benzene 3 times, cyclohexene 150 times, cyclopentene 294-470 times, α-hexene 306 times, and styrene 900 times. Even a sterically hindered 1-methylcyclohexene-1 was hydrogenated 5.1 times faster than benzene. The quantitative difference that turns into a qualitative difference, the hydrogenation of olefins and aromatic compounds is confirmed by calculations of the enthalpies of numerous hydrogenation reactions: in the case of olefins, they range from -23.8 to -32.8, and for aromatic compounds from -13.5 to – 16.7 kcal/mol [74]. Despite the fact that with each catalyst, a number of compounds are formed according to reactivity, some trends can be identified. First, the higher reactivity of polyaromatic hydrocarbons in comparison with monocyclic hydrocarbons. This difference is particularly pronounced in experiments with high-temperature, i.e. relatively less active catalysts. From low-temperature catalysts, experiments with a platinum catalyst are excluded from this pattern [75-78]. The monograph explains this anomaly on the basis of the principle of geometric correspondence of the multiplet theory of catalysis of A.A. Balandin. When hydrogenated on a platinum catalyst, the hydrocarbons are adsorbed by the plane, but the hydrocarbon bonds must be aligned with the active centers of the catalyst so that one of them activates the bond itself, and the nearest hydrogen molecule (the so-called sextet model for the case of benzene [8]. A comparison of the geometry of the surface of a platinum catalyst with the dimensions of hydrocarbon molecules shows that in the case of benzene 3 bonds from 6, diphenyl-4 bonds of 12 are activated, and in the cases of naphthalene, anthracene and 2,3-benzanthracene, only 2 of 4 truncated bonds are activated. Angular and centered hydrocarbons, adsorption options are possible when none of the bonds are activated. As for phenanthrene and 1,2-benzanthracene, the truncated bond is activated only in one of two possible adsorption positions; in the case of pyrene and coronene, only one of the six truncated bonds is activated. 255

Therefore, from the experiments with the platinum catalyst, only the experimental data can be compared, when the hydrocarbons were similar in structure and, consequently, adsorbed on the catalyst surface. Then, in such series, the hydrogenation rate is sympathetic with the order of the most unsaturated bond (fig. 88). In most experiments, phenanthrene is hydrated more slowly than anthracene, although the order of the truncated bond is greater in it than in anthracene. Obviously, one should take into account the number of shortened bonds: one in phenanthrene with the order of 1.775, in anthracene – four, although with the order of 1.738.

Figure 88 – Hydrogenation rates of polyaromatic compounds

In a series of experiments with a catalyst, rib adsorption (a doublet mechanism) may have taken place, as a result of which phenanthrene is more easily hydrogenated than anthracene, – one bond was activated, and it is more unsaturated in phenanthrene. However, even the most reactive polycyclic aromatic hydrocarbons having very truncated bonds are inferior to olefins, as mentioned above, and as can be seen from the data of experiments with the reduced nickel catalyst. Thus, an important trend determining the rate of hydrogenation of aromatic hydrocarbons is its dependence on the presence of truncated bonds and their number if the process is not complicated by the features of the effect of catalysts. The most common are qualitative differences:

256

1. Polycyclic hydrocarbons are hydrogenated faster than monocyclic hydrocarbons; 2. Tricyclic aromatic compounds are hydrogenated more rapidly than bicyclic; 3. Among the hydrocarbons with 3 or more rings, the linear is more quickly hydrogenated, followed by the angular and centered ones. These differences correspond to data from studies in which hydrogenation of hydrocarbons, more complex in structure than benzene and naphthalene, was studied. When studying the conversion of mixtures of the partial hydrogenation products of phenanthrene and pyrene on a nickel catalyst with a zeolite carrier (pressure 10 MPa, temperature and space velocities varied), the phenanthrene hydrogenation product showed a residual content of 14.8%, in the pyrene hydrogenation product of pyrene itself did not remain, but at a volumetric rate of 2.2L-1, 7.02% pyrene formed due to partial dehydrogenation [79]. In comparable conditions at a temperature of 343-344°C and a rate of 1.09-1.12L-1, phenanthrene turned whole, and pyrene remained 2.41%. As for polycyclic hydrocarbons with 3-4 or more aromatic rings under high-temperature hydrogenation, the possibility of a thermodynamic restriction must be taken into account. For example, coronene was hydrogenated on platinum and nickel catalysts at 4050°C, albeit slowly, and on an iron catalyst at 480 ° C hydrogenation did not take place [80]. Calculations in [81] show that at a temperature of 497°C and a pressure of 30 MPa the equilibrium fraction of the hydro-derivative with one aromatic ring decreases from 86.5% for naphthalene (reaction of naphthalene → tetralin) to 13.7% for phenanthrene (phenanthrene → octahydrophenanthrene), perhydrocoronene dehydrated already at 408°C even at a pressure of 25 MPa. It should be noted that the rate of hydrogenation is greatly affected by the degree of saturation (fig. 89). For example, at each stage of hydrogenation of anthracene, more stringent conditions must be applied [82]. In other words, multi-ringed aromatic hydrocarbons are hydrogenated stepwise; the last ring is most difficult to hydrogenate, 257

and in such hydrocarbons as perylene and decacyclene it is not hydrogenated at all. From the data given in tab.23 shows that as the hydrogen saturation rings hydrogenation rate decreases, although differently under different conditions [83].

Figure 89 – Scheme of hydrogenation of anthracene

Table 23 – Relative rates of hydrogenation of aromatic hydrocarbons on low- and high-temperature catalysts [83] Reaction

Benzene → cyclohexane Naphthalene → tetralin Tetraline → decalin Anthracene → dihydroanthracene Dihydroanthracene → tetrahydroanthracene Tetrahydroanthracene → octahydroanthracene Octahydroanthracene → perhydroanthracene Chrisen → tetrahydrohrysen Tetrahydrochrisin → Octahydrochrisen Octahydrochrisen → dodecahydrochrisen

Relative hydrogenation rate NiO – Al2O3, MoS2, WS2, 120-200 ºC, 3420 ºC, 400 ºC, 5 MPa 20 MPa 15 MPa 100 100 100 314 1,409 2,300 24 287 250 326 6,210 308 1,380 147

-

460

4.4

-

299 80 75 95

258

On the platinum catalyst at a temperature of 40°C and a pressure of 0.25 MPa), the same pattern was observed (fig. 90) [84]:

Figure 90 – Speed of the reaction of hydrogenation of chrysene on a platinum catalyst (K·103, min-1).

The fact that the decrease in the rate of hydrogenation is determined by screening can be illustrated by comparing the rates of hydrogenation of benzene and naphthalene in "a pure form" and surrounded by rings (fig. 91) [69-84]:

Figure 91 – Rates of hydrogenation of benzene and naphthalene in "a pure form" and surrounded by rings (K·103, min-1).

In the work [85] the hydrogenation of aromatic hydrocarbons on complex organometallic catalysts proceeds through the formation of a π-complex between a hydrocarbon molecule and a transition metal atom followed by successive addition of hydrogen. Introduction and 259

accumulation of substituents reduced the rate of hydrogenation, but the change in activation energy was different. In conditions typical for the liquefaction of coal, mostly lowactivity catalysts are used, and sometimes processes are carried out without catalysts, due to which high temperatures up to 500 ° C are forced to be applied. Under these conditions, the bond cleavage reactions of the two aliphatic carbon atoms become just as likely as the hydrogenation of the aromatic ring. If the enthalpy of hydrogenation of aromatic rings varies from -3.5 to -16.7 kcal / mol, then the breakdown of the C-C bond is from -6.9 to -16.5 kcal / mol, i.e. some cracking reactions will be thermodynamically as beneficial as hydrogenation. The fact that the hydrogenation of polycyclic hydrocarbons is accompanied by degradation reactions has already been shown in the first works with the simplest polycyclic hydrocarbons, which were considered as models of coal matter. For example, Ipatiev and Orlov, in experiments with a Fe-clay catalyst at a pressure of 7 MPa and a temperature of 440-465°C, showed a rapid destruction of paraffinic hydrocarbons, dibenzyl (to toluene), while naphthalene and its homologues were converted in three ways [86]: 1. Demethylation (naphthalene from methyland dimethylnaphthalenes); 2. Hydrogenation (fractions giving the initial hydrocarbon after dehydrogenation); 3. Destruction (fractions of monocyclic aromatic hydrocarbons, oxidizing benzoic and phthalic acids). Numerous authors who studied the destructive hydrogenation of aromatic hydrocarbons came to the conclusion that the saturation and destruction of rings were accompanied by partial isomerization, the ruptures of naphthenic rings occur only in α-bonds [87, 88]. The explanation of the stepwise mechanism was given by Lozov and Senyavin on the basis of a comparison of the kinetic regularities [89]: while the rate of hydrogenation of the polycyclic hydrocarbon decreases as it saturates, the rate of splitting increases in the rows (fig. 92).

260

Figure 92 – Increase in the rate of cleavage

For this reason, hydrogenation of coals and coal resins under industrial conditions is dominated by hydroaromatic hydrocarbons with one and two naphthenic rings. Kalechits I.V., studying the group composition of hydrogenated semi-coke resin, coal and a two-component model mixture, divided aromatic hydrocarbons into types by ring analysis of narrow fractions. The result of the conclusions about successive transformations were the schemes (fig. 93, 94), which are in many respects similar to the schemes of liquid-phase processes [67].

Figure 93 – Scheme of sequential transformation of a three-ringed aromatic hydrocarbon

Figure 94 – Diagram of sequential conversion of a four-ringed aromatic hydrocarbon

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These schemes have an illustrative value, since each type of hydrocarbon could be formed by the reduction of oxygen derivatives or heterocycles. However, they show well the predominance of hydroaromatic hydrocarbons with one naphthenic ring and a high probability of successive transformations, indicated by arrows. When comparing the reaction rates in [67] rapid hydrogenation of three-ringed hydrocarbons was observed, slightly more slowly – of two-ringed hydrocarbons and the accumulation of monocyclic hydrocarbons. The author established the regularity of reducing the rate of hydrogenation and increasing the rate of cleavage with increasing hydrocarbon saturation. Heterocyclic compounds are hydrogenated to the ring (fig. 95) containing a heteroatom, followed by a breakdown of the carbonheteroatom bond and the removal of the latter. The substituents on aromatic rings, as a rule, make hydrogenation more difficult [85-90].

Figure 95 – Scheme of hydrogenation of heterocyclic compounds

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Part VII. HYDROGENATION OF HYDROCARBONIC RAW  MATERIALS    The most important of the reactions that make up hydrogenation processes are hydrogenation and dehydrogenation, bound by a mobile equilibrium, the position of which is determined by such factors as hydrogen temperature and pressure [1]. In the fuel and processing industry, the hydrogenation of solid and heavy hydrocarbon raw materials (SHHRM) is used to produce motor fuel, lubricating oils and chemical products. Hydrogenation of the SHHRM is a universal alternative method for producing synthetic liquid fuel [2]. The development of research in the field of hydrogenation dates back to 1897-1900, when P. Sabatier (France) and N.D. Zelinsky (Russia) with their students developed the basics of hydrogenation catalysis of organic compounds [3-6]. In recent years, in all countries there has been an increasing tightening of the requirements for the quality of motor fuels and oils. In particular, this concerns the restrictions imposed on the content of aromatic hydrocarbons and sulfur compounds in them [4, 7]. When they burn into the exhausts of motor engines in large quantities fall into such harmful substances for health, such as carbon monoxide, sulfur dioxide, soot. In addition, many aromatic hydrocarbons are themselves highly toxic substances. In the standards adopted for gasoline, an increasing limitation is observed in the reduction of the maximum permissible total content of aromatic hydrocarbons, benzene, and also sulfur compounds. To produce diesel fuels, straight-run diesel fractions are used as raw materials, as well as secondary process fractions, such as light and heavy catalytic cracking gas oils, thermal cracking gas oils containing different amounts of aromatic compounds. Of these distillates, the greatest amount of aromatic compounds is contained in the light gas oil of catalytic cracking (54-70% by weight) [8, 9]. For the production of diesel fuels, diesel fractions obtained by direct distillation of oil, as well as fractions of secondary processes, such as light catalytic cracking gas oil, thermal cracking gas oil and others containing various amounts of aromatic compounds [4, 5]. 268

Most aromatic compounds contain light catalytic cracking gas oil, as well as thermal cracking gas oil. The qualitative composition of aromatic hydrocarbons of these distillates is diverse. For example, depending on the origin, monocyclic (heavy catalytic cracking gas oil, heavy atmospheric gas oil) or bicyclic (light coker gas oil) aromatic hydrocarbons may predominate in them [10].

Chapter 18. Processes examples The raw materials of the hydrotreating processes are gasoline, kerosene and diesel fractions, vacuum gas oil and lubricating oils containing sulfur, nitrogen and unsaturated hydrocarbons. The content of heteroatomic hydrocarbons in the feedstock varies very significantly, depending on the fractional and chemical composition of the distillates. As raw materials become heavier, not only the total content increases, but also the share of the most thermostable with respect to hydrogenolysis hetero-organic compounds increases. For each type of feedstock and catalyst, there is an optimal range of operating parameters. Although the hydrogenolysis reactions of the heteroorganic compounds are exothermic, the hydrofining processes of the fuel fractions are usually carried out in an adiabatic reactor without removing heat from the reactions, since the temperature gradient usually does not exceed 10ºC. In industrial hydrogenation plants, two methods of separating hydrogen-containing gas from hydrogen gas are used (fig.96): cold, low-temperature (a), and hot, high-temperature (b) [10-12]. Cold separation of HCG consists in cooling of the gas-product mixture leaving the hydrotreating reactors, at first in heat exchangers, then in refrigerators (air and water) and separating of HCG in a separator at a low temperature and high pressure. In a separator of low pressure separate the low-molecular hydrocarbonic gases. It is applied on hydrotreating installations of: - petrol fractions, - kerosene fractions, - sometimes diesel fractions.

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a

b Figure 96 – Cold (a) and hot (b) separation schemes for hydrogen containing gas (HCG): HCG – hydrogen containing gas, SHP-separators of high pressure, SLP – Separators of low pressure, CS – cold separators, HS – hot separators

At hot separation the gas-product mixture after partial cooling in heat exchangers is fed to a hot separator; HCG separated in it and hydrocarbonic gases are cooled up to the low temperature in air and water refrigerators and then they are sent to a cold separator where HCG with rather high concentration of hydrogen is selected [12, 13]. Hot separation of HCG is applied mainly on installations of hydrodesulphurization of the high-boiling fractions of oil: – diesel fuels, – vacuum gas oils, – oil distillates, – paraffins. Cold separation of HCG, compared to hot separation, provides a higher concentration of hydrogen in HCG. The main advantage of the hot separation option is a lower consumption of both heat and cold.

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18.1. Installation of hydrotreating of diesel fuel The circulating HCG (fig.97) is mixed with the feed, the mixture is heated in the raw heat exchangers and in the tube furnace F-1 to the reaction temperature and fed to the reactor R-1. After the reactor, the gas mixture is partly cooled in raw heat exchangers (to a temperature of 210-230°C) and sent to the HCG hot separation section consisting of separators S-1 and S-2. HCG, withdrawn from the cold separator S2 after purification with MEA absorber C-2 is fed to the circulation. The hydrogenates of the hot and cold separators are mixed and directed to a stabilization column C-1, whereby the hydrocarbon gases and the distillate (gasoline) are removed from the purified product by the circulating of the preheated into the furnace F-1 HCG [12, 14]. Table 24 shows data on the material balance of hydrotreater units for gasoline (I), kerosene (II), diesel fuel (III), and hydrodesulfurization of vacuum distillate, a feedstock of catalytic cracking (IV). Table 24 – Material balance of hydrotreating units No

1 2

1 2 3 4 5 6

Data of process

Raw materials Hydrogen 100% on the reaction * TOTAL

Raw materials I II III It is taken, %: 100.00 100.00 100.00 0.15 0.25 0.40

100,15 100,25 100,40 It is obtained,%: Hydrotreated fuel 99.00 97.90 96.90 Diesel fraction Distillation 1.10 1.3 Hydrocarbon gas 0.65 0.65 0.6 Hydrogen sulphide 0.2 1.2 Losses 0.5 0.4 0.4 TOTAL 100,15 100,25 100,40 * Total consumption taking into account dissolution losses.

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IV 100.00 0.65 100,65 86.75 9.2 1.3 1.5 1.5 0.4 100.65

Figure 97 – Principal technological scheme of the hydrotreating unit for diesel fuel: I – raw materials; II – fresh HCG; III – hydrogenate; IV – gasoline; V – hydrocarbon gas for cleaning; VI – blow-off HCG; VII – regenerated MEA; VIII – solution of MEA for regeneration

18.2. Hydrotreating of vacuum distillates Vacuum distillates are traditional raw materials for processes of catalytic cracking and hydrocracking. The quality of vacuum gas oils is determined by the depth of selection and the clarity of rectification of fuel oil. Vacuum gas oils 350-500°C practically do not contain organometallic compounds and asphaltenes, and their coking ability usually does not exceed 0.2%. The effect of metals contained in raw materials, nitrogenous compounds and sulfur is manifested in a decrease in the activity of the catalyst due to the deposition of coke and irreversible metal poisoning. Hydrotreatment of vacuum gas oil 350-500°C does not present significant difficulties and is carried out in conditions and equipment similar to those used for hydrotreating diesel fuels. At a pressure of 45 MPa, a temperature of 360-410°C and a feed speed of 1-1.5 h-1, the desulfurization depth is reached up to 89-94%; the nitrogen content is reduced by 20-30%, metals by 75-85%, and coking by 65-70% [15, 16]. The hydrotreatment of heavy distillates of destructive processes (coking, visbreaking) is usually carried out in a mixture of straight-run distillates in an amount up to 30%. 272

Hydrotreating of oil raffinates is used mainly for color clarification and improvement of their stability against oxidation; simultaneously reduces their coking ability and sulfur content (desulfurization depth is 30-40%); the viscosity index slightly increases (by 1-2 units); the pour point of the oil rises by 1-3°C. The yield of base oils of distillate and residual raffinates is more than 97% by wt. Installations for hydrotreating oils differ from the hydrotreating of diesel fuels only in the way of stabilizing hydrogenation: stripping of hydrocarbon gases and gasoline vapors is carried out by the supply of water vapor; then the stable oil is dried in a vacuum column at a pressure of 13.3 · 103 Pa. 18.3. Hydrotreating of oil residues In modern world oil refining, the most urgent and complex problem is refining (demetallization, deasphalting and desulfurization) and catalytic processing (catalytic cracking, hydrocracking) of oil residues – tar and fuel oil, the potential content of which in the oils of most fields is 20-55%. The most important quality indicators of oil residues as raw materials for catalytic processes, their refinement and processing are the content of metals (determining the degree of deactivation of the catalyst and its consumption) and coking ability (causing coking of catalytic cracking regenerators or hydrogen consumption in hydrogenation processes). These indicators were the basis for the classification of residual raw materials for catalytic cracking processes accepted abroad. The content of metals and coking in accordance with this classification of oil residues are divided into the following four groups (tab.25). Table 25 – Classification of oil residues Group I II III IV

Coking ability, % wt. Less than 5 5-10 10-20 More than 20

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The content of metals, g/ton Less than 10 10-30 30-150 More than 150

I. High-quality raw materials (for example, mazut of Mangyshlak or Grozny oil). It can be processed without preliminary preparation in installations of CCF (catalytic cracking fluid) of lift-reactor type with passivation of metals and heat removal in regenerators. II. Medium-quality raw materials. It can be processed in the CCF plants of the latest models with a two-stage regenerator and removal of excess heat without preliminary preparation, but with an increased consumption of a metal-resistant catalyst and passivation of the poisoning effect of raw metals. III and IV. Low quality raw material (e.g., fuel oils and asphalts of West-Siberian, Romashkinskoye, Arlanskoe oils). Catalytic processing requires obligatory preliminary preparation – demetallization and deasphalting [12, 16-18]. For the processing of fuel oil in low-sulfur boiler fuel, the following methods of “indirect” hydrodesulphurization were proposed and implemented: 1. Vacuum (or deep vacuum) distillation of fuel oil followed by hydrodesulfurization of vacuum (deep vacuum) gas oil and mixing of the latter with tar (sulfur content in boiler fuel 1.4-8%); 2. Vacuum distillation of fuel oil and deasphalting of tar, followed by desulfurization of vacuum gas oil and deasphalted oil and mixing them with deasphalting residue (sulfur content in boiler fuel 0.41.4%); 3. Vacuum distillation of fuel oil and deasphalting of tar, followed by hydrodesulfurization of vacuum gas oil and deasphaltizate and their mixing (the sulfur content in the boiler fuel is 0.2-0.3%), the deasphalting residue is subjected to gasification or separate processing to produce bitumen, pitch, binders, fuel coke, etc. Modern foreign industrial installations of hydrodesulfurization of oil residues can be divided into the following options: 1) Hydrodesulfurization in one multilayer reactor using the largeporous metal-intensive catalysts at the beginning of the process and then catalysts with high hydrodesulfurization activity; 2) Hydrodesulfurization in two and more step reactors with a stationary catalyst bed, of which the head (preliminary) reactor is designed for demetallization and deasphalting of raw materials on cheap metal-intensive (often not regenerated) catalysts, and the latter (or latter) for hydrodesulfurization of demetallized raw materials; 274

3) Hydrodesulfurization in a reactor with a three-phase fluidized catalyst bed. The fluidized bed allows for more intensive mixing of the contacting phases, an isothermal reaction regime, and maintaining the conversion of the feedstock and the equilibrium activity of the catalyst at a constant level by continuously withdrawing part of the catalyst from the reactor and replacing it with fresh or regenerated. However, due to significant drawbacks, hydrodesulfurization and hydrocracking processes in a fluidized bed have not yet been widely used in oil refining. From industrially mastered processes original, the most technologically flexible and rather effective is the process of hydrodesulphurization of heavy oil residues “Hayval” developed by the French Institute of Petroleum. The process flow diagram is shown in fig. 98. The reactor block of installation consists of serially working protective R-1 and R-2 reactors, two consistently working main R-3 and R-4 reactors of a deep hydrodemetallization and two consistently working reactors of hydrodesulphurization – R-5 and R-6. Protective reactors R-1 and R2 operate in an interchangeability mode: when the catalyst in the operating reactor loses its demetalizing activity, switch to another standby reactor without stopping the installation. The duration of continuous operation of the reactors is: for protective reactors – 3-4 months, and for the rest – 1 year. The feedstock (fuel oils, tars) is mixed with hydrogen-containing gas, the reaction mixture was heated in the furnace F-1 to the desired temperature and subsequently fed to the main reactor and to the protective reactors of hydrodemetallization and hydrodesulfurization. Products of hydrodesulphurization are subjected to hot separation in hot and cold gas separators, then to stabilization and fractionation on atmospheric and vacuum columns. As the catalyst is used the alumina modified by metals for hydrogenation. The catalyst has a rough surface with the pores in the form of “hedgehog”.

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Figure 98 – Process Flow Diagram of Installation of hydrodesulphurization of oil residues of the French Institute of Oil: CS – cold separators, HS – hot separators, HCG – hydrogen containing gas, AS – amine scrubber, AR – Atmospheric rectification, VR – Vacuum rectification, F-1 – furnace [12].

LITERATURE to Part VII 1. 1. Жермен Д.Э. Каталитические превращения углеводородов. – М.: Мир, 1972. – 308 с. 2. Гудун К.А. Каталитическая переработка полиароматических углеводородов...дисс. на соиск…канд.хим.наук // Караганда, Казахстан, 2012, 123 с. 3. Sassykova L.R. Theory and technology of catalytic petrochemical productions: educational manual.- Алматы: Казақ университеті.-2018.-296p. 4. Sassykova L.R. Chemistry and physics of petroleum, gas and coal. Eduactional manual, Алматы: Казақ университеті.-2017.-196p. 5. Калечиц И.В. Химия гидрогенизационных процессов в переработке топлив. – М.: Химия, 1973. – 336 с. 6. Лозовой А.В, Дьякова М.К. О скоростях гидрирования ароматических и непредельных углеводородов // ЖОХ. – 1940. – Том 10. – С. 1-10. 7. Беренц А.Д., Борисова Л.В. и др. Гидрирование непредельных углеводородов на алюмокобальтмолибденовом катализаторе // Тр. Инст. горючих ископаемых. – 1967. – Т. 23, №3. – С. 174-183.

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8. Гейтс Б.К., Кетцир Дж., Шуйт Г. Химия каталитических процессов, пер. с англ. – М.: Мир, 1981. – 552 с. 9. http://www.mining-enc.ru/g/gidrogenizaciya/ 10.Barrio V.L., Arias P.L., Cambra J.F., Guemeza M.B., Pawelec B., Fierro J.L.G. Hydrodesulfurization and hydrogenation of model compounds on silica– alumina supported bimetallic systems// Fuel, 2003, V.82, № 5, P.501–509. 11.Калыкбердиев М.К., Сасыкова Л.Р., Масенова А.Т., Жумабай Н.А. Катализаторы для жидкофазного гидрирования ароматических углеводородов и бензиновых фракций // Всероссийская научно-практическая конференция «Перспективы развития и современные проблемы образования, науки и производства», посвященная 50-летию города Нижнекамска, 20 мая 2016 г., г. Нижнекамск (Татарстан, Россия), 2016, Материалы конференции, с.26-27. 12.Ахметов С.А. Технология глубокой переработки нефти и газа. – Уфа: «Гилем», 2002. – 673 с. 13.WiJngaarden, K.R. Westerterp. Industrial catalysis. Optimizing catalysts and processes.-Willey-VCH VerlagGMb&KGaA, Wenheim, Germany, 2006.-507p. 14.Chorkendorff I., Niemantsverdriet J.W. Concepts of modern catalysis and kinetics.-Willey-VCH VerlagGMbh&KGaA, Wenheim, Germany, 2003.-452 P. 15.Лебедев Н.Н. Химия и технология основного органического и нефтехимического синтеза. – М., Химия, 1988. – 592с. 16.Магарил Р. З. Теоретические основы химических процессов переработки нефти. – Л.: Химия. Ленингр. Отд-ние, 1985.– 285 с. 17.Мановян А.К. Технология переработки природных энергоносителей.М.: Химия, Колос С, 2004.– 456 с. 18.Леффлер У.Л. Переработка нефти. / М.: ЗАО «Олимп-Бизнес», 2011. – 224 с.

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CONCLUSION    Aromatic mono-, di- and polyamines, due to their high reactivity, are widely used in the production of various compounds: synthetic dyes of various shades (for photography, in the paint and varnish industry, for painting natural and synthetic fibers), photochemicals, fuel stabilizers and additives lubricating oils, chemical plant protection products, synthetic fibers, sorbents, medicines, etc. The most important way of obtaining amines from nitro compounds is catalytic reduction by hydrogen on catalysts. It was first realized by M. M. Zaitsev in 1872 with the passage of nitrobenzene and hydrogen vapor over platinum black. After 30 years, Sabatier showed that nickel and a number of other metals can be used as catalysts for this reaction. A major contribution to the study of the catalytic reduction of nitro compounds was made by scientists from the USSR, the CIS, Russia and Kazakhstan. The use of liquid-phase catalytic reduction of nitro compounds makes it possible to carry out the process at sufficiently low temperatures, which leads to a significant reduction in energy costs and the explosion of the system. At present, in some countries, including the CIS, this method of reducing nitro compounds in solvents has become one of the main ways of obtaining amines. Due to the use of solvents, the process is carried out under milder conditions than with the vapour method. This method of synthesizing amines is more environmentally friendly, the target amine products are formed with rather high yields. Hydrogenation of aromatic hydrocarbons is an important petrochemical process. Using this process it is possible to improve the quality of fuels. At hydrogenation of benzene cyclohexane is produced, which is used for the production of adipic acid, caprolactam, cyclohexanol. Interest in cyclohexane arose in 1938 in connection with the development of nylon by DuPont, which proposed the use of cyclohexane as the preferred feedstock. All cyclohexane is used to produce 3 intermediate products: caprolactam, adipic acid and hexamethylenediamine, a raw material for the production of synthetic nylon-6 and nylon-66 fibers, as well as resins. The market for nylon 278

fibers includes hosiery, upholstery, carpets and tire cords. Nylon resins are technical plastics that are used in the production of gears, washers. Other applications of cyclohexane are industrial processes that require the participation of a solvent, such as the dissolution of fats, oils, and rubber. In addition, it is used to remove paint. A certain amount of cyclohexane is used as a solvent in the production of polyolefins and resins. In the presence of selective hydrogenating catalysts, almost no by-products are formed during the hydrogenation of benzene, and thus the high purity of the resulting cyclohexane is ensured. Hydrogenation of aromatic hydrocarbons provides a wide range of different compounds, such as cyclohexylamine, tetralin, decalin through the attachment of hydrogen via the double bonds of aromatic rings. Hydrogenation processes often turn out to be stages of multistage syntheses of organic compounds – solvents, surfactants. The monograph is divided on 7 Parts and 18 Chapters. It describes the general issues of different ways of catalytic reduction of aromatic nitro compounds and hydrocarbons; adsorption of starting compounds and products of reactions; various mechanisms of catalytic reduction of aromatic nitro compounds; activation of hydrogen on active centers of catalysts and quantum-chemical description of the reactivity of molecules. A separate part of the monograph is devoted to the description of the apparatus used for hydrogenation in the liquid phase. Monograph can be useful to specialists working in the field of catalysis, fine organic synthesis, chemical technology of organic substances, oil refining and petrochemistry; bachelors, masters and doctoral students studying in the specialties “Chemistry”, “Petrochemistry”, “Chemical Technology of Organic Substances”, students, undergraduates and doctoral students, when studying disciplines “Technology of processing natural and oil associated gas”, “Technology of oil, gas and coal”, “Modern aspects of petrochemistry”, “Technologies for processing natural, oil associated and technological gases”, “Modern technologies of oil, gas and coal”, “Syntheses based on liquid and solid hydrocarbons of oil origin”, “Chemistry and physics of oil, gas and coal” “Structure of matter”, “Theory and technology of catalytic petrochemical productions”.

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GLOSSARY A Acid-base catalysis is a catalytic reaction, where acids or bases are involved as catalysts. In general, this term can refer to both Brönsted and Lewis acids and bases. However, more specific terms for electrophilic and nucleophilic catalysis are also used for Lewis acids and bases. In the case of Brönsted acids and bases, the specific and general acid-base catalysis are distinguished, which are determined by the features of the mechanism of the catalytic process. Acidic center is the grouping of atoms in the structure of a macromolecule or on the surface of a solid body, which is capable of attaching a base with transferring it to a conjugated acid. Acidity is the ability of a substance to interact with a base. In this case, the base passes into the conjugate acid. The activation energy, for an elementary chemical transformation, is the minimum energy of the reagents, sufficient to overcome the barrier at the surface of the potential energy that separates the reactants from the products. If the reaction is complex (consisting of several stages), this term usually indicates an effective (apparent) activation energy. Activation of the catalyst is a technological stage which prepares the catalyst for work with reactionary mixture. In some cases it is convenient to carry out activation of the catalyst after its loading into the reactor. At a stage of activation there is a final formation of necessary phase structure of the catalyst, for example, reduction, sulfonation, oxidation, dehydroxylation (removal of water), addition of the activator and other processes are carried out. Activation of chemical reactions is a phenomenon of increasing the rates of chemical reactions in the presence of acids or bases, accompanied by their consumption. Such processes are sometimes called pseudo-catalytic processes. For such reactions, the mechanism of intermediate reaction of the reactants with the acid or base is similar to the true catalytic reaction, however, catalyst regeneration does not occur at the end of the catalytic cycle. Example: hydrolysis of carboxylic acid esters is accelerated in the presence of acid and represents a true catalytic reaction. The hydrolysis of amides of carboxylic acids should be considered as a pseudocatalytic reaction, since it is also accelerated in the presence of an acid, but at the end of the catalytic cycle, an ammonium ion is formed instead of H+. Activated adsorption is a chemical adsorption characterized by a significant activation energy. In this case, the adsorption equilibrium is reached very slowly or is not achieved at all. The activator is a substance which interacts with the catalyst and causes increase in speed of catalytic reaction, but itself at the same time isn't spent. For example, the rate of polymerization of α-olefins on metallocene catalysts increases significantly when methylaluminoxane is added to the system. The active center is an ensemble of atoms in the structure of the catalyst (complex compound or part of the surface) containing the minimum sufficient number of atoms of specific elements for the catalytic process to proceed. The active centers in the heterogeneous catalyst can be, for example, clusters from adjacent surface

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atoms, or particles adsorbed on the catalyst surface. In the case of a homogeneous metal-complex catalyst, the active center is usually considered to be the central metal atom together with the ligand environment. Active phase – this term has the same meaning as the active component. It is used in those cases when it is required to specify the phase composition of the active component under catalytic process conditions. Example: the melt of potassium pyrosulfonadate is the active phase in the vanadium catalyst for the oxidation of SO2 into SO3. Active component is the substance which is a component of the multicomponent catalyst and directly carrying out catalytic transformation. Other components of the catalyst perform support functions, for example, are the carrier or the promotor. Example: for the put (deposited) catalyst of hydrogenation Ni/SiO2 an active component – metal nickel, while silicon oxide – the carrier. The Adams catalyst is a catalyst for reduction and hydrogenolysis in organic synthesis. The active phase of the catalyst is platinum black, formed in situ from platinum dioxide hydrate under the action of hydrogen H2. Additives are chemicals added to petroleum products in small amounts to improve quality or add special characteristics. Adhesion coefficient is the relation of quantity of the adsorbed molecules for a unit of time to the frequency of concussions of molecules with the surface of adsorbent. The coefficient of adhesion depends on fill factor of a surface, temperature, structure of a surface of adsorbent and other parameters. Adiabatic reactor is a reactor in which chemical transformations are carried out in adiabatic mode. In such a reactor, there are no systems for removing heat, or such systems do not contact directly with the catalyst bed. Adiabatic reactors are used in large-scale production, if the process proceeds relatively slowly and is not accompanied by a significant release of heat. Adsorbate is a substance (molecule, ion or atom) adsorbed on the surface of a solid due to physical (physical adsorption) or chemical (chemisorption) interaction between a solid and a substance. Adsorbed substance – see adsorbate. Adsorbent is a condensed substance on the surface of which adsorption takes place. Adsorption is a process in which a substance (molecule, atom, ion) accumulates on the surface of a solid (or, more rarely, a liquid) due to physical (physical adsorption) or chemical (chemisorption) interactions between matter and the surface. The number of adsorbed molecules is determined by the adsorption equilibrium. Depending on the type of interaction, physical and chemical adsorption is distinguished. The adsorption center is a specific place on the surface of the adsorbent, where the adsorption of the molecule takes place. Adsorption centers can be surface defects or surface functional groups (for example, the Brönsted acidic center). The adsorption complex is a group of atoms including an adsorbed substance and a part of the adsorbent surface that directly interacts with the adsorbate. Adsorption equilibrium is a thermodynamic equilibrium established between a substance in a homogeneous phase and in an adsorbed state on the adsorbent surface.

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The adsorption equilibrium is characterized by the adsorption constant, the temperature dependence of which is determined by the heat of adsorption. Adsorption isobar is the dependence of the equilibrium amount of adsorbed molecules on the temperature, measured at a constant partial pressure of the adsorbent in the gas phase. Adsorption impregnation is an impregnation method in which the application (putting) of a substance is achieved by adsorption of the precursor (the predecessor) of the active component from the solution onto the surface of the carrier. This method makes it possible to obtain a different distribution of the active component along the grain of the catalyst, including the "crust" catalysts widely used in industry (the active component is distributed in the outer layer of the carrier granules). Adsorption isotherm is the dependence of equilibrium quantity of the adsorbed molecules on the partial pressure of an adsorbtive in a gas phase measured at a constant temperature. The adsorption isotherm of Langmuir is an adsorption isotherm constructed for a monolayer adsorption model on a homogeneous surface in which the interaction between adsorbate molecules can be neglected. The adsorption isotherm of Langmuir is the simplest kind of isotherm and is often used as an assumption for constructing kinetic models. Adsorption with charge transfer is a chemisorption, accompanied by the reduction or oxidation of the adsorbent. For example, the adsorption of triphenylamine on aluminosilicate is accompanied by transfer of charge to the adsorption center of the aluminosilicate. Adsorptive is a substance that is in a homogeneous phase and is potentially capable of adsorption on the phase interface. Agglomerates are particles of matter obtained by combining smaller particles, for example, associates from primary particles. Aging of the catalyst is a slow and irreversible decrease in the catalytic activity as a result of a change in the structure of the catalyst. Aging of the precipitate is a transformation in the precipitated substance that occurs while the sediment is under the mother liquor. With the aging of the sediment, various physical and chemical processes take place, leading to crystallization, coarsening of particles, changes in phase and chemical composition. As a rule, aging is accompanied by a decrease in the surface area of solid particles in the sediment. Air fin coolers is a radiator-like device used to cool or condense hot hydrocarbons Alkanes (paraffins, saturated hydrocarbons) are a homologous series of noncyclic hydrocarbons that do not contain double or triple bonds. The simplest alkane is methane, the subsequent terms of the series (propane, butane, pentane, etc.) are obtained by adding to one ethylene one carbon atom – a methyl group. The general formula for the series is CnH2n+2. Alkenes (unsaturated hydrocarbons, olefins) is a homologous series of noncyclic hydrocarbons containing double bonds. The simplest member of the series contains two carbon atoms – ethylene. Next followed by propylene, butylenes, etc. The general formula for the series is CnH2n. Alkylation is the process of introducing an alkyl substituent into an organic molecule. It is used, for example, in the production of ethylbenzene: in this case,

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benzene is alkylated with ethylene. A process using sulfuric or hydrofluoric acid as a catalyst to combine olefins (usually butylene) and isobutane to produce a high-octane product known as alkylate. Alicyclic hydrocarbons are cyclic (ringed) hydrocarbons in which the rings are made up only of carbon atoms. Aliphatic hydrocarbons are hydrocarbons characterized by open-chain structures: ethane, butane, butene, acetylene, etc. Amination is the introduction of the amino group NH2 in the composition of various organic compounds, most often with the help of alkali metal amides (Chichibabin’s reaction). Amines are compounds formed by replacing hydrogen atoms in an ammonia molecule with organic radicals. Amines are divided into primary R2NH and tertiary R3N. By the number of amino groups in the molecule, mono-, di-, triamine, etc. are distinguished. Amines of the aromatic series can be obtained by the Zinin reaction by reduction of the corresponding nitro compounds or from phenols and ammonia. Amines are a very important class of organic compounds, which are intermediates in the manufacture of azo dyes and other dyes, many drugs, high molecular compounds, etc. Amino acids are organic (carbinic) acids containing one or more amino groups. Depending on the position of the amino group relative to the carboxyl, there are distinguished α-, β-, γ-amino acids, etc. For example, CH3-CH(NH2)-COOH-αaminopropionic and H2N-CH2-CH2-COOH-β-aminopropionic acids. The number of carboxyl groups is distinguished by mono- and dicarboxylic acids, by the number of amino groups – monoamino acids, diamino acids, etc. Amino acids are widely distributed in nature. The structure of proteins includes only α-amino acids. Almost all natural amino acids contain an asymmetric carbon atom in the molecule and exhibit optical isomerism, and representatives of only one (namely, L-) a number of antipodes occur in organisms. Among natural amino acids, there are both aliphatic and cyclic amino acids. Amino acids are colorless crystalline substances with melting point 220315ºC, soluble in water. Most amino acids are insoluble in organic solvents or poorly soluble. Aqueous solutions of amino acids have a neutral reaction. Amino acids are obtained by the hydrolysis of proteins or synthetically as a result of the interaction of ammonia with halogenated acids. More than 20 amino acids have been isolated from proteins. Amino acids play an important role in the nitrogen metabolism of living organisms: they are the source of the formation of substances essential for life: proteins, peptides, enzymes, hormones, etc. Amino acids, synthesized in the body of humans and animals, are called interchangeable, not synthesized – irreplaceable. Many amino acids find applications in medicine: for gastrointestinal nutrition of organisms, in the treatment of burns, anemia, liver diseases, for feeding animals, etc. Amino acids are also used in the production of polymeric materials and artificial fibers. Amino alcohols are organic compounds containing hydroxy and amino groups. Amino alcohols can be obtained by adding ammonia or amines to olefin oxides. The reaction of ethylene oxide with ammonia produces mono-, di- and triethanolamines. The greatest practical importance of amino alcohols are ethanolamines. Most alkaloids, for example, ephedrine, cocaine and others, are derivatives of amino alcohols. One of the major hormones – an adrenaline belongs to amine alcohols.

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Ethanolamines are used in the industry for purification of gases of sulfur compounds of carbon dioxide. Amino group is a radical – NH2, a part of the primary amines. Aminophenols (oxyanilines) H2NC6H4OH are crystalline substances. Three isomers are known: o-aminophenol, melting point 174ºC, m-aminophenol, melting point 123ºC, p-aminophenol, melting point 186ºC – amphoteric compounds: they form salts with acids and alkalis. The general method of preparation is to reduce the corresponding nitro- or nitrosophenols. Aminofenol is used in the production of sulfur and other dyes. The salts of p-aminophenol and its N-methyl derivative (methanol) belong to the number of developers widely used in photography. Aniline (aminobenzene, phenylamine) C6H5NH2 is the simplest aromatic amine; a colorless liquid with a peculiar smell, rapidly boils in the air, b.p. 184ºC. Poorly soluble in water, mixed with many organic solvents mixed in all respects. Aniline dissolves some metals (Na, K, Ca, Mo, etc.) with the formation of their derivatives – metalamides. Aniline is the most important product of the chemical industry. During the oxidation of aniline, a stable dye-aniline black is formed: hydrogenation – cyclohexylamine C6H11NH2, from which caprolactam is obtained. Aniline is used for the preparation of developers, vulcanization accelerators of rubber, pharmaceutical preparations, various aniline and azo dyes, in analytical chemistry, etc. Aniline is toxic. Anthracene is an organic chemical compound, in the molecular structure of which there are three benzol rings, connected together. Chemical formula С14Н10. Anthracene is obtained from coal tar. The classical method of laboratory production of anthracene is cyclodehydration of o-methyl or o-methylene-substituted diaryl ketones in the so-called Elbs reaction. It is similar in chemical properties to naphthalene (it is easily nitrated, sulfonated, etc.), but differs from it in that it more readily enters the addition and oxidation reactions. Anthracene can be photodimerized by UV radiation. This leads to a significant change in the properties of the substance. Anthracene is the raw material for the production of anthraquinone, numerous dyes, for example alizarin. In the form of crystals it is used as a scintillator. API Gravity is an arbitrary scale expressing the density of petroleum products. Apparent density is the density of a solid porous substance, which is calculated as the ratio of the mass of the particle to its volume. Since part of this volume falls on the pores inside the particle, the apparent density of the porous substance is less than its true density. Aromatic hydrocarbons are organic compounds containing in their structure a cycle with conjugated double bonds. In the petrochemical industry under this name usually involve benzene, toluene and xylenes (ortho-, meta- and para-). Aromatic nitro compounds are a group of organic substances, headed by nitrobenzene and formed from benzene and its homologues (toluene and xylene), naphthalene and anthracene by replacing one or more atoms with a nitro group. The nitro group can be replaced, along with halogen and some alkyl radicals, in almost any place of the ring. Nitro compounds that have the most important industrial significance include nitrobenzene, mono- and dinitrotoluenes, trinitrotoluene (TNT), tetryl, mononitrochlorobenzenes, nitroanilines, nitrochlorotoluenes, nitronaphthalene, dinitrophenol, picric acid (trinitrophenol), and dinitrocresol. Aromatics are organic compounds with one or more benzene rings.

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Asphaltenes are the asphalt compounds soluble in carbon disulfide but insoluble in paraffin naphthas. They are the most high-molecular components of oil. Associated petroleum gas, APG is an oil product. In reservoir conditions, it is dissolved in oil and released when the fossil is extracted to the surface. The composition of associated gas varies greatly, but its main component is methane, as well as a certain amount of ethane, pentane and butanes, etc. Associative adsorption – see nondissociative adsorption. Associative desorption is the reverse process of dissociative adsorption. Asymmetric catalysis is the production of optically active substances by catalytic reactions from optically inactive raw materials. The catalyst in this case must be a chiral substance, for example, a metal complex compound with chiral ligands. This can also be the case when a chiral modifier is added to a conventional catalyst that does not have optical properties. Asymmetric catalysis is widely used in the industry for the synthesis of biologically active substances, drugs, etc. Atactic polymer is a polymer in which the orientation of the side fragments of the molecular chain relative to the axis of the chain and each other is chaotic. Atmospheric Column is a distillation unit which operates at atmospheric pressure. Autocatalysis is the acceleration of a chemical reaction under the influence of a product or an intermediate of this reaction. Example: hydrolysis of esters, leading to the accumulation in the reaction system of an acid having a catalytic effect in hydrolysis. Autoclaves are devices in which reactions under pressure are carried out. They come in two classes – low-pressure autoclaves designed for pressures up to 10 atm, and high pressure autoclaves up to 1,000 atm. The latter are more often used in chemical laboratories. Autoclaves are thick-walled metal vessels, often cylindrical or spherical. High-pressure autoclaves were first widely applied by Ipatiev, whose work in this area dates back to 1903. The Ipatyev autoclave (or bomb) is a forged cylinder with a flange head that joins the autoclave body with the help of the Ipatiev shutter. Mixing of the contents is achieved by tilting the autoclave and its slow rotation. Such an autoclave is very convenient to handle. It is easy to wash. An example of using such a device may be the process of hydrogenation of benzene to cyclohexane. Azides are salts of nitrous acid HN3, as well as compounds containing the group – N3. Most azides are explosive, with the exception of alkali metal azides. Azides of heavy metals explode with a light shock, touch or friction, even in wet conditions. Azides, mainly lead azide, are used as initiating explosives. Azines are the hexatomic heterogeneous organic compounds containing at least two heteroatoms, one of which is nitrogen atom. Representatives of diazines are orthodiazine, pyrimidine pyrazine, an example of connection in which the azine core is condensed with other cyclic system is purine. Some azines, especially derivatives of pyrimidine and purine, play an important role in vital processes, are part of nucleic acids, vitamins, alkaloids, etc. Synthetic azines are used in medicine: aminazine in psychiatric and surgical practice, luminal and veronal – hypnotics, piperazine (in the form of a salt with adinic acid) – anthelmintic drug, sulfadimezin – an effective drug for infectious diseases. Some azines are part of synthetic dyes.

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Azobenzene C6H5N = NC6H5 – orange-red rhombic crystals, Tmelting=68ºC; it does not dissolve in water, it dissolves in alcohol, naphtha, ether, glacial acetic acid, concentrated sulfuric acid. Under intensive illumination, it transforms into an unstable cis-form, a more saturated color, melting at 71ºC and spontaneously turning back into a trans isomer. Azobenzene is obtained by reduction of nitrobenzene with zinc dust or azoxybenzene, electrochemical reduction of nitrobenzene etc. When reducing zinc in an alkaline medium azobenzene converted into hydrazobenzene, in acetic acid medium – into aniline. Azobenzene is oxidized by oxidants to azoxybenzene. Azo compounds are organic compounds characterized by the presence of azo groups -N = N- linked to two aromatic or (rarely) other radicals. The most common method of obtaining azo compounds is the azo coupling reaction. Aromatic azo compounds are especially brightly colored when there are -OH, -NH2, -SO2H, COOH, etc. in the molecule. Azo dyes are organic dyes as a part of which there are one or several azo-groups – N=N-, the bound to aromatic groups. They are the most widespread class of the synthetic dyes which are applied to dyeing of fibers, plastic, skin, paper, rubber and other materials. Representatives of azo dyes are methyl orange and congo red, applied as indicators acid – the main titration. Azomethinic dyes are dyes, which contain the azomethine group -N = CH-. Azomethinic dyes are used for dyeing synthetic fibers, as desensitizers of photographic emulsions, as well as in color photographs. B The base state is the state of the chemical substance associated with the lowest energy. Photochemistry usually refers to the electronic base state. The base center is a group of atoms in the structure of a macromolecule or on the surface of a solid that is capable of attaching an acid with transferring it to a conjugate base. Basicity is the ability of a substance to interact with an acid. At the same time the acid passes into the conjugate base. Bathochromic and gypsochromic effects is change in color in the direction of the towards deepening and, accordingly, increase color. Deeper is considered the color, which corresponds to the absorption band in the region of the spectrum with longer wavelengths and vice versa. On this basis, the colors are arranged in the following order:

Deepening of color→

Color Enhancement→

Colors Greenish-yellow From yellow to orange Red Purple Violet Blue Greenish Blue Blue-green

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The wavelength of the absorption band, 10-9 m 400-430 430-490 490-510 510-530 530-560 560-590 590-610 610-730

The direction of the color change depends on the substitution of substituents in the dye molecule, the pH of the medium, and the spatial structure of the dye molecule. The causes of this bathochromic and gypsochromic phenomenons are considered in the modern theory of chromaticity of organic compounds. Bending of the zone is the bending of the valence band or the conduction band in semiconductors on the surface due to the presence of the surface potential of the charge due to the adsorption of the substance (donor or acceptor) or due to the different distribution of defects in the near-surface region and in the volume of the substance. Bending is also formed due to a drop in potential when the semiconductor contacts the electrolyte. Bentonites are plastic clays of high quality, consisting of minerals of the montmorillonite group. The names of individual bentonite species are most often associated with the geographic location of their deposits. For example. bentonites were first discovered in the area of Fort Benton (USA), montmorillonite (France), gumbrin, ascanel and nalchikin (Georgia), shalbi (Azerbaijan), etc. In Georgia, these clays are also called “tabissabaniets”, which means “land for washing head”, in Crimea “keel”, which means “mineral soap”. Since ancient times, the detergents, bleaching and healing properties of these clays have been known. Bentonites are used to remove fat from wool, as well as in oil, food, perfume, rubber, coke, metallurgy and other industries. BET is the method of determination of specific surface area of solid bodies based on model of physical adsorption of molecules of gases (nitrogen, argon, etc.) with use of the accepted value of molecular cross section. The method has received the name on names of three scientists (S. Brunauer, P. Emmett, E. Teller) who have developed the corresponding model for polymolecular adsorption. Despite some shortcomings in the theoretical description, this method is widely used as a standard technique for determining the surface area of catalysts and adsorbents. Benzene, C6H6, is an unsaturated, six-carbon ring, basic aromatic compound. Benzene is the simplest and most important representative of aromatic hydrocarbons, a colorless, transparent, mobile liquid with a characteristic “aromatic” odor, b.p. 80.1° C, melting p. 5.533° C. For the first time benzene was isolated in 1825 by M. Faraday from the liquid condensate of the luminous gas. In 1865, A. Kekule proposed for the benzene formula of a six-membered cycle with alternating double and simple bonds. But there is still no graphic representation of the benzene formula, which completely reflects its structure and properties. Benzene is mixed with non-polar solvents, with absolute ethyl alcohol, acetone, in methanol is limitedly soluble. In 100 g of water at 25 °C, 0.18 g of benzene dissolves. In benzene, fats, oils, rubber, resins, alkaloids are readily soluble; iodine, sulfur and white phosphorus are insoluble. With water, benzene forms an azeotropic mixture used for the production of absolute C6H6 and C2H5OH. For benzene, substitution reactions are characteristic: halogenation, nitration, sulfonation, acylation, alkylation. Benzene is resistant to oxidizing agents: chromic acid, KMnO4. It burns with a smoking flame. In the presence of catalysts (Ni, Pt), benzene adds hydrogen to form cyclohexane. When the benzene is illuminated with ultraviolet rays, it adds chlorine to form hexachlorocyclohexane (hexachlorane). Benzene is extracted from coking products of coal or obtained by catalytic cyclization of aliphatic hydrocarbons of oil. Benzene is one of the most important products of the chemical industry, it is widely used in the production of dyes, pharmaceuticals, as a

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raw material for the production of synthetic rubber, plastics, explosives and as a solvent. Benzene is a physiologically active substance, acts on the nervous system, causes a change in blood composition and disrupts the normal function of the hematopoietic organs. Chronic poisoning with benzene can cause death. Liquid benzene strongly irritates the skin. Benzidine rearrangement is an intramolecular rearrangement of hydrazo compounds, which occurs under the influence of acids leading to the formation of benzidine derivatives. Benzidine rearrangement is widely used for the preparation of azo dyes from hydrazo derivatives of benzene, diamines of a number of diphenyl, for example, telidine, dianisidine, etc. Benzoic acid C6H5COOH is the simplest representative of mono-aromatic acids. Benzoic acid is a crystalline substance (leaves or needles), melting point 122.37°C; poorly soluble in water, better soluble in alcohol and ether. Benzoic acid is obtained by oxidation of toluene, from phthalic acid and other methods. Benzoic acid and its salts have a great bactericidal and bacteriostatic activity. Sodium benzoate is used for preserving foods, and benzoates of lithium, magnesium and calcium are used in medicine to treat gout and rheumatism. Benzoic acid derivatives are widely used in the organic synthesis of dyes, pharmaceuticals, as initiators of polymerization, in the food industry and in perfumery. Benzoic aldehyde (benzaldehyde) C6H5CHO is a colorless liquid with the smell of bitter almonds, b.p. 179°C; poorly soluble in water, mixed with many organic solvents. In air, it is rapidly oxidized to benzoic acid. In nature, benzoic aldehyde is found in bitter almonds, cherry leaves. It is obtained by oxidizing toluene MnO2 and H2SO4 in the presence of a catalyst or from benzene and carbon monoxide. Benzoic aldehyde is used for the synthesis of the dyes of the triphenylmethane series, fragrances, cinnamaldehyde, etc. Bidistillate is twice distilled (distilled) water used in working with high-purity substances in analytical chemistry and medicine. Bifunctional catalysis means catalytic reactions involving a bifunctional catalyst. Bifunctional catalyst is a catalyst, which contains two types of active centers, differing in their functions. Bifunctional catalysts are used when the reaction proceeds in two elementary stages, and these stages are catalyzed on active centers of different types. Example: for the hydrocarbon reforming process, bifunctional supported Pt/Al2O3 catalysts with acidic and dehydrogenating properties are effective. Binding molecular orbitals (BMOs) describe the state of an electron in the binding region. In the binding molecular orbitals, the electron density is concentrated between the nuclei. Bioelectrocatalysis is an acceleration of the electrochemical reaction in the presence of enzymes. Enzymes immobilized on the electrode carry electron transport directly between the electrode and the substrate, which does not require the participation of low molecular weight carriers. Blending is the process of mixing two or more petroleum products with different properties to produce a finished product with desired characteristics. A block (honeycomb) catalyst is a heterogeneous catalyst in which a carrier is used in the form of a monolithic block. Usually the block has a set of the parallel not crossed channels and is manufactured of ceramic silicate or metal materials. The

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active component is applied to the surface of the channels. The block catalyst is used in such processes where a large pressure drop is undesirable, for example, in the neutralization of exhaust gases in automobiles. Blowdown is the removal of hydrocarbons from a process unit, vessel, or line on a scheduled or emergency basis by the use of pressure through special piping and drums provided for this purpose. Blower is an equipment for moving large volumes of gas against low-pressure heads. Boiling range is the range of temperature (usually at atmospheric pressure) at which the boiling (or distillation) of a hydrocarbon liquid commences, proceeds, and finishes. Bottoms are column bottoms are residue remaining in a distillation unit after the highest boiling-point material to be distilled has been removed. Tank bottoms are the heavy materials that accumulate in the bottom of storage tanks, usually comprised of oil, water, and foreign matter. Bubble column is a fractionating (distillation) tower in which the rising vapors pass through layers of condensate, bubbling under caps on a series of plates. Brilliant green (tetraethyl-4,4’-diaminotriphenylmethane oxalate) C29H33N2O4 – golden-green powder; soluble in water, alcohol and chloroform to form green solutions. In the form of 0.1-2% aqueous or alcoholic solution is used as an antiseptic. Broad (wide) fraction of light hydrocarbons (BFLH or WFLH) is a product of processing associated petroleum or natural gas. It is a mixture of volatile hydrocarbons with a number of carbon atoms from 2 to 5 and a valuable petrochemical raw materials. The Brönsted acidic center (BCC) is a group of atoms as a part of any substance, capable to chip off H+ proton. Example: a bridging OH group on the surface of various oxides. The Brönsted acid is a substance capable of cleaving a proton of H+. Brönsted's base is the substance capable to attach H+ proton. Bulk density is density of solid-phase material calculated by division of mass of a sample into the volume occupied by a sample. At the same time volume considers the free space which is available in particles and between particles. Thus, bulk density depends both on porosity of individual particles, and on density of their packing which in turn depends on a geometrical form of particles (powder, granules, tablets, etc.). Butane-butylene fraction (BBP) is a gaseous product of a catalytic cracking process containing normal (unbranched) alkanes and alkenes with 4 carbon atoms. C Cadaverine – (from the Latin “Cadaver” – “corpse”) – is pentamethylenediamine, diaminopentane NH(CH)NH, a colorless liquid which is fuming in air, boiling point 180ºC; very soluble in water, alcohol, poorly soluble in ether. Cadaverine occurs in ergot, fly agaric, is found in cheese, brewer's yeast, in urine and excrement of people with cholera cystinuria, is formed when decay of protein substances. Cadaverine can be prepared by any method of synthesizing monoamines.

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Calcinating is a heat treatment of the catalyst at the increased temperatures. Calcinating is carried out as one of stages of preparation of the catalyst for the purpose of transfer of predecessors of various components to the necessary chemical composition. Also, the finished catalysts are subjected to calcination to carry out activation or regeneration processes. The capacity of a monolayer is the maximum amount of a substance (molecules, atoms or ions) per unit of regular surface centers, which can be adsorbed upon monolayer adsorption. In the case of chemisorption, the capacity of the monolayer is determined by the structure of the adsorbent and the chemical nature of the adsorbent. In the case of physical adsorption, it is assumed that the whole surface of the adsorbent is coated with a layer of tightly packed adsorbate molecules. Capillary impregnation is a method of impregnation in which the application (putting) of a substance is carried out by absorbing the solution into empty pores of the carrier under the action of capillary forces. Caprolactam (hexahydro-2H-azepin-2-one) is a cyclic amide (lactam) of εaminocaproic acid, colorless crystals; Tboiling = 262.5°C, Tmelting = 68-69°C. White crystals, readily soluble in water, alcohol, ether, benzene. In industry, benzene is the starting material for the production of caprolactam. When heated in the presence of small amounts of water, alcohol, amines, organic acids and some other compounds, caprolactam is polymerized to form a polyamide resin, from which a capron fiber is obtained. As of January 2014, caprolactam is the only substance entered by the cancer research agency into the list of non-carcinogenic substances. Capron is a synthetic fiber obtained from caprolactam. Ropes, fishing nets, staple cloth, stockings and a large number of other products are made of capron. Carbonylation is a catalytic process, the addition of carbon monoxide CO to a molecule of an organic compound (acetylenes, olefins, alcohols, aldehydes, etc.). The process is carried out in the liquid phase with the participation of nucleophilic molecules (water, alcohol) and in the presence of homogeneous catalysts (salts or metal complexes of Rh, Co, Ni, Fe, Ir, Os, etc.). Typical conditions are temperatures of 80-300°C and a CO pressure of 50-300 atm. The carrier is a solid phase component in the deposited (supported) catalyst, on the surface of which the active component is located. The main functions of the carrier are maintenance of an active component in a disperse state, creation of porous system, ensuring mechanical durability of granules of the catalyst. As carriers simple and complex oxides, and also materials on the basis of carbon are widely used. As a rule, the carrier in pure form doesn't show catalytic activity in relation to reagents and is inert substance. But also many examples when the carrier enters chemical interaction with the reactionary medium, or with an active component are known. Catalytic cracking is a secondary process of oil refining which essence consists in splitting of long hydrocarbonic molecules on shorter. The process of breaking up heavier hydrocarbon molecules into lighter hydrocarbon fractions by use of heat and catalysts. It is a source of petrochemical raw materials, such as propane-propylene fraction. Catalytic reforming is a secondary process of oil refining, the essence of which is the conversion of hydrocarbon chains into aromatic compounds – components of fuels and petrochemical raw materials.

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Catalysis is the phenomenon of initiation of chemical reactions or change of their speed under the influence of substances – the catalysts which are repeatedly entering intermediate chemical interaction with participants of reaction and restoring the structure after each cycle of intermediate interactions. At the same time the catalyst doesn't displace chemical balance of reactions. The catalyst is a substance that changes the rate of chemical reactions without shifting their chemical equilibrium, which repeatedly enters into an intermediate chemical interaction with reagents and regenerates its chemical composition after each cycle of such interactions. An important feature is that the catalyst is regenerated in each catalytic cycle, which allows the conversion of large amounts of reagents in the presence of a relatively small amount of catalyst. As a rule, for each chemical reaction it is required to select the specific catalyst. Practical application as catalysts is found by the most various substances – from solutions of acids and complexes of metals to complex solid-phase multicomponent compounds of strictly specified composition and a structure. The catalyst productivity is the amount of product produced per unit time, referred to the mass or volume of the catalyst. Catalytic activity is the rate of a chemical reaction, referred to the number of active catalyst centers or to a unit of mass or volume of the catalyst. The activity of the catalyst is determined by the nature and strength of the chemical bonds that are formed when reactants and reaction intermediates are bound to the catalyst. For a correct measurement of the catalytic activity should exclude the impact of mass and heat transfer. Catalyst durability is ability of particles of the solid-phase catalyst to maintain mechanical loadings. There are various experimental techniques for determination of durability (for example, durability on attrition, durability on crush). For commercial catalysts high durability allows to minimize losses during catalytic process, and also when transporting the catalyst and its loading in the reactor. The catalytic center is the center on which there are catalytic chemical transformations. If the number of the catalytic centers is unknown, for example, in case of a heterogeneous photocatalysis, for determination of specific parameters use BET surface measured on nitrogen adsorption. Catalytic combustion is a technology developed to produce thermal energy by oxidizing combustible compounds with oxygen in the presence of a catalyst. In the presence of catalysts, oxidation occurs at lower temperatures (without open flame). Multicomponent catalysts containing Cu, Cr, Pd, Mn and other components are used. Catalytic combustion is used in catalytic heat generators (KGT). The catalytic converter (neutralizer) of exhaust gases is a catalyst that provides removal of a number of harmful substances from exhaust gases in internal combustion engines. The main catalytic processes are oxidation of CO, postcombustion of hydrocarbons to CO2 and the reduction of nitrogen oxides. The most suitable are noble metal catalysts (Pt). The neutralization process is complicated due to temperature fluctuations in the exhaust gases (from 200 to 1000°C) and changes in the composition of the gas mixture (from oxidizing with excess oxygen to reducing with oxygen deficiency). Catalytic cracking is a catalytic hydrocarbon cracking process carried out in the presence of acid catalysts. The main catalytic cracking reaction is cleavage of the C-

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C bond in particles with an electron-deficient carbon atom, which leads to the formation of an alkane and an alkene. Also are carried out an intensive skeletal isomerization in hydrocarbons and process of transfer of hydrogen which reduces quantity of the formed olefin due to formation of aromatic hydrocarbons and coke. Catalytic cycle is a system of elementary reactions with participation of the catalyst at which the sequence is closed, a cyclic process of binding and regeneration of the catalyst occurs and the conversion of the starting materials to the products. An important feature is that after completion of the catalytic cycle, the catalyst passes to the initial chemical state and the catalytic cycle can be repeated many times with the same catalyst. Catalytic erosion is the destruction of the catalyst in the dendritic mechanism of coke formation. Separate components of the catalyst are mechanically separated and carried away with the growth of primary dendrites, which can lead to the complete destruction of the catalyst. The catalytic reaction is a chemical reaction proceeding through a sequence of stages forming a catalytic cycle. The catalytic route of the reaction is proved by the fact that the catalytic cycle can be realized several times (the number of revolutions exceeds unity). Currently, more than 80% of all industrial chemical processes are carried out using catalytic reactions. Catalytic poison is a substance that forms strong chemical bonds (usually covalent) with atoms and ions entering the active sites of the catalyst to form catalytically inactive centers and, thus, leads to deactivation of the catalyst. In most cases, the catalytic activity and/or selectivity cannot be restored without significant change in reaction conditions. Special regeneration procedures are required, and most often the characteristics can only be partially recovered. The catalytic poison may be present as an impurity in a mixture of reagents, or it may enter the catalyst during the preparation stage. Typical poisons are sulfur and arsenic compounds, also the compounds of transition metals contained in raw materials can act as catalytic poisons. Catalytic photochemical reactions mean increase (change) in the efficiency of photochemical reactions during direct excitation of photosensitive reagents through the intermediate interaction of these reagents with certain compounds that act as catalysts (promoters) of the appropriate chemical transformation of the reagents. Sometimes this process may be identical to photocatalysis. Caustic wash is a process in which distillate is treated with sodium hydroxide to remove acidic contaminants that contribute to poor odor and stability. Chemical adsorption (chemisorption) is a kind of adsorption, as a result of which a chemical bond is formed between the adsorbent and the adsorbate. Chemisorption implies the rearrangement of electrons in the adsorbed molecule and is therefore characterized by sufficiently large values of the heat of adsorption (more than 80-100 kJ/mol), as well as specificity for the adsorbent-adsorbate pair. In addition, unlike physical adsorption, chemical adsorption can have activation energy, proceed irreversibly and be accompanied by dissociation of adsorbate. In processes involving a heterogeneous catalyst, it is assumed that chemisorption of at least one of the reagents is an obligatory step, without which a catalytic conversion cannot occur. The chemical theory of a catalysis is the theory of a catalysis considering the catalyst as chemical compound with characteristic properties which is capable to

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contact reagents and to form unstable intermediates which destruction leads to products. The chromaticity theory is a doctrine that considers the patterns of color dependence on the chemical structure of an organic compound. The body appears white when it equally reflects the rays of the entire visible part of the spectrum, black when it absorbs completely from the gray, when approximately equally, but not completely, absorbs each of them, and color-wise when selectively absorbs some of them. The sensation of color arises as a result of exposure to the optic nerve of electromagnetic radiation with frequencies in the range v = 4·1014-7.5×1014s-1, i.е. with wavelengths λ = 400·10-9 – 760 · 10-9 m. Closed pores are pores that do not communicate with the outer surface of the particle. Molecules from the surrounding space cannot penetrate into the closed pores, therefore, such pores can not participate in adsorption and catalysis. Coagulation is the process of combining (cohesion) of small particles in a dispersed system with the formation of larger particles. Example: as a result of coagulation, the sol passes into the suspension. Coalescence is the process of merging droplets or gas bubbles in disperse systems. Coenzymes are compounds with a small molecular weight that are located in the active center of the enzyme and participate together with the enzyme and substrate in the formation of the activated complex. Coenzymes can be various organic compounds or inorganic ions (K+, Mg2+, Mn2+, etc.). Some coenzymes form a strong complex with the structure of the enzyme (for example, flavin coenzymes) and remain in the structure of the enzyme at all stages of the catalytic process. Also weakly bound enzyme-coenzyme complexes are known in which the coenzyme can carry the substrate to another enzyme. Coke means the condensed aromatic hydrocarbons whose structure approximates to graphite. The formation of coke on the surface of catalysts is a harmful by-product of hydrocarbon processing. It is also a high carbon-content residue remaining from the destructive distillation of petroleum residue. Coking is a formation of coke on the surface of heterogeneous catalysts. Deposits of coke block the surface of the catalyst therefore activity can significantly decrease and change selectivity of the catalyst. Coking is one of the main reasons for the deactivation of catalysts used in refining processes (cracking, reforming, dehydrogenation, etc.). It is the removal of all lighter distillable hydrocarbons that leaves a residue of carbon in the bottom of units or as buildup or deposits on equipment and catalysts. Coking as a process is a thermal transformation and upgrading heavy residual into lighter products and by-product petroleum coke. A colloidal solution is a dispersed system occupying an intermediate position between true solutions and coarsely dispersed systems. The particles of the dispersed phase in the colloidal solution have a size from 1 to 100 nm. Colorimetric analysis (colorimetry, from lat. “color” and Greek “metroe” – measuring) – an analytical method based on the determination of the concentration of a substance in terms of the intensity of the color of solutions is determined visually, for example, by comparison with the scale of standard solutions, or by instrumental methods.

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Combustible gases are the natural gases having ability to burn. Usually consist of gaseous hydrocarbons (methane, ethane, etc.) and are satellites of oil although also purely gas fields are known. If combustible gas contains a significant amount of vapors of natural gasoline (gasoline), such gas is called fat, at very small content of natural gasoline or at its absence gas is called dry. Compensation is an effect of simultaneous increase in a preexponential multiplier of k0 and the seeming energy of activation of Ea. Such effect can be observed for a series of the different catalysts used for the same reaction. Complexometry (chelatometry, trilonometry) is a titrimetric method based on the formation of complex metal ions compounds with ethylenediaminetetraacetic acid and other aminopolycarboxylic acids called complexons. The disodium salt of ethylenediaminetetraacetic acid, EDTA (cohmplexone III, or Trilon B) is advantageously used. The hardness of water (the content of ions Ca2+ and Mg2+), the content of metals in various materials, pharmaceutical preparations are determined by the method. Condensate is a natural mixture of mainly light hydrocarbon compounds that are in a dissolved gas and are converted into a liquid phase, with a decrease in pressure, below the condensing pressure. It is the liquid hydrocarbon resulting from cooling vapors. Condenser is a heat-transfer device that cools and condenses vapor by removing heat via a cooler medium such as water or lower-temperature hydrocarbon streams. Condensation is transition of substance from gaseous state into a liquid or solid phase. In case of disperse system this term designate formation of heterogeneous system from homogeneous as a result of association of molecules, atoms or ions in units. Condenser Reflux is condensate that is returned to the original unit to assist in giving increased conversion or recovery. A conduction band is a set of a plurality of closely spaced free or only partially occupied electronic levels that occurs in an array of a large number of atoms that form a solid body in which electrons can move freely. The term is used for the description of electrical properties of metals, semiconductors and dielectrics. In terminology of semiconductors and a photocatalysis the conduction band specifies the lowest level of a conduction band to which the electrons located at the highest level of the valence band are transferred with energy of high energy of the forbidden band. Conjugated diene hydrocarbons (dienes) are non-cyclic hydrocarbons containing two double bonds separated by a single bond. A homological series is formed with the general formula CnH2n-2. The simplest representative is 1,3butadiene. Conversion is the ratio of the amount of reagent converted into products to the total amount of reagent fed to the reactor inlet. At the same time the amount of reagent can be measured in various units (mol number, weight, etc.). Cooler is a heat exchanger in which hot liquid hydrocarbon is passed through pipes immersed in cool water to lower its temperature. A copolymer is a polymer consisting of monomers of different types. Copolymerization is the process of formation of polymer chains from monomers of different types.

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Coronene, also known as superbenzene, is a polycyclic aromatic hydrocarbon consisting of six polycondensed benzene rings. The chemical formula is C24H12. It is a yellow substance soluble in organic solvents such as benzene, toluene and dichloromethane. It emits blue-blue light under the influence of UV rays. Its emission spectrum is asymmetric with the absorption spectrum and the number of bands of the spectrum and their intensity varies with the solvent. It was used as a molecular probe to determine the nature of the solvent, like pyrene. In nature it occurs in the form of a very rare mineral of carpitis. Not harmful to health, unlike most of their “relatives”. It has a faint smell of cyanoacryl. Cracking is the process of breaking C-C bonds in a hydrocarbon molecule to form fragments with a lower molecular mass by the application of heat and pressure, with or without the use of catalysts. This is one of the most important processes in oil refining, used to convert high-boiling oil fractions to components with a higher octane number. There are catalytic cracking and thermal cracking. Crude assay is a procedure for determining the general distillation and quality characteristics of crude oil. Crude oil is a naturally occurring mixture of hydrocarbons that usually includes small quantities of sulfur, nitrogen, and oxygen derivatives of hydrocarbons as well as trace metals. Crystallization is a process of formation of a crystal phase of solution, steam or other solid phase, usually by decrease in temperature or evaporation of solvent. Curing (vulcanizing, vulcanization) is the process of rubber formation from rubber under the influence of vulcanizing agents, for example, sulfur. It consists in the cross-linking of polymer chains of rubber with each other into a single spatial grid. Cycle gas oil means the process when the cracked gas oil returned to a cracking unit. Cyclohexane (hexamethylene, hexahydrobenzene) C6H12 is a colorless, readily mobile liquid, b.p. 80.74°C, mixed with many organic solvents. Nitrosation of cyclohexane (NOCl) produces cyclohexanoxime, used in the production of caprolactam. Cyclohexane is synthesized from benzene by catalytic hydrogenation, it is isolated from petroleum products. It is used as a raw material in the synthesis of organic compounds and as a solvent. D Deactivation of the catalyst is a partial reduction or complete loss of catalytic activity during the operation of the catalyst. This term unites a fairly wide range of different processes and phenomena responsible for reducing catalytic activity. The most frequent reasons for the deactivation of catalysts are the change in the chemical composition of the catalyst under the conditions of the reaction medium, the volatility of the active component, the interaction of the active component with the carrier to form new phases, the change in the dispersion of the active component, poisoning, crystallization, sintering, coking and catalyst contamination. Deamination is the cleavage of amino groups from organic compounds or substitution by other atoms or groups, for example, H, OH, OR, CN, CH3COO, etc. Deamination is widely used in organic synthesis, and plays an important role in

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biochemical processes, for example, cleavage of the amino group from amino acids under the action of specific enzymes or bacteria. Deasphalting is a process of removing asphaltic materials from reduced crude using liquid propane to dissolve nonasphaltic compounds. Debutanizer is a fractionating column used to remove butane and lighter components from liquid streams. De-ethanizer is a fractionating column designed to remove ethane and gases from heavier hydrocarbons. The degree of filling the surface (the degree of surface coverage) is the ratio of the amount of adsorbed material to the capacity of the monolayer. If the degree of filling is >1, the adsorption is multilayer. Sometimes the degree of surface filling is calculated as the ratio of the number of adsorbed molecules to the number of surface atoms. The degree of use of the inner surface, a dimensionless parameter, indicates the share of the inner surface in the catalyst granules that reacts with the reagents under the given process conditions. It depends on the specific catalytic activity, the effective diffusion coefficient and the shape of the catalyst granules. It can be calculated by division of observed speed of reaction to the speed of the reaction corresponding to the intra kinetic mode of course of reaction. Dehydrogenation is the process of splitting off a hydrogen molecule from an organic compound. In industry it is used to convert ethane, propane, and butane into olefins (ethylene, propylene, and butenes). The density of active centers – this term refers to solid phase catalysts and denotes the surface concentration of the active centers (i.e., the number of active centers per unit surface). Depentanizer is a fractionating column used to remove pentane and lighter fractions from hydrocarbon streams. The deposited catalyst is a heterogeneous catalyst in which the finely divided particles of the active component are located on the surface of the carrier. Example: in the Pt/Al2O3 hydrogenation catalyst, dispersed particles of metallic platinum (the active component) are deposited on the surface of alumina (carrier). The deposition is a step of preparing the supported (put) catalysts, as a result of which the precursor of the active component passes from the solution or from the gas phase to the surface of the solid support. Different methods of application have their own names (for example, impregnation, deposition-precipitation, etc.). Deposition-precipitation is a method of producing deposited catalysts that combines methods of impregnation and precipitation. The active component is applied to the surface from the solution in the form of a suspension, which is formed by the gradual addition of a precipitant to the impregnating solution, the surface of the carrier acts as the crystallization centers. The method is used in cases where the compound, which is a precursor of the active component, is poorly adsorbed on the surface of the carrier. Depropanizer is a fractionating column for removing propane and lighter components from liquid streams. Desalting is removal of mineral salts (most chlorides, e.g., magnesium chloride and sodium chloride) from crude oil.

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Desorption is the reverse of adsorption process. As a result of desorption, the adsorbed material passes from the interface to the volume of the adjacent homogeneous phase. Destructive hydrogenation is the process of processing poor hydrogen fuels in high-grade products by attaching hydrogen to unsaturated compounds at high temperatures and in the presence of a catalyst. Desulfurization is a chemical treatment to remove sulfur or sulfur compounds from hydrocarbons. Dewaxing is the removal of wax from petroleum products (usually lubricating oils and distillate fuels) by solvent absorption, chilling, and filtering. Diazoamino compounds – (triazenes) are organic compounds containing the characteristic group -N = N – NH -; the general formula is R’N = N-NHR”, where R’ is an aromatic radical and R” is any radical. Diazoamino compounds are yellow solids whose solubility in water depends on the nature of the substituents in the radical R’: the presence of COOH groups, SO3H promotes solubility in water. Diazoamino compounds are used in the textile industry for printing on cotton fabrics. Some diazoamino compounds are initiators of polymerization. Diazo compounds are compounds of the general formula R-N2X or R = N2, where R is an organic radical. Diazo compounds contain a grouping of two atoms bound to only one hydrocarbon radical; X – in the aromatic diazo compounds – acid residue or hydroxyl, in the aliphatic diazo compounds X is absent. For example, diazomethane CH2 = N = N, diazoacetic ether N = N = CH-COO2H5, phenyl diazonium chloride C6H5-N≡NCl. Aliphatic diazo compounds are used only for the laboratory synthesis of organic compounds. Aromatic diazo compounds are also used for the industrial synthesis of various compounds, especially azo dyes. Diazomethane CH2N2 is the simplest diazo compound of the fatty series; gas yellow with an unpleasant odor, this substance is highly toxic and explosive. An ethereal solution of diazomethane is used, which is safe at a temperature of about 20°C. Diazomethane is a very reactive compound containing an active hydrogen atom, reacts with metal and nonmetal chlorides. Diazomethane is obtained by the action of alkalis on nitrosomethylurethane, nitrosomethylurea, etc. Diazotting (diazotization) is the interaction between an aromatic amine and HNO2 in the presence of an excess of mineral acid, which results in the formation of an aromatic diazo compound. Usually, with diazotization, NaNO2 is used. The reaction takes place at a temperature of 0-25°C, depending on the amine. For example, aniline is diazotized at 0-5°C. The reaction was discovered in 1858 by P. Griss and is of great practical importance, especially in the production of azo dyes. Diesel fuel is the medium and heavy oil fractions used as fuel for diesel engines (with compression ignition). As diesel fuel, kerosene gas oil fractions of direct distillation and catalytic cracking of oil with a boiling range of 270-400°C, cetane number of 35-50 depending on the engine speed are used. Diethanolamine is a chemical (C4H11O2N) used to remove H2S from gas streams. Differential selectivity is the ratio of the rate of formation of the target product to the total rate of consumption of the reagent due to all reactions. Unlike integral selectivity, differential selectivity depends only on the temperature and composition of the reaction mixture, and does not depend on the type of reactor.

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Differential heat of adsorption is the thermal effect of adsorption, which is measured during a calorimetric experiment when a small portion of a substance is fed. A significant change in the differential heat of adsorption with increasing surface filling is usually attributed to the inhomogeneity of adsorption centers and/or to intermolecular interactions in adsorbed molecules. Differential mode of the reactor is the mode of operation of the ideal displacement reactor, in which the conversion of the initial reactants at the outlet from the reactor remains low. Under such conditions, it can be assumed that the entire volume of the catalyst interacts with the reaction mixture in which the concentration of the reactants is the same. Diffusion impregnation is an impregnation method in which the putting of a substance is carried out by diffusion from the solution into the pores of the carrier, previously filled with a pure solvent. Diffusion inhibition is a decrease in the rate of the catalytic process due to the low diffusion rate of the reagents. In the case of a heterogeneous catalyst, external diffusion inhibition is distinguished (diffusion of the substance from the volume to the surface of the catalyst) and intra-diffusion inhibition (diffusion of the substance inside the catalyst granules). Dimedrol (benzhydrol β-dimethylaminoethylene ether hydrochloride) (C6H5)2CH-O-CH2CH2-N (CH3)2·HCl-color crystals, melting point 166°C; well soluble in water and alcohol, with a bitter taste. Dimedrol is one of the main antihistamines, it is used in the treatment of various allergic diseases (urticaria, fever), or complications from drugs, radiation, sea and air diseases, at vomiting, insomnia, etc. Dinitrophenyls C6H3(NO2)2OH are colorless or yellowish crystalline substances with strong acid properties, poorly soluble in cold water, soluble in organic solvents. All six isomers are known. Dinitrophenyls are prepared by nitrating phenols or nitrophenols, as well as by hydrolysis of the corresponding dinitrobenzenesulfonic acids. Dinitrophenyls are explosive, poisonous, strongly irritate the skin and mucous membranes, dramatically increase the metabolism in cells and body temperature. The nitration product of shale phenols, nitrophene, is used as a fungicide insecticide. Dinitrophenyls are used in the production of synthetic dyes, such as herbicides and insecticidal fungicides, as well as in analytical chemistry as indicators for the determination of pH. Diphenyl is a polynuclear aromatic compound. The formula is C12H10. Colorless or white crystals, with a specific odor. Insoluble in water, soluble in most organic solvents. It is weakly reactive in general reactions of aromatic hydrocarbons (nitration, sulfonation, etc.) It is used as a precursor in the synthesis of polychlorinated biphenyls, as well as other compounds used as emulsifiers, insecticides and dyes. Diphenylamine C6H5-NH-C6H5 are white crystals with a weak characteristic odor, darkening in light, melting point 54°C; soluble in water, soluble in organic solvents and concentrated mineral acids. Diphenylamine is used for organic synthesis, in the production of dyes, for the stabilization of pyroxylin powders, the determination of oxidants (HNO3, O3, etc. give a blue color with it) as an indicator. Diphenylmethane is an organic compound of the hydrocarbon class, a methane derivative, in the molecule of which two hydrogen atoms are replaced by phenyl groups. Chemical formula C13H12. Radical of diphenylmethane ((C6H5)2CH-) –

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benzhydryl. Diphenylmethane is a colorless transparent crystal with a geranium smell, insoluble in water, but readily soluble in organic solvents (benzene, diethyl ether, chloroform) and liquid sulfur dioxide. Due to the presence of the methylene group and benzene rings, diphenylmethane has the properties of both aliphatic and aromatic compounds: hydrogen atoms in the methylene group are capable of being replaced by halogen atoms, a nitro group or other functional groups. Diphenylmethane is used as a solvent in the paint industry and as a perfume for soap. A number of diphenylmethane derivatives serve as pesticides, fungicides and bactericides. The dispersed phase is a finely divided substance in the composition of a dispersed system. Dispersing is the crushing or grinding of macroscopic particles of matter. Dispersion is a quantity that is equal to the ratio of the number of surface atoms to the total number of atoms in the particle. Dispersion is inversely proportional to the particle size. The higher the dispersion of the particles, the smaller their size and, consequently, the higher the fraction of surface atoms. The dispersion medium is a part of the disperse system, in the volume of which the disperse phase is distributed. The dispersion system is a heterogeneous system containing a finely divided substance (dispersed phase), which is distributed in the volume of some other substance and does not mix with it (dispersion medium). Dissociative adsorption is chemisorption, during which the adsorbed molecule breaks up into two or more fragments. Example: dissociative adsorption of hydrogen H2 on metals leads to the formation of two Н⋅ radicals on the metal surface. Distillate are the products of distillation formed by condensing vapors. Distillation is the physical and technological process of separation of mixtures of liquids based on differences in the boiling points of the components. Doping is the formation of a solid solution when small amounts of foreign atoms are added to the crystal lattice of a nonmetallic catalyst. The term is generally applied to catalysts that are semiconductors. Doping changes the electronic properties of the catalyst, which can affect the rate of catalytic conversion. Downflow is a process in which the hydrocarbon stream flows from top to bottom. Drip analysis is a qualitative or semi-quantitative chemical analysis, in which the solution of the test substance and the reagents are taken in small amounts (a few drops). The reaction is carried out on filter paper, a drop glass, a porcelain plate. Due to speed and convenience, high sensitivity and selectivity, drip analysis is widely used to control the purity of various substances, for the rapid analysis of ores and minerals in the field, for various technical biochemical analyzes, for research works, etc. Dry gas is natural gas with so little natural gas liquids that it is nearly all methane with some ethane. Drying is the stage of preparation of catalysts, as a result of which excess solvent is removed from the catalyst. Typically, drying takes place at elevated temperatures, but without any chemical transformation in the catalyst structure. Dry stripped gas (DSG) is a product of processing associated petroleum or natural gas. It is a methane with minor impurities of other hydrocarbons. It is used mainly as a fuel.

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Dynamites (nitroglycerin explosives) are blasting explosives containing significant amounts of nitroglycerin. Dynamites are mixtures of nitroglycerin with powdered fillers: inert (kieselguhr, talc) or active (charcoal, a mixture of wood flour with nitrate, etc.). More stable are gelatin-dynamites made on the basis of nitroglycerin, gelatinized (up to 10%) by colloxylin. One of the most powerful explosives, produced on the basis of nitroglycerin (7-10% colloxylin), is gelatin explosive. Working with dynamite requires special care. E The effective (apparent) activation energy is the value of the activation energy of a complex chemical process, determined experimentally from the tangent of the slope of the graph constructed in Arrhenius coordinates (coordinates log (k) -1/T, where k is the rate constant, and T is the temperature). Effective density is the density of solid phase catalysts, determined on the basis of the volume of liquid that is displaced by the sample when it is placed in this liquid. The effective density values can differ significantly for different liquids due to the fact that a different degree of penetration of liquids into the pores of the catalyst is observed. The effective diffusion coefficient is the average diffusion coefficient in solid porous particles, taking into account molecular and Knudsen diffusion. The effective pore size is the diameter of the maximum circumference, which can be inscribed in a flat pore cross section. In this case, the plane section of the pore can have an arbitrary geometric shape. Efficiency of the catalyst is the number of mol of the formed products referred to one mol of the active centers of the catalyst. It is the cumulative characteristic of catalytic properties considering activity, selectivity and period of operation of the catalyst without loss of catalytic activity. Einstein is one mole of photons. This is a widely used unit that is not a SI unit. Elastomers are polymers characterized by highly elastic properties under normal conditions, that is, they can be reversibly deformed. Electrocatalysis is a change in the rate or direction of an electrochemical reaction, depending on the electrode material. The electrode material has a catalytic effect on the reaction rate through the chemisorption steps of various particles on the electrode surface. For example, the speed of electrode allocation of H2 increases by 1,010 times when replacing an electrode from lead by an electrode from platinum. In electrochemical oxidation of alkanes to CO2 which represents a complex chain of intermediate stages with a rupture of C-C and S-N links the electrode can participate in dehydrogenation of chemisorbed fragments and influence the selectivity of some stages. Electrocatalysis is not possible if the electrode material is included in the general electrochemical equation of the process. Example: for anodic copper dissolution Cu0 → Cu2+ + 2e-), or the electrochemical process proceeds without the chemisorption stage at the electrode. The electronic theory of a catalysis is the theory of a catalysis which connects catalytic action to features of electronic (zonal) structure of catalytic agents (metals, semiconductors, dielectrics). Transfer of charges between the reacting molecule and the catalytic agent influences chemisorption strength of reagents.

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Electrophilic catalysis is a catalytic reaction in which the catalyst is a Lewis acid. Example: Friedel-Crafts alkylation in the presence of aluminum chloride AlCl3. Emulsion polymerization is the polymerization of an emulsion of monomer (droplets of monomer or its solution, immiscible with medium, usually water) stabilized by the surfactants (S) with formation of polymeric suspension, that is a suspension of solid substance in the liquid medium. The initiator of the monomer is soluble in water. Process of growth of a chain of polymer goes in micelles surfactant. Enzymes are protein macromolecules that are catalysts in living organisms. Enzymes have unique catalytic properties – they have high activity, are highly specific to reagents, are capable of performing stereo- and regioselective processes with 100% yield. Enzymatic catalysis means catalytic reactions, carried out under the influence of specific biological catalysts – enzymes. Catalytic reactions involving enzymes ensure the vital activity of biological organisms. Also, enzymatic catalysis is widely used in the chemical industry, for example, in the production of glucose from starch, in the synthesis of amino acids, vitamins and other substances. Ethylenediaminetetraacetic acid (EDTA), (HOOCCH2)2N(CH2)2N(CH2COOH)2 is a tetrabasic carboxylic acid, complexone II, white fine crystalline powder, slightly soluble in water, insoluble in most organic solvents, soluble in alkalis, with cations of metals forms salts of ethylenediaminetetraacetate. EDTA is used in the form of disodium salt dihydrate – complex III – in textile, leather, paper, paint and varnish industry, in the production of metals, rubber, in color film industry, for water softening. In analytical chemistry with the help of EDTA determine more than 60 elements. In medicine, EDTA uses for the removal of radioactive and toxic metals from the body, as well as for preserving blood. The excited state is a state with the energy exceeding energy of the main condition of a chemical object. In photochemistry it can be the electronic excited state. The photogenerated free electrons in a zone of conductivity and the free photogenerated holes in a valent zone are the excited condition of the photocatalyst. Free and bound excitons also represent an excited state of the photocatalyst. The active state of the photocatalytic (photoadsorption) center is the excited state of the photocatalyst. At the same time, this state is in its lowest energy state with respect to the set of possible electronic states in the solid subsystem (for example, empty defects and carriers). Exciton is the electronic excitement considered as quasi-particles which are capable to migration. For the description of organic materials use two models: zonal or wave (low temperature, high crystal order) and hopping (higher temperature, low crystal order or amorphous state). In the hopping model, the energy transfer coincides with the migration energy. In semiconductors and insulators, a free electron-hole pair (neutral quasi-particle) is a free exciton, capable of migrating and transferring its energy to the lattice of a solid. The exciton localized is the exciton taken by defect or self-taken by the center in a regular lattice because of its polarization that leads to the electronic excited condition of defect or the localized excitement of a regular lattice respectively. In the latter case, the decay of the exciton can lead to the formation of new defects. The

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decay of a self-trapped exciton on a surface can lead to the formation of surface active centers with catalytic activity. Explosives are chemical compounds or mixtures of chemical compounds that are capable of rapid transformation with the release of a large amount of heat and the formation of gaseous products that, when heated to a high temperature, create high pressure. The composition of explosives is divided into two groups: individual compounds and mixtures. The first group includes polynitrocompounds of the aromatic series and their derivatives (trinitrotoluene, trinitrophenol, trinitroxylols, etc.), nitroamines, nitric acid esters, as well as polyhydric alcohols and carbohydrates (nitroglycerin, nitrocellulose, or pyroxylin, etc.), salts of nitric, rattlesnake H-O-N=C, nitrous acid, etc. The second group includes explosive mixtures: gunpowder, nitroglycerin mixtures – dynamite, ammonium-salt mixture (ammonites, ammonals, etc.). External diffusion regime is a mode of catalytic reaction, in which the rate of the process is limited by the diffusion of matter from the volume of the reaction mixture to the surface of the heterogeneous catalyst. The concentration of reagents on the surface of the catalyst can approach zero. The apparent activation energy of the entire process is determined by the activation energy of diffusion in the volume and is usually ~ 10 kJ/mol. The external diffusion regime is used for a small number of industrial processes, for example, in the oxidation of methanol to formaldehyde on a silver catalyst. External surface is an external surface of particles of catalysts and adsorbents without their internal porous structure (an internal surface). Usually, superficial pores and cavities are also referred to the external surface if their width exceeds the depth. Extrudate is a product obtained by extrusion. Extrusion is a forming method in which a paste is extruded through a spinneret. The size of the holes in the spinneret determines the size and shape of the resulting particles. The quality of the product (extrudate) depends to a large degree on the water content and rheological properties in the initial paste, which are regulated by special additives. F Feedstock is stock from which material is taken to be fed (charged) into a processing unit. The Fermi level is the level associated with the energy of the electrons that are least firmly held in the solid body. The value of the Fermi level at a temperature of 0 K is Fermi energy and is constant for each solid. The Fermi level changes when the solid is heated and when electrons are added or removed. At nonzero temperatures, as the Fermi level, one can select a level that is filled exactly by half in the statistical distribution of the Fermi-Dirac probabilities. Doping of the initial substance leads to a shift in the Fermi level and, consequently, to a change in its energy. The Fischer-Tropsch process is a catalytic process for the production of liquid hydrocarbons from synthesis gas. Metal catalysts containing iron and cobalt are generally used. Due to exhaustion of world reserves of hydrocarbonic raw materials this process was of particular importance for production of synthetic fuels and lubricant coal oils.

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The fixed catalyst is an immobilized catalyst in which the active site is attached to the carrier by a covalent chemical bond. Typically, this term refers to systems in which the surface functional group of a carrier is covalently bound to one of the ligands in the organometallic complex. Such a system retains the properties inherent in free metal complexes in solution, including, for example, the mechanism of catalytic conversion. The advantage of fixed catalysts compared with metal complexes in solution is the possibility to separate the catalyst from the reaction mixture by filtration. Flashing is the process in which a heated oil under pressure is suddenly vaporized in a tower by reducing pressure. Flash point is the lowest temperature at which a petroleum product will give off sufficient vapor so that the vapor-air mixture above the surface of the liquid will propagate a flame away from the source of ignition. The flowing and circulating reactor is the reactor used in laboratory researches in which the catalyst is in a circulating contour with rapid circulation of reactionary mixture through the catalyst. Reagents with a constant speed are entered into a contour, and products with a constant speed are taken away from a contour. Due to rapid circulation of mixture on a contour a number of advantages is reached (constant temperature is established, influence of external diffusion, etc. is eliminated). The flowing reactor is the reactor of continuous action having a constant stream of reagents on an entrance to the reactor and a constant stream of products at the exit from the reactor. The fluidized bed is a method widely used in industry for calcining the solids of ores, pyrite, coal, etc., consisting in blowing air through a layer of granular material in the furnace so that the grains are in a suspended state, as a result of which the volume of the material increases significantly, and the material particles move relative to each other, as in a boiling liquid. The fluidized bed reactor is a reactor in which solid catalyst particles (0.01-0.1 mm in size) are suspended in an upward flow of gaseous reactants. It is a reactor containing a gas, liquid, and a solid phase.The advantages of this type of reactor are the intensive heat exchange between the catalyst particles, the absence of external diffusion inhibition, and the ease of catalyst loading. The lack of a fluidized bed is an increased abrasion of the catalyst particles. Reactors of this type are suitable for reactions with very high heat release, or in cases where the catalyst needs frequent replacement. Fluorene (o, o’-diphenylmethane) is a polycyclic aromatic hydrocarbon. Fluorene is a colorless crystal that is capable of fluorescence when exposed to ultraviolet radiation. It is insoluble in water, but it dissolves well in diethyl ether, it is poorly soluble in ethanol. It is easily oxidized to position 9: oxygen of air to 9hydroperoxyfluorene, under the action of strong oxidants – to fluorenone. Under the action of reducing agents (iodine hydrogen, red phosphorus) forms perhydrofluorene. Fluorene forms a carbanion at the 9-position, in particular, is condensed with aromatic amines to form 9-arylidenfluorenes, when heated with metallic sodium or sodium amide, a 9-sodium fluorene derivative is formed. Fluorene also enters the electrophilic substitution reaction, replacing the hydrogen atom mainly in positions 2 and 7, then at position 4. Fluorene found in coal tar (1.3-2.0%), of which the composition is released in anthracene fraction by crystallization followed by recrystallization from

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gasoline. The laboratory synthesis of fluorene is the pyrolysis of acetylene or diphenylmethane. Fluorene serves as the starting reagent for a number of fluorene dyes. It is also used as a stabilizer of polymers, and also as a monomer. Monocrystals of fluorene are used in scintillation counters. Flux is lighter petroleum used to fluidize heavier residual so that it can be pumped. Forming is a stage of preparation of catalysts which is responsible for the external sizes and a form of particles of the ready catalyst. Forming can be carried out by various methods (spray drying, extrusion, tabletting, granulation, etc.). Fouling is an accumulation of deposits in condensers, exchangers, etc. Fraction is one of the portions of fractional distillation having a restricted boiling range. Fraction С2+ is a mixture of hydrocarbons with the number of carbon atoms from 2 and above. Most often, this term means light hydrocarbons with a carbon number of up to 5. Fractional crystallization is a method of separation and purification of substances, based on the preferential transition of one of the components into a solid phase (precipitate) during crystallization of the solution and the melt. Fractional crystallization is a laborious process, formerly the only methods of separating chemically close substances, for example, Zr and Hf, Nb and Ta, etc. At present, fractional crystallization is very rarely used. Fractional precipitation is a method for separating a mixture of substances that are close in chemical properties and solubility; consists in the consecutive transfer of the components of the mixture into the sediment in separate portions (fractions) as a result of the formation of poorly soluble substances with the added reagent. Fractionating column is a process unit that separates various fractions of petroleum by simple distillation, with the column tapped at various levels to separate and remove fractions according to their boiling ranges. A free-dispersing system is a dispersed system in which the particles of a dispersed phase freely participate in Brownian motion, for example sol. Free electrons are photoexcited electrons passing from the valence band to the conduction band in semiconductors and insulators. Thermoexcitation or doping with certain impurities also leads to the formation of free electrons in the conduction band of semiconductors. In metals and n-type semiconductors the free electrons exist initially. Fuel Gas is refinery gas used for heating. Fundamental absorption (internal absorption) is absorption of ultraviolet, visible or infrared radiation in semiconductors and insulators, which causes optical transitions of electrons, which occur solely because of transitions from the valence band to the conduction band, with the formation of free electron-hole pairs and/or exciton absorption bands. G Gas is a natural mixture of hydrocarbon, non-hydrocarbon compounds and elements that are in formation conditions in the gaseous phase, or dissolved in oil or water conditions, and under standard conditions – only in the gaseous phase.

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The gas cap is the accumulation of free oil gas in the most elevated part of the oil reservoir above the oil deposit. Gas condensate – this term means liquid hydrocarbons of various structures, which are in situ in a gaseous state and are mixed with the natural gas condensate fields. When extracted, they condense and become liquid. During processing, the gas condensate must be stabilized, that is, the dissolved light hydrocarbons-propane, butane, etc., must be removed from it. The gas field – one or several gas deposits, confined territorially to one area, or associated with a favorable tectonic structure (anticlinal fold, dome, etc.) or other type of trap. Gas factor is the amount of natural gas (in cubic meters) per 1t or 1m3 of oil. Gas flow is the amount of gas in volume or weight terms, released from a well or from any source per unit of time (per hour, per day, etc.). Gas fractionation is a process for separating gas mixtures (for example, BFLH) into their individual hydrocarbons or narrower mixtures to produce liquefied hydrocarbon gases. A gas fractionation unit (GFU) is used to separate mixtures of light hydrocarbons into individual components or narrower mixtures – liquefied hydrocarbon gases. Gas-condensate deposit is a deposit in which hydrocarbons in the conditions of the existing reservoir pressure and temperature are in gaseous state. At pressure decrease and temperatures the phenomenon of the so-called "return condensation" at which hydrocarbons partially pass into a liquid phase takes place and remain in pore channels of layer from which it is difficult to extract. The operation of the gas condensate deposit in order to avoid these losses must be done with maintaining the pressure above the reverse condensation point, for which the injection of extracted gas back into the formation after its topping is organized. Gas mode (dissolved gas mode) is the mode of operation of the oil deposit in which oil is entrained to the bottom of the wells by the more mobile masses of the expanding gas that has passed when the pressure in the reservoir decreases below the saturation pressure from the dissolved state to the free state. Gas oil is middle-distillate petroleum fraction with a boiling range of about 175 – 400ºC, usually includes diesel fuel, kerosene, heating oil, and light fuel oil. Gasolines are colorless or yellowish transparent liquids, a mixture of light saturated (C5-C9), aromatic and naphthenic hydrocarbons. Gasoline is a blend of naphthas and other refinery products with sufficiently high octane and other desirable characteristics to be suitable for use as fuel in internal combustion engines. The raw material for the production of gasoline is oil. Motor gasolines also contain unsaturated hydrocarbons. To improve the antiknock properties of gasolines, isoparaffinic and aromatic hydrocarbons and antiknock additives – tetraethyl lead are added to them. Gasoline is used as a motor fuel and as a solvent. Extraction gasoline is used for extraction of vegetable oils, for dry cleaning of tissues, washing of machine parts, as well as for obtaining quick-drying varnishes and paints. Gas processing plant (GPP) is an enterprise where drying, desulfurization (removal of sulfur compounds) and separation of associated oil or natural gas into components – methane and other hydrocarbons takes place.

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The gas-oil reservoir is a reservoir in which free gas occupies the entire higher part of the structure and is directly in contact with oil occupying a reduced part of the structure in the form of a rim, and the volume of the oil part of the deposit is much smaller than the volume of the gas cap. At a large depth of bedding, the gas cap, regardless of its size, may contain petroleum hydrocarbons in the gas-condensate state. The gas saturation pressure is a pressure at which a certain volume of gas is in a dissolved state in the oil. Gel is a structured disperse system in which particles of a dispersed phase (polymer molecules or micelles) form a three-dimensional framework. The gaps in the frame are filled with a liquid dispersion medium. One of the ways of gel formation is coagulation and subsequent coalescence of the sol. General acid-base catalysis is a catalytic reaction which speed is proportional to concentration of acid or the basis in undissociated form. Such regularity is observed in case the limiting stage is transfer of a proton of H+ or OH- hydroxide ion to a reagent molecule. The germ is the smallest particle of a new phase of matter that is formed during crystallization, condensation, and other processes in disperse systems. As a rule, the formation of germ occurs from the metastable state of the initial system. Gram-atom (g-atom) is the number of grams of the element, equal to its atomic mass. For example, the atomic weight of aluminum is 26.98154, the gram-atom of aluminum is 26.98154 g. In technical calculations, a kilogram- and ton-atoms are also used. Gram-equivalent (g-equ) – the number of grams of a chemical element or compound equal to the equivalent mass, i.e., the amount that corresponds to 1 g hydrogen atom or 0.5 g oxygen atom in the compounds or in the reactions. Practically, the gram-equivalent of an element is equal to its atomic mass divided by the valence in a given compound. For acids and bases, the gram equivalent is equal to the molecular weight divided by basicity. Gram-molecular volume is the volume of 1 mole of any gas under normal conditions (0ºC and 760 mm Hg). Practically equal to 22.4 liters. Gram-molecule (g-mol, mole) is the number of grams of a substance equal to the molecular weight of this substance. For example, the molecular weight of H2SO4 98.082 means that one gram molecule of H2SO4 is 98.082 g. In technical calculations, also kilogram- and ton-mole are used. Granules are the substances in the form of unbound particles with a size of more than 1 mm. Granulation is a method for forming granules from powders. Usually, this procedure is performed when the powder is moistened in a rotating drum. Grafting is the formation of a covalent chemical bond between a metal center and a functional group on the surface of a carrier. Usually this term refers to fixed metal complexes in which the functional group of the carrier enters the internal coordination sphere of the metal. This leads to a change in such properties as the symmetry, coordination number, degree of oxidation of the central atom in comparison with the free metal complex in solution. Graphene is the first known truly two-dimensional crystal. Unlike earlier attempts to create two-dimensional conductive layers, for example, two-dimensional

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electron gas, from semiconductors by controlling the width of the forbidden band, electrons in graphene are much more localized in the plane. Graphene is a twodimensional material whose sp2-hybridized carbon atoms form a hexagonal lattice with a C-C bond length of 0.142 nm. The variety of chemical and physical properties is due to the crystal structure and π-electrons of the carbon atoms that make up graphene. A wide study of the material in universities and research laboratories is primarily due to the availability and simplicity of its preparation using mechanical splitting of graphite crystals. Graphene is used in the creation of transparent electrodes, photodetectors, chemical sensors, etc. Having a high specific surface area of 800-900 m2/g, it can also be used to create new catalysts for organic synthesis reactions. H The heat of adsorption is the thermal effect observed during adsorption. The magnitude of the thermal effect gives information on the binding energy of the adsorbent-adsorbate. In some cases, the heat of adsorption strongly depends on the degree of filling of the surface, which is explained by the presence of intermolecular interactions and inhomogeneity of adsorption centers. The thermal adsorption effect can be directly measured with a calorimeter, or calculated from the adsorption isotherms measured at different temperatures. There are isosteric, integral and differential heat of adsorption. Heat exchanger is the equipment to transfer heat between two flowing streams of different temperatures. Heat is transferred between liquids or liquids and gases through a tubular wall. Heparin is an acidic aminopolysaccharide that retards blood clotting; in small amounts, heparin is found in the liver, lungs, spleen, and also in the blood. Isolate heparin in the form of its sodium salt from the lungs and liver of cattle. Apply heparin to reduce blood coagulability, to prevent myocardial infarction of the heart, as a stabilizer in blood transfusion. Herbicides (Latin herba – grass, caedo – kill) – chemical means of control of weeds. According to the nature of the action on plants, herbicides are divided into: continuous action, killing all plant species, and selective, acting on certain plants and safe for others, but depending on the norm and the concentration of herbicides used, the selective ones can also manifest themselves as herbicides are divided into subgroups according to from the nature of the action: contact, root and systemic. The heterogeneity of the centers is the presence of adsorption centers or active centers in the structure of the catalyst with different properties. For example, there is often a different heat of adsorption, a different strength of acid sites, etc. Heterogeneous catalysis is a phenomenon of the change in the rates of chemical reactions under the influence of catalysts, which form a separate phase, while the reagents are in a different phase. The reactants are contacted with the catalyst at the interface. The most widespread systems are those in which reactants from a liquid or gaseous phase interact with a solid catalyst. The heterogeneous catalyst is a catalyst existing in the reaction mixture as a separate phase. A catalytic reaction involving a heterogeneous catalyst necessarily

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takes place at the phase boundary. Unlike a homogeneous catalyst, the advantage of a heterogeneous catalyst is the ease of separating the reaction products from the catalyst. Heterolytic adsorption – the term applied to the dissociative chemical adsorption means heterolytic bond cleavage in the original molecule adsorbed to form the anion and cation. Hexamethylenebenzamide (hexamide) C13H17NO are colorless crystals without a smell, melting point 360ºC; insoluble in water, soluble in most organic solvents, resistant to sunlight. Hexamethylenebenzamide is prepared by reacting hexamethyleneimine with C6H5COCl. It is harmless to humans and animals. Getting on the mucous membrane of the eyes, causes flushing. Hexamethylenebenzamide has a repulsive activity against the louse, repels mosquitoes at 16 ppm, spraying with an aqueous emulsion of hexamethylenebenzamide. Animal protects them from mosquito bites and horseflies for 3 days. The tissue impregnated with hexamethylenebenzamide deters fleas for more than 5 months. Hexamethylenediamine (CH2)6(NH2)2 are colorless glistening crystals with m.p. 42ºC; easily soluble in water and organic solvents, on air smokes, absorbs carbon dioxide, forming a hexamethylenediamine carbonate with inorganic and organic acids forms salts. With dibasic acids, aldehydes and ketones comes on heating in a condensation and polycondensation reaction. The salts of hexamethylenediamine with organic acids, when heated, give the corresponding amides, for example, with adipic acid, a valuable polymeric amide (polyamide) nylon is formed. Hexamethylenediamine is prepared by reducing the adipic acid dinitrile NC-(CH2)4CN with hydrogen over the catalyst (Cu, Co, Ni) and other methods. Hexogen (cyclotrimethylenetrinyroamine) C3H6N6O6 is an explosive; more powerful and sensitive to detonation than TNT, picric acid and tetryl; colorless crystals, melting point 204ºC, insoluble in water, poorly soluble in most organic solvents, flash point of about 230º C. Hexogen is obtained by nitration of urotropine with concentrated HNO3. Applied for the manufacture of detonators, ammunition and explosive work in industry, mainly in a mixture with other explosives. High-line or high-pressure gas is high-pressure (100 psi) gas from cracking unit distillate drums that is compressed and combined with low-line gas as gas absorption feedstock. Highly elastic state is a physical state into which passes solid polymer when heating. It is characterized by ability of polymer in such state reversibly to be deformed when imposing small loading. Homogeneous heterogeneous catalysis is a special type of catalytic processes in which a solid catalyst is capable of initiating a chemical reaction in the bulk phase (in a liquid or in a gas). Examples of processes: oxidation of methane on oxide catalysts at not too high temperatures. Homogeneous catalysis is a phenomenon of changes in the rates of chemical reactions under the influence of catalyst substances that are present in one phase with reagents and are dispersed in this phase at the molecular level. Homogeneous catalysis is possible in the gas phase or in the liquid phase, however, only liquid-phase catalytic reactions are of practical use. Therefore, the term homogeneous catalysis is often used in a narrower sense to refer to reactions in liquid solutions involving soluble catalysts. A homogeneous catalyst is a catalyst that is present in a single phase with reagents and is dispersed in this phase at the molecular level. For example, the

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catalytically active substance can be dissolved in the liquid phase together with the reagents, or it can be present as a gaseous compound in the gas mixture with the reagents. Advantage of the homogeneous catalyst in comparison with the heterogeneous catalyst is the one-type interaction with reagent molecules throughout the volume of reactionary mixture, and the main shortcoming – difficulty of separation of products of reaction from the catalyst. Homolytic adsorption – the term is applied to dissociative chemical adsorption, means homolytic breaking of the bond in the initial molecule with the formation of two adsorbed (surface) radicals. Example: the adsorption of hydrogen to form two radicals H⋅ on the surface of metals. Homogeneous photocatalysis is photocatalysis occurring in homogeneous systems. Hydrazine (diamide) H2N-NH2 is a colorless hygroscopic liquid, boiling point 113.5ºC, hydrazine very actively absorbs water vapor from the air, forming hydrazine hydrate N2H4 · H2O; when carbon dioxide is absorbed, hydrazine carbonate is formed. Hydrazine is a strong reducing agent, it has a large amount of organic derivatives. Hydrazine salts are colorless, readily soluble in water. The most important of them: hydrazine sulfate N2H4·H2SO4, hydrazine hydrochloride N2H4 · 2HCl and N2H4 · HCl. Hydrazine is obtained by oxidation of dilute aqueous solutions of NH3 or carbamide with hypochlorite. Hydrazine is used in organic synthesis, in the production of plastics, rubber, insecticides, explosives, as a component of jet fuel, in analytical chemistry. Hydrazine and all its derivatives are poisonous. Hydrocracking is a catalytic process, the cracking of heavy hydrocarbons in the presence of hydrogen H2. A process used to convert heavier feedstock into lowerboiling, higher-value products. The process employs high pressure, high temperature, a catalyst, and hydrogen. In addition to cracking reactions, hydrogenolysis, hydrogenation of aromatic hydrocarbons, the opening of cycles in naphthenes, hydrodealkylation of alkylaromatic compounds and naphthenes occur. Hydrocracking catalysts can be oxides and sulphides of Ni, Co and Mo. Hydrodearomatization of petroleum fractions is the catalytic processes of hydrogenation of arenes (mainly polycyclic, and also monocyclic) contained in jet and rocket fuels. This is a direct hydrogenation of aromatic hydrocarbons, which are mainly represented by benzene and naphthalene derivatives. Lowering arene content increases the thermal stability of the fuel and reduces the formation of coke during its combustion. Industrial applications in processes of oil fractions hydrodearomatization the oxide and sulfide catalysts were received. Hydrodearomatization of oil fractions is carried out at a temperature of 340-380°C. The content of arenes in fuel is reduced from 20-22% by wt. to 15-16% with shallow hydrodearomatization of oil fractions and up to 5-8% with deep hydrodearomatization of oil fractions; the amount of sulfur, nitrogen- and oxygen-containing compounds (resins) decreases 2-3 times (up to 2-4 mg per 0.1 dm3); the hydrogenation yield is 96-97% by weight. Hydrogenation (latin hydrogenium – hydrogen) is a reaction of hydrogen addition to compounds and elements, occurring in most cases in the presence of catalysts, under pressure and at high temperatures. The reaction of the removal of hydrogen from the compounds is called dehydrogenation. Hydrogenation is widely used in industry for carrying out important chemical and technological processes; syntheses of ammonia, methanol and other alcohols. Hydrogenation of vegetable oils

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produces solid fats, salomas, margarine; from coal, oil products and hot shale – motor fuels and other valuable products. Hydrodesulfurization is a catalytic process of the removal of sulfur from oil or its fractions by hydrogenation of sulfur-containing compounds to form hydrogen sulfide and convert to hydrocarbons and H2S. The process is carried out in the presence of hydrogen H2. The catalysts are supported oxides of Co and Mo, which under the process conditions become sulfides. Hydrogenation is the chemical addition of hydrogen to a material in the presence of a catalyst. Hydrogenolysis is a catalytic process of rupture of C-C or C-X bonds (X = N, S, O, etc.) in hydrocarbons under the action of hydrogen H2. It is carried out on catalysts of hydrogenation and dehydrogenation (for example, metal catalysts). Often, the hydrogenolysis reaction requires high temperatures and a strong binding of the reactants to the catalyst and is therefore difficult to implement. Hydrofinishing is a catalytic treating process carried out in the presence of hydrogen to improve the properties of low viscosity-index naphthenic and medium viscosity-index naphthenic oils. It is also applied to paraffin waxes and microcrystalline waxes for the removal of undesirable components. This process consumes hydrogen and is used in lieu of acid treating. Hydroforming is a catalytic reforming of naphtha at elevated temperatures and moderate pressures in the presence of hydrogen to form high-octane aromatics for motor fuel or chemical manufacture. This process results in a net production of hydrogen and has rendered thermal reforming somewhat obsolete. It represents the total effect of numerous simultaneous reactions such as cracking, polymerization, dehydrogenation, and isomerization. Hydroformylation is a catalytic process, the reaction of an olefin with carbon monoxide CO and hydrogen H2 to form aldehydes of a branched and unbranched structure. Cobalt carbonyl Co2(CO)8, as well as phosphine complexes of cobalt and rhodium, are used as catalysts. Hydrothermal synthesis is a method of obtaining carriers and catalysts in aqueous solutions at temperatures above 100°C and pressures above 1 atm. Under such conditions, water can dissolve many substances (oxides, silicates, sulfides), which under normal conditions are practically insoluble. Advantages of the method are the ability to synthesize large crystals of high quality, as well as the possibility of obtaining crystals of substances that are unstable near the melting point. The main parameters of hydrothermal synthesis are the initial pH of the medium, the duration and temperature of the synthesis, the amount of pressure in the system. I The ideal displacement reactor is a fixed-bed flow reactor in which there is no diffusion stirring of the reaction mixture when passing all length of the reactor. The ideal displacement condition means that in the cross section of the reactor all particles of the reaction mixture move with the same velocity, directed along the flow axis. Thus, all of the reagent molecules have the same contact time with the catalyst. The ideal mixing reactor is a reactor in which the reaction mixture is stirred intensively, and as a result, it can be assumed that the temperature and concentration

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of the substances in the entire reaction volume remain constant. Conditions close to ideal mixing can be realized both in flowing reactors, and in reactors of periodic action. The Ili-Ridil mechanism is a mechanism of a heterogeneous catalytic reaction, in which the compound adsorbed on the surface of a solid catalyst reacts with a molecule from the gas or liquid phase. The immobilized catalyst is a heterogeneous catalyst obtained by applying (putting) a homogeneous catalyst (often a metal-complex compound or enzyme) onto the surface of a solid-phase carrier. The immobilized catalysts have high activity and selectivity characteristic of homogeneous catalysts, and at the same time can be easily separated from the reaction medium, which is an advantage of heterogeneous catalysts. The fixing of homogeneous catalysts on a carrier can be achieved in various ways: through adsorption, non-covalent interactions (ionic or hydrogen bonds), the formation of a covalent bond with a carrier (fixed catalyst), grafting. Impregnation is a method of producing supported (deposited) catalysts, which consists in converting the predecessor of the active component from the solution to the carrier surface. When the substance is applied from the solution, adsorption on the carrier surface, ion exchange or chemical interaction with surface functional groups is possible. It is also possible that there is no specific interaction between the substance from the solution and the carrier, and in this case the deposited material is deposited in the pores of the carrier during the drying of the catalyst. Impregnation on a moisture capacity is an impregnation method in which the volume of impregnating solution is equal to the free volume of the carrier pores (a carrier moisture capacity). Thus, all entered predecessor of an active component appears in the carrier pores. The free volume of the carrier pores can be known in advance, or it is determined in the empirical way or by appearance of granules of the carrier during impregnation. Impurities are substances that are present in small (trace) amounts in the feed, or in the catalyst. Usually this term implies that within the developed chemical technology it is difficult to control the composition of these substances and their quantity. The inhibitor is a substance that slows down the chemical reaction. This term is applied to any reactions (catalytic, non-catalytic, chain). Sometimes for such substances the term negative catalyst is used, which is not recommended by IUPAC rules. The effect of inhibitors can be due to a variety of mechanisms. For example, some inhibitors are irreversibly consumed during the reaction. In case of enzymatic reactions chemical linkng of inhibitor with enzyme is the frequent reason of delay of reaction. This term also means an additive used to prevent or retard undesirable changes in the quality of the product, or in the condition of the equipment in which the product is used. Index group is a part of atoms of the reacting molecule which directly interacts with the surface of the catalyst at adsorption. The induction period is the initial stage of the chemical transformation, during which an increase in the reaction rate is observed (self-acceleration of the reaction). The induction period can be observed in catalytic processes due to various factors (for example, autocatalysis, heating of the system in the case of highly exothermic

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reactions, adsorption of interfering impurities from the reaction mixture onto the catalyst, etc.). Initiating explosives (primary explosives) are compounds that can easily explode from a minor extraneous initial impulse (friction, impact, heating). A distinctive feature of initiating explosives is that their combustion easily passes into detonation, which does not happen with secondary explosives. The initiating explosives are used in military affairs for projectiles, small quantities of which are pressed into thin-walled shells of primer-detonators together with a secondary explosive. The most important initiating explosives are salts of heavy metals of fulminic acid and polynitrophenols, azides, metal acetylides, for example, Ag2C2, etc. The most commonly used are fulminating mercury, lead azide, lead trinitresoresorcinate and tetrozene. In the manufacture of initiating explosives, their preservation and transportation, special care must be taken. Transport initiating explosives can only be transported in the form of ready-made capsules. The initiator of polymerization is a substance that excites polymerization and is irreversibly consumed. Irreversible consumption at the initiation stage distinguishes the initiator from the polymerization catalyst. Example: a peroxide that is readily cleavable to form radicals is used as a radical polymerization initiator. The resulting radicals are embedded in the monomer and thus initiate a chain radical process. Integral selectivity is the ratio of the amount of the target product to the amount of all products obtained during the reaction. The integral heat of adsorption is determined by integrating the differential heat of adsorption for a certain range of values of the degree of filling of the surface. The integrated mode of the reactor is an operating mode of the reactor of ideal replacement at which considerable conversion of initial reagents at the outlet from the reactor is reached. The interface of the phases is the boundary separating the two neighboring phases. Sometimes this term refers to a surface layer thickness of a few atoms, which are different in energy from atoms in the bulk of each phase. For solid particles, this is an external monolayer consisting of a regular matrix of surface atoms (or ions), as well as internal and external surface defects of various types. Internal diffusion is the molecular or Knudsen diffusion of a substance occurring inside granules of a solid porous catalyst. Internal surface is a part of an interface of phases which belongs to pores in particles of the catalyst or adsorbent. Other part of a surface belongs to an external (geometrical) surface of particles. At high porosity the internal surface can considerably (to 106 times) to surpass an external surface in the area. Interphase catalysis is an acceleration of chemical reactions in heterophase systems at addition of a small amount of substance which is called the catalyst of phase transfer. The effect is reached due to acceleration of transfer of molecules between various phases in heterophase systems. The greatest distribution was gained by heterophase systems of type water solution – organic solution or a solid phase – organic solution. The interphase catalysis allows to increase significantly the yield and purity of target products, and also to raise regio-and stereoselectivity of chemical reactions between molecules from different phases. The interphase catalysis is widely used for implementation of nucleophilic and radical-anionic reactions in thin organic synthesis.

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Intradiffusion area is the range of parameters within which the intra-diffusion regime of the reaction proceeds. Intradiffusion mode is the mode of reaction in which the diffusion of reactants in the pores of a heterogeneous catalyst has a significant effect on the rate of the catalytic reaction. Diffusion difficulties lead to a significant concentration gradient within the catalyst granule. At intradiffusion mode, the apparent activation energy is the arithmetic mean value of the true activation energy and the activation energy of the diffusion. Intrakinetic area is the range of parameters within which the intrakinetic mode of course of reaction is carried out. The intra kinetic mode is an implementation of catalytic reaction in conditions when the speed of reaction is small in comparison with the speed of diffusion of reagents in the pores of the solid catalyst. In particles of the heterogeneous catalyst there are no gradients on concentration. At the intrakinetic mode the true kinetic regularities characteristic of this chemical reaction are observed. Intramolecular catalysis is a special type of catalytic reactions when acceleration of chemical reaction in some functional group of a molecule results from catalytic action of other functional group which is in structure of the same molecule. The intrinsic inhomogeneity is the inhomogeneity of the adsorption centers, due solely to the properties of the adsorbent. For example, the strength of chemisorption may depend on the type of crystalline faces present on the surface of the adsorbent. Introduction is a type of reaction in metal complex compounds, when one ligand is built in by the bond between the metal and another ligand. Example: introduction of a CO ligand on a metal-alkyl bond to form an acyl group. Isocyanates are N-isocyanic acid derivatives R-N=C=O, where R can be an aliphatic, aromatic, heterocyclic or organo-organic radical. The most important method of synthesis of isocyanates is the action of phosgene on primary amines or their derivatives – hydrochlorides, carbamates and ureas. The high reactivity of isocyanates is explained by the presence of a system of cumulated bonds –N=C=O, analogous to the system of bonds in ketenes. Isocyanates are used to produce high molecular weight products of polyurethanes and polyureas (condensation of di- and polyisocyanates with polyoxy and poly-amine compounds), widely used by modern techniques to impart water-repellent properties to tissues and skin, for the preparation of adhesives that perfectly connect rubber, metal and fabrics, etc. Many isocyanates are toxic. Isomerization is a catalytic process for obtaining high-octane components of commercial gasoline from low-octane oil fractions. The reaction rearranges the carbon skeleton of a molecule without adding or removing anything from the original material. As a result of the process, linear hydrocarbons are isomerized into branched hydrocarbons. Heterogeneous acid catalysts of various types are used: aluminoplatinum fluorinated catalysts (high-temperature isomerization, 360-440°C), zeolite catalysts (medium-temperature isomerization, 250-300°C); alumina promoted by chlorine, or sulfated zirconium oxide (low-temperature isomerization, 120-180°C). Isomerism is the phenomenon of the existence of compounds that have the same composition (the same molecular formula), but a different structure. Iso-octane is a hydrocarbon molecule (2,2,4-trimethylpentane) with exccellent antiknock characteristics on which the octane number of 100 is based.

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Isostere of adsorption is the dependence of equilibrium pressure of an adsorbtive in a gas phase from temperature measured at an adsorption constant. K Kaolin is a highly dispersed plastic rock, a product of weathering of feldspars, mica, granites; consists of a mineral of kaolinite and various impurities (quartz, mica, feldspar, etc.). Formula: Al2O3·2SiO2·2H2O. Kaolin is used in the production of refractory materials (fire resistance of kaolin 175°C), porcelain, faience and also in paper, rubber, silicate, cable, perfume, and industries. Kerosene is a mixture of hydrocarbons, boiling in the temperature range of 180230º C with direct distillation of petroleum or cracking of petroleum products. Kerosene is a clear, colorless or yellowish liquid with a blue tint. Kerosene is used as a fuel for jet, carburetor tractor engines, for domestic use, as a herbicide. The kinetic mode is implementation of catalytic reaction in conditions when the kinetics of process isn't complicated by diffusion processes (for example, the intra kinetic mode for the heterogeneous catalyst). Knudsen diffusion is the diffusion of gaseous molecules in the pores of a solid, provided that the pore sizes are smaller than the length of a free run of a molecule. This forces molecules to collide more often with the walls of the pore than with other gaseous molecules. In collisions of pores with walls, successive stages of adsorption and desorption of molecules are possible. Knudsen diffusion is characterized by a lower value of the flow of matter compared with molecular diffusion. This is due to the time spent on adsorption of molecules, and diffusion reflection. L Laminar flow is the flow of a liquid or gas, in which particles of matter move in the direction of flow in an orderly and constant linear velocity. An increase in the flow rate or a decrease in the viscosity of the medium can lead to transition of a laminar flow into the turbulent flow. The Langmuir-Hinshelwood mechanism is the mechanism of a heterogeneous catalytic reaction, in which the slowest stage is the reaction between chemisorbed particles. In this case, the adsorption (chemisorption) of the reagents and the desorption of the products are considered as fast equilibrium processes. Leaching is the transition into a solution of one or more components of a solid substance when it interacts with a solvent. The selectivity of the leaching of a particular component is determined by the solubility of the compounds, the chemical properties of the solvent, and the structure of the solid. Lean oil is an absorbent oil fed to absorption towers in which gas is to be stripped. After absorbing the heavy ends from the gas, it becomes fat oil. When the heavy ends are subsequently stripped, the solvent again becomes lean oil. Lewis acid is a substance capable of attaching an electronic pair. Lewis Acid Center (LAC) is a group of atoms in a substance that can attach an electron pair. For example, a coordinatively unsaturated aluminum atom on the surface of Al2O3.

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Lewis's base is the substance capable to give (to donate) electronic pair. The lifetime, τ, is the lifetime of the molecule, which is destroyed by the firstorder kinetics, the time of the molecule concentration decrease by 1/e from its initial value. The lifetime is equal to the reciprocal of the rate constants of the first-order reactions leading to the death of the molecule. Time of life of particles in reactions not of the first order depends on initial concentration of substance. In this case it is called "observed time of life" or "death time". In some cases use the half-decay time which is time of reduction of concentration of substance half from initial. The lifetime of adsorption is the average time during which the molecule is in the adsorbed state and corresponds to the time interval between the collision of the molecule with the surface of the adsorbent and desorption. The limiting stage is the elementary stage in the complex process (consisting of several consecutive stages) which is characterized by the difference of chemical potentials, maximum for process, between the interacting reactionary groups. For simple and quite often for complex chemical processes the limiting stage can coincide with the speed – defining (speed – controlling) stage. The Liquefied Hydrocarbon Gases (LHG) are the hydrocarbonic gases or their mixtures with temperatures of boiling from -50 to 0°C compressed under pressure. The major LHG are propane, butane, isobutane, butylene of various structure and their mixture of different structure. They are made generally from associated petroleum gas, and also at oil refineries. Localized adsorption is an adsorption in which the surface diffusion of adsorbed particles is impossible, or unlikely. This is due to the presence of a high energy barrier for the transition between neighboring adsorption centers. In some cases, localized adsorption leads to the ordering of adsorbate molecules in a two-dimensional lattice. Loosening Molecular Orbitals (LMOs) describe the state of an electron in the disintegration region. In the loosening molecular orbitals, the electron density is concentrated behind the nuclei, and between them it is zero. Low-Line/Low-Pressure Gas is a low-pressure (5 psi) gas from atmospheric and vacuum distillation recovery systems that is collected in the gas plant for compression to higher pressures. Low-temperature condensation is a technological process for processing associated petroleum gas to separate BFLH from a dry stripped gas. The technology is based on the separation of raw materials components with their gradual cooling and condensation: when cooling below -42°C, BFLH components become liquid, and the components of dry gas (methane and ethane) are separated in a gaseous state. M Macrokinetics is the study of kinetic regularities of chemical reactions, under conditions when they are accompanied by heat transfer and mass transfer phenomena. Macropores are the pores with an effective size of more than 50 nm. A massive catalyst is a heterogeneous catalyst, consisting entirely of an active component, for example Raney nickel. Mass transfer is the diffusion of substance or convection resulting from distinction of concentration or electric potentials in the considered initial and final states.

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The mechanism of the chemical process is the set of all intermediates and transition states of the chemical process, which explains the transformation of the initial reagents into final products. The method of Molecular Orbitals (MOs) is the most important method of quantum chemistry. The method is based on the idea that each electron of a molecule is described by its wave function, the molecular orbitals (MOs). Mercury porometry is a method of porosimetry based on the property of liquid mercury not moisten (wet) the majority of solid bodies. The volume of mercury entering the pores is measured, depending on the applied pressure. The method can be used to determine the pore size in a wide range (from 3 nm to 400 μm). Mesopores are pores with an effective size of 2 nm to 50 nm. Methanation is a catalytic process of removing small amounts of carbon monoxide from a gas stream. It leads to the production of methane by the reaction CO + 3H2 → CH4 + H2O. Nickel supported on alumina is used as the catalyst. The process can be carried out at any pressure, typical process temperatures are 200-370°C. Micellar catalysis is an increase in the rate of chemical reactions in the presence of micelles. This term is used even in cases where the acceleration of the reaction is caused by a simple change in the concentration of substances during the transition from solution to micelles. If the structure of micelles contains catalytically active functional groups, acceleration of reaction can be caused by true catalytic process, i.e. intermediate chemical interaction of reagents with the catalyst. Micelles are associates consisting of diphilic molecules (surface-active substances). The diphilic molecule contains a hydrophobic radical and a polar functional group, which determines the characteristic structure of the associates in the aqueous medium (direct micelles) or in a non-aqueous medium (reverse micelles). Micropores are pores with effective size less than 2 nm. The microspherical catalyst is the catalyst in the form of microspheres with a diameter from 20 to 200 microns used in a fluidized bed reactor. The moisture capacity of the carrier is the amount of solvent that is absorbed when the porous system is filled in a pre-dried carrier. Mineralization is the process of complete conversion of organic matter to carbon dioxide, water and other simple inorganic substances, depending on the heteroatom in the starting material. A mixed catalyst is a catalyst consisting of two or more components, each of which is catalytically active with respect to the reaction. Usually, in mixed catalysts, the components are in commensurate amounts. An increase in the activity of such catalysts can be achieved through the interaction of the components with the formation of a new more active phase. Example: iron-molybdenum catalyst for the oxidation of methanol to formaldehyde has the highest activity at a ratio of iron and molybdenum oxides of 1.5: 1 (the phase of iron molybdate is formed). Modifier – this term is used in asymmetric catalysis and means a chiral substance, without which the catalyst can not produce an optically active product. For example, the Raney nickel catalyst is capable of performing asymmetric hydrogenation reactions if an optically active isomer of tartaric acid is present on its surface. The modifying additive – see the promoter.

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Molecular diffusion is a spontaneous process of transfer of substance of area with high concentration to the area with low concentration. Molecular diffusion takes place in gases, liquids, and also when filling of pores of solid substance with gas or liquid if the pore sizes are larger than the length of a free run of a molecule. If the last condition isn't satisfied, so-called Knudsen diffusion is realized. Molecular sieve effect is the effect of the effect of the pore size in the catalyst structure on the selectivity of the catalytic reaction, based on the different availability of the internal space of porous materials for molecules differing in size. A typical example is the catalysis on zeolites and other microporous materials, when the pore sizes are comparable to the dimensions of the molecules. The selectivity of the process may depend on the size of the reagents, products or transition state of the reaction. Example: the cracking process on some zeolites is possible only in normal alkanes. Molecules of a larger size, for example, isoalkanes, are not cracked, as they cannot diffuse to active centers located in narrow pores of the zeolite. Monodisperse – this term is applied to dispersed systems if particles of the same size are present in the dispersed phase. Monolayer adsorption is adsorption, in which all adsorbed molecules directly contact the surface of the adsorbent. Based on the limiting value of monolayer adsorption, the degree of filling of the surface is determined. A monomer is a component of a polymer, its structural unit, a molecule capable of polymerization or polycondensation. Usually contains one (olefins) or two (dienes) double bonds involved in the polymerization. Monomolecular adsorption is an adsorption in which one adsorption center can occupy only one molecule of adsorbate. Monomolecular adsorption reaches a limit when the monolayer is filled and can be described by the Langmuir adsorption theory. The morphology is geometrical features of a structure of solid substances, including a geometrical form and degree of crystallinity of particles of substance, and also a geometrical form of the agglomerates formed of primary particles and the presence in them of porous structure. Multifunctional (polyfunctional) catalysis is a complex difficult multistage catalytic reaction with participation of the multifunctional (polyfunctional) catalyst. Multifunctional (polyfunctional) catalyst is a catalyst containing active centers with different functions. Such catalysts are effective in reactions with several intermediate stages, each of which requires catalytic centers of its own type. Multilayer adsorption is the adsorption, in which several layers of adsorbed molecules are formed. Only molecules from the first adsorption layer interact directly with the surface of the adsorbent, the remaining molecules are adsorbed above the previous layer. N Naphtha is a general term used for low boiling hydrocarbon fractions that are a major component of gasoline. Aliphatic naphtha refers to those naphthas containing less than 0.1% benzene and with carbon numbers from C3 through C16. Aromatic naphthas have carbon numbers from C6 through C16 and contain significant quantities of aromatic hydrocarbons such as benzene (>0.1%), toluene, and xylene.

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Naphthalene is a hydrocarbon of a cyclic series, in the molecule of which there are two condensed benzene nuclei, a solid crystalline substance with a characteristic odor. It does not dissolve in water, but is readily soluble in benzene, ether, alcohol, chloroform. The chemical formula is C10H8. Naphthalene is chemically similar to benzene: it is easily nitrated, sulfonated, reacts with halogens. It differs from benzene in that it is even easier to react. Naphthalene is obtained from coal tar. Also, naphthalene can be isolated from the heavy pyrolysis resin (quenching oil), which is used in pyrolysis on ethylene plants. Another way of industrial production of naphthalene is dealkylation of its alkyl derivatives. In nature, naphthalene is released by termites of the species Coptotermes formosanus to protect its nests from ants, fungi and nematodes. It is used for the synthesis of phthalic anhydride, tetralin, decalin, various derivatives of naphthalene. Naphthalene derivatives are used to produce dyes and explosives, in medicine, as insecticide moths in everyday life. Large single crystals are used as scintillators for recording ionizing radiation. It can be used to create synthetic analogues of cannabinoids. Naphthenes are hydrocarbons (cycloalkanes) with the general formula CnH2n, in which the carbon atoms are arranged to form a ring. Negative catalyst – see inhibitor. Nitrobenzene, C6H6NO2 is a colorless liquid with a sharp smell, reminiscent of the smell of bitter almonds. It’s poisonous. It is insoluble in water. It is distilled with water vapor. Nitrobenzene is produced in enormous quantities to produce aniline, the starting material for the production of various organic compounds. In industry, nitrobenzene is produced by the action of a nitrating mixture (68% and 32%) on benzene at 60°C. Nitration is carried out in the form of a batch or continuous process. The most progressive is the continuous process of nitration in nitrates of column type. Nitrophenols (hydroxynitrobenzenes) are organic compounds, nitro derivatives of phenol, with the general formula HOC6H5-n (NO2)n. Nitromethane is a chemical compound with the formula CH3-NO2. The simplest representative of aliphatic nitro compounds. The main use of nitromethane is as a solvent (for example, ether-cellulose varnishes, vinyl polymers, cyanoacrylates (super-glue), some paints), for the extraction of aromatic hydrocarbons, in the production of chloropicrin, certain explosives. It is used as a jet fuel and as a fuel for racing cars. It is also used as a fuel additive for stale internal combustion engines (for example, in radio-controlled models). Noble metals are gold, silver and metals of the platinum group (ruthenium, rhodium, palladium, osmium, iridium, platinum). Noble metals resistant to corrosion, refractory, poorly soluble in acids, characterized by ductility and ductility, have an attractive appearance. Noble metals are widely used in engineering, jewelry, and laboratory practice. Non-activated adsorption – the term emphasizes that adsorption (or chemisorption) is carried out without an activation barrier, in contrast to activated adsorption. Non-binding molecular orbitals (NBMOs). Electrons located on non-bonding molecular orbitals do not take part in the formation of a chemical bond. Nondissociative adsorption is a variant of chemisorption, in which the adsorbed molecule does not undergo dissociation into fragments, in contrast to dissociative

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adsorption. An example of nondissociative adsorption is the adsorption of CO on metals and oxides. Non-localized adsorption is an adsorption in which adsorbed molecules are able to migrate along the surface of the adsorbent. Unlike localized adsorption, the energy barrier separating neighboring adsorption centers is either absent or insignificant in magnitude. Normal hydrocarbons are hydrocarbons of unbranched, linear structure of the chain. Nucleophilic catalysis is a catalytic reaction in which the catalyst is the Lewis base. Example: hydrolysis of acetic anhydride in an aqueous solution in the presence of pyridine. O Octane number is a measure of the detonation resistance of fuel, that is, the ability of the fuel to withstand self-ignition when compressed in the combustion chamber of a gasoline engine. A number indicating the relative antiknock characteristics of gasoline. The name comes from the fact that in the conventional scale of detonation resistance the number 100 is assigned to a normal octane. Oil (petroleum) is an oily liquid, usually brown to almost black, less often brownish-red to light orange, with a specific odor. It is a mixture of hydrocarbons of methane, naphthenic and aromatic series with an admixture of (usually minor) sulfur, nitrogen and oxygen compounds. The specific gravity is seldom below 0.7 and above 1, fluctuating usually in the range 0.82-0.89. The low specific gravity of oils (light oils) can be due to both their chemical character – the predominant content of methane hydrocarbons and the fractional composition – high content of gasoline. Heavy oils have a high specific gravity due to the high content of asphalt-resinous substances, the predominance of cyclic structures in the structure of hydrocarbons and the low content of easily boiling fractions (the initial boiling point sometimes exceeds 200ºC). The sulfur content of the oils is usually lower than 1%, but sometimes reaches 5 – 5.5%. The amount of paraffins varies from trace amounts to 10% or more. Oil with the high content of paraffin differ in the increased freezing temperatures (it is higher than 0ºC also to + 20ºC), oil with the low content of paraffin stiffen at temperatures sometimes below – 20 ºC. The maintenance of asphalt and resinous components and viscosity of heavy oil, as a rule, above, than that of light oil. Oil-absorption unit is a technological unit intended for the processing of associated petroleum gas – separation of a wide fraction of light hydrocarbons and dry stripped gas. The principle of operation is the difference in the ability of hydrocarbon gases to dissolve in oil media. Components of dry gas (mainly methane, as well as ethane) are not soluble, and components with more than 2 carbon atoms are dissolved. Oil-bearing characteristics – 1) the direct separation of liquid oil, 2) the impregnation of rocks with oil; 3) deposits of solid bitumens (asphalt, ozocerite); 4) release of combustible gas; 5) the presence of mud volcanoes; 6) an oil or bituminous smell emitted by the rock, sometimes only after a strong heating of it; 7) coloring of the gasoline or benzene extract of the determined rock. Oil-bearing characteristics indicate the possible presence of oil in the rocks in the considered rocks of this area.

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Oil-bearing rocks are rocks impregnated with oil. Typically, oil impregnates well-porous rocks – sands, sandstones, fossilized limestones, etc., creating from such rocks the industrial-oil-bearing horizons to be developed. Oil-bearing rocks are also clays, etc., dense rocks, but the oil in them is dispersed and slightly concentrated only in bends and crushed parts. The oil-bearing region is a set of several adjacent genetically linked structures with signs of oil or a set of similar oil deposits with similar oil-bearing suites. Oil recovery is a degree of completeness of oil recovery. Oil reservoir is a layer of rock, more or less impregnated with oil. Oil saturation of layer is amount of the oil which is available in layer in relation to the total volume of pores, cavities and cracks in oil-containing rock. In natural conditions, oil saturates a small part of the pores, and larger ones. Small pores, due to the action of surface tension forces, are occupied by water. The more small pores, the more "buried" water in the layer. In some layers, the amount of this water is quite significant – up to 40%. "Buried" water in the process of exploitation of the reservoir does not usually manifest itself, and the wells give waterless oil. Olefins – it is a family of unsaturated hydrocarbons with one carbon-carbon double bond and the general formula CnH2n. Also see Alkenes. Open pores are channels or cavities that communicate with the outer surface of the particle. Molecules from the surrounding space can freely penetrate into the open pores by diffusion. Ostwald's maturation is the process of increasing the particle size due to the transfer of matter from small particles to larger particles. Such mechanism is implemented in many processes, for example, at coarsening of sols, crystallization of soluble precipitates, increase in the sizes of deposited metal particles. Oxidative addition is a type of ligand binding reaction to a metal complex compound when a metal atom provides electrons to form a bond with a ligand. The initial complex should have two vacant positions in the coordination sphere, and the state of the central metal atom should be stable in oxidation states that differ by two units. In the oxidative addition reaction, many substances (H2, HI, CH3I, etc.) enter. Oxidative dissociative adsorption – this term indicates the direction of transfer of electrons from the adsorbent to the adsorbate during dissociative adsorption. Example: oxidative dissociative adsorption of Cl2 on metals leads to the formation of two surface Cl- ions. P Paraffins – it is a family of saturated aliphatic hydrocarbons (alkanes) with the general formula CnH2n+2. Particle size distribution is the statistical distribution of the number of particles, depending on their size. It is determined by microscopic methods. Passivation is a method of protecting metal catalysts by means of a small controlled oxidation of the surface in an oxygen medium. The resulting oxide layer on the surface of metal particles prevents further oxidation of the metal. Peptization is a process that reverses coagulation, the destruction of aggregates in a dispersed system, for example, the destruction of the gel structure with the formation of sol.

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Petroleum natural gases are gases consisting of a mixture of gaseous hydrocarbons of the paraffin series (СnН2n+2): methane CH4 (sometimes up to 99%), ethane C2H6, propane C3H8, butane C4H10, with an admixture of nitrogen, carbon dioxide, hydrogen sulfide and gasoline vapors. Distinguish dry gas – with a predominance of methane – and fatty gas – with a high content of heavy hydrocarbons. The phase transfer catalyst is a substance that facilitates the acceleration of reactions in heterophase systems by accelerating the transport of molecules between different phases in heterophase systems. For example, ammonium and phosphonium salts (or their organic analogues), as well as crown ethers, aliphatic ethers and other compounds serve as phase transfer catalysts for the most common systems of the type of water-organic solutions. The mechanism of action of the phase transfer catalysts depends on the phase in which the reaction takes place. Example: the process of nucleophilic substitution in alkyl halides proceeding in the organic phase is accelerated in the presence of ammonium cations NH4+, which are capable of transferring the inorganic anion from the aqueous phase to the organic phase. In some cases, the interfacial catalyst increases the solubility of the organic matter in the aqueous phase due to the effect of salting, for example, such an action has NH4+Xsalts during benzoin condensation. Phenanthrene is a tricyclic aromatic hydrocarbon. The chemical formula of C14H10. Phenanthrene is a brilliant, colorless crystals. It does not dissolve in water, it dissolves in organic solvents (diethyl ether, benzene, chloroform, methanol, acetic acid). Phenanthrene solutions fluoresce in blue. According to its chemical properties phenanthrene resembles naphthalene. Contained in coal tar together with its linear isomer anthracene. The derivatives of phenanthrene are widely distributed in living nature (steroids, alkaloids of the morphine group). Fentantren is used in the manufacture of dyes. It is a stabilizer of explosives. Photoadsorption is adsorption, usually chemisorption initiated by ultraviolet, visible or infrared radiation absorbed by adsorbate or adsorbent. Photoadsorption often is considered as primary stage of heterogeneous photocatalytic reaction. However in some cases photocatalytic reaction is initiated not by adsorption on the surface of the photocatalyst. Example: photocatalytic oxidation of the chlorinated hydrocarbons. Photodesorption is a desorption caused by absorption of ultraviolet, visible or infrared radiation by an adsorbate or adsorbent. Photodesorption can be a step in the general mechanism of heterogeneous photocatalysis. Photodesorption is the reverse process of photoadsorption. For a specific system, both processes (or reactions) are caused by ultraviolet, visible or infrared radiation of the same wavelength range. A photoinitiator is an agent that initiates a corresponding chemical transformation under the influence of ultraviolet, visible or infrared radiation, and is spent in this transformation. The photocatalyst can also act as a photoinitiator, but it is not consumed in the chemical transformation. Photoinitiation is photo origination of the free radical, electron-hole pair or the ion capable to initiate chain reaction, for example polymerization, halogenation, and nitrosylation. Photocatalysis is the phenomenon of change of speed of chemical reaction or its initiation under the influence of ultra-violet, visible or infrared radiation in the

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presence of substance − the photocatalyst which absorbs light and participates in chemical transformations. Physical adsorption is adsorption, which is provided by weak physical interactions (usually due to van der Waals forces, dipole interactions, etc.) between adsorbent and adsorbate. Physical adsorption, in contrast to chemical adsorption, is completely reversible and is characterized by low values of Gibbs energy and heat of adsorption. For example, in the physical adsorption of gas molecules, the heat of adsorption often corresponds to the heat of condensation of the vapor into the liquid. The plasticizer is a substance that is introduced into the material to give it plastic properties. Poisoning is a decrease in the activity of the catalyst, which is caused by the interaction of the active sites of the catalyst with the catalytic poison present in the reaction mixture. There are reversible poisoning and irreversible poisoning. In reversible poisoning, the catalytic activity is restored to its original level after removal of the poison from the reaction mixture. In case of irreversible poisoning, for example due to strong adsorption of the poison on the active centers of the catalyst, the catalytic activity remains low even after removal of the poison from the reaction mixture. In this case, the catalytic activity can be recovered by regenerating the catalyst, or by complete chemical processing of the poisoned catalyst. Polydisperse – this term is applied to dispersed systems, if in a dispersed phase there are particles of unequal size. Polyforming is the thermal conversion of naphtha and gas oils into high-quality gasoline at high temperatures and pressure in the presence of recirculated hydrocarbon gases. Polymerization is a chemical reaction (and also a corresponding technological process) for the formation of polymers from constituent parts – monomers. The process of combining two or more unsaturated organic molecules to form a single (heavier) molecule with the same elements (monomers) in the same proportions as in the original molecule. The polymerization catalyst is a substance which excites ionic or coordination and ion polymerization. The role of the catalyst of polymerization consists in creation of the active centers on which growth of molecules of polymer is carried out. The nature of active centers determines the mechanism of the process, the kinetics of the elementary stages of the process, the molecular weight distribution of polymer molecules, and the spatial structure of the polymer formed. Thus, the polymerization catalyst, in contrast to the polymerization initiator, takes part not only in the polymerization excitation stage but also in all subsequent polymer chain growth stages. Polymers are organic substances that are long molecular chains composed of identical fragments – monomers. Polymolecular adsorption is adsorption, in which several adsorbate molecules can be adsorbed on a single adsorption center. For example, the theory of BET adsorption is based on the assumption of polymolecular adsorption. Polynuclear hydroxocomplexes (PGA) are polymer multinucleated complex metal compounds containing bridging bonds of OH-hydroxide-ions. Polynuclear hydroxocomplexes are formed from amorphous and difficult-to-crystallize hydroxides in the process of hydrolysis of metal salts.

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Pollution of the catalyst is blocking of the active centers of the catalyst by the mechanical impurity which is contained in raw materials. In case of the heterogeneous catalyst mechanical impurity can also block porous system in granules of the catalyst and, thus, reduce degree of use of a surface. Pores are cavities (emptiness) or channels in solid particles. It is commonly believed that the depth of the pores exceeds their width. There are open pores and closed pores. Pore size distribution is the statistical distribution of pore volume, depending on their size in the material under study. It is determined experimentally by the results of porosimetry or by calculation methods (by the adsorption isotherm). The pore size distribution affects the diffusion of the reactants and products in the solid-phase catalyst particles. The pore volume is the total volume of all pores present in the solid material. Porometry is the determination of the pore size in a solid. Porometry provides information on the minimum and maximum pore size, the distribution of pores by size, and the average pore size in the sample. The main porometry methods are the adsorption method (pore size from 0.35 to 100 nm) and mercury porosimetry (pore size from 3 nm to 400 μm). Porosity is a share of the free volume which isn't occupied with catalyst granules in a layer from such granules. Porosity is the presence of pores or cavities in the material. Numerically, the porosity is expressed as the ratio of the pore volume in the particle of the substance to the total volume of this particle. Thus, the porosity can vary from 0 (total absence of pores) to ~ 1, and a strict value of 1 is unattainable. In industrial catalysts, the porosity is 0.2-0.8. Porous structure of substance is structure of porous space, i.e. a spatial arrangement and the sizes of pores in substance particles. Post-adsorption is adsorption after preliminary irradiation of the photocatalyst in a vacuum. Precipitation is the process of formation of a solid precipitate in a solution. The precipitation of the solution can be caused by evaporation of the solution, a decrease in the solubility of the substance when the solvent is replaced, a chemical reaction with the transfer of the substance to a less soluble compound. Precipitation is widely used as a sufficiently universal method in the synthesis of various catalysts. For the technology of catalyst preparation, the rate of deposition, temperature and the presence of impurity ions, which may be a catalytic poison, are of great importance. Precipitator is a substance which addition to solution causes formation of a deposit. The added substance can interact with the dissolved substance with formation of insoluble compounds, or change acidity of the medium or polarity of solvent. A precursor is a weak adsorption complex or a special nonequilibrium state of the molecule, preceding the strong chemisorption of this molecule. The predecessor is an initial or intermediate chemical compound which at the subsequent stages of synthesis passes into target substance. Preheater is the exchanger used to heat hydrocarbons before they are fed to a unit. Pressure-regulating valve is a valve that releases or holds process-system pressure (that is, opens or closes) either by preset spring tension or by actuation by a valve controller to assume any desired position between fully open and fully closed.

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Primary particles are particles of the smallest size, which can be identified as independent discrete constituents of the substance. Since the resolution of methods can depend strongly on a particular sample, usually when specifying the primary particles, it is also necessary to indicate the identification method (for example, transmission or scanning electron microscopy). Probability of sticking is probability that the molecule is adsorbed after collision with the surface of adsorbent. The probability of sticking average on all possible impacts happening to different angles and speeds corresponds to sticking coefficient. The production rate of a well is the amount of production that is obtained from a well in a unit of time. Oil always has as its companion the oil gas released from the oil when it leaves the surface. Therefore, distinguish oil production and gas production. Some wells produce oil with water, sometimes in the form of an emulsion. For these wells, the water production rate and the emulsion discharge are distinguished in addition to the oil and gas production rate. In oil field practice, oil, emulsion and water flow rates are usually measured in tons per day, and gas production in cubic meters per day. Sometimes the water flow rate is expressed as a percentage of all the liquid produced by the well. Product yield is the relation of amount of the reagent which has turned into this product to the total of reagent given on a reactor entrance. The amount of reagent can be measured in various units (mol number, weight, etc.). A promoter is a substance added in small amounts to a catalyst in order to improve its activity, selectivity or stability. At the same time, the improvement in the properties of the catalyst is much greater than that which could be obtained as a result of the independent action of the promoter itself. Promoters can be a variety of substances. Distinguish textural promoters (have a physical effect on the catalyst) and structural promoters (change the chemical properties of the catalyst). Propane-propylene fraction is a mixture of gaseous hydrocarbons with the number of carbon atoms 3, formed in the course of catalytic cracking during oil processing. The pulse reactor is a flow reactor operating in a pulsed mode. It is used in laboratory studies to study fast processes. In a pulsed reactor, a carrier gas stream is continuously fed through the catalyst, into which a stream of reagents is periodically added in the form of a short pulse. After each pulse, the reaction products can be analyzed, or the changes that have occurred to the catalyst are studied. Pyrene is a chemical compound with the formula C16H10, polycyclic aromatic hydrocarbon. White crystalline substance. When stored for a long time, it turns yellowish due to the formation of oxidation products. Pyrene is formed as a result of various combustion processes. So, for example, when the internal combustion engine of a car is working, about 1 μg of this compound is formed per 1 km of run. Pyrene is able to be oxidized by the action of chromium salts (VI). It also relatively easily enters the hydrogenation, electrophilic substitution, and Diels-Alder reaction. Applied in the production of naphthalene-1,4,5,8-tetracarboxylic acid, single crystals – for the production of scintillation counters. Pyrene irritates the skin, the respiratory tract and eyes; MAC (MPC) 0.1 mg/m3. Pyrolysis is a thermal process of decomposition of hydrocarbon feedstock to produce ethylene, propylene, benzene, butadiene, hydrogen and a number of other products.

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Pyrolysis gasoline is a by-product from the manufacture of ethylene by steam cracking of hydrocarbon fractions such as naphtha or gas oil. Pyrophoric Iron Sulfide is a substance typically formed inside tanks and processing units by the corrosive interaction of sulfur compounds in the hydrocarbons and the iron and steel in the equipment. On exposure to air (oxygen) it ignites spontaneously. Q Quench oil is oil injected into a product leaving a cracking or reforming heater to lower the temperature and stop the cracking process. R Radiation catalysis is a change in the rate of a chemical reaction under the action of ionizing radiation in the presence of a radiation catalyst. When using ionizing radiation, from vacuum ultraviolet to higher energies, the phenomenon of photocatalysis does not differ from the phenomenon of radiation catalysis. In connection with non-selective absorption of ionizing radiation, it is possible to excite all participants in the reaction (both reagents and catalysts). Thus, the phenomenon designated as "radiation catalysis" includes both direct radiation and catalytic processes. Raffinate is the product resulting from a solvent extraction process and consisting mainly of those components that are least soluble in the solvents. The product recovered from an extraction process is relatively free of aromatics, naphthenes, and other constituents that adversely affect physical parameters. Reaction speed is the number of acts of chemical transformation for a unit of time carried to unit of volume of reactionary mixture (in case of homogeneous reaction) or to surface unit of area (in case of heterogeneous reaction). Reactor is the vessel in which chemical reactions take place during a chemical conversion type of process. Reactive adsorption is dissociative adsorption, in which one molecule fragment is attached to the adsorbent, and the second – to another adsorbed molecule. Reactive desorption is an associative desorption, the reverse process to reactive adsorption. The reactor of periodic action is a hermetically closed capacity where reactionary mixture and the catalyst are placed. After certain time process is stopped for extraction of products. As during process the reactor remains hermetically closed, partial pressure of substances in the reactor can change considerably at course of reactions. The reactor productivity is the quantity of the obtained product in unit of time referred to volume (sometimes to weight) of the reactor. The reactor with the ascending stream of particles of the catalyst is the reactor representing a vertical strut in which from below the two-phase stream from gaseous reagents and solid particles of the catalyst moves up. Usually use a stream with the increased relation of solid substance to gas as gas rises up quicker, than catalyst particles. Reactors of this kind apply, for example, in processes of cracking

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of hydrocarbons on the zeolite catalysts, while the time of contact of reagents with the catalyst makes 5-7 sec. Reboiler is an auxiliary unit of a fractionating column designed to supply additional heat to the lower portion of the column. Recombination – in the case of photocatalysis, the term means the disappearance of free electrons and holes due to the transition of electrons from the conduction band to the valence band. Recombination can also occur as a result of the interaction of trapped electrons and holes or electrons and holes inside the forbidden band or because of the influence of impurities or defects in the crystal structure. The rate of recombination determines the steady-state concentration of nonequilibrium photocarriers in continuously irradiated solid photocatalysts. Thus, recombination determines the rates and quantum yields of most heterogeneous photocatalytic reactions. Rectification is the process and technology of separation of substances based on gradual evaporation and condensation of vapors. Recycle gas is a high hydrogen-content gas returned to a unit for reprocessing. Reduced crude is a residual product remaining after the removal by distillation of an appreciable quantity of the more volatile components of crude oil. Reductive dissociative adsorption is the direction of electron transfer from adsorbate to adsorbent under dissociative adsorption. The refinery is an oil refinery. Refines oil into fuels, oils, and also produces petrochemical raw materials – straight-run gasoline, liquefied gases, propylene, butane-butylene fraction, aromatic compounds, etc. Reflux is the portion of the distillate returned to the fractionating column to assist in attaining better separation into desired fractions. Reformate is an upgraded naphtha resulting from catalytic or thermal reforming. Reforming of gasoline oil fractions is the thermal or catalytic conversion of petroleum naphtha into more volatile products of higher octane number. I.e. it is a process which is carried out to increase the octane number in gasoline fractions with a boiling point of 80-180°C (naphtha). In the process of reforming, alkane molecules undergo rearrangement without changing the number of carbon atoms in the molecule (isomerization, dehydrogenation and dehydrocyclization reactions). So it represents the total effect of numerous simultaneous reactions such as cracking, polymerization, dehydrogenation, and isomerization. Bifunctional catalysts containing active centers of acidic and dehydrogenating type, for example, Pt/Al2O3, are used. Regeneration is the treatment of the deactivated catalyst under conditions other than the reaction one. Regeneration is carried out in order to completely or partially restore the catalytic activity. In a catalytic process it is the reactivation of the catalyst, sometimes done by burning off the coke deposits under carefully controlled conditions of temperature and oxygen content of the regeneration gas stream. A regular surface is the perfect surface of a solid without inhomogeneities and defects. In practice, this term is used to denote local areas of the space of real relaxed and reconstructed surfaces, if it is possible to neglect the indignations caused by the nearby (surface) defects. Relative catalytic activity is a value determined to compare the activity of several catalysts when they interact with a reaction mixture of the same composition. Usually compare time demanded for achievement of the same degree of

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transformation of reactionary mixture on different catalysts. An alternative way is comparison of temperature at which various catalysts give identical conversion at the same time of reaction. The method of relative catalytic activity is applicable for a number of similar catalysts when the mechanism of catalytic reaction doesn't change. The reverse spillover is the transfer of adsorbed particles from the carrier to the active component in the supported (deposited) catalyst as a result of surface diffusion. A rock is a mineral mass of more or less constant composition and structure, usually consisting of several minerals, sometimes from one mineral (for example, gypsum), and is involved in the structure of the earth's crust. The rocks are divided into three large groups according to their origin: magmatic, sedimentary and metamorphic. S Scrubbing is purification of a gas or liquid by washing it in a column. Sedimentary rocks are rocks that are the products of the destruction of any rocks, the vital activity of organisms and the loss of mineral particles from the aquatic or air environment and their subsequent compaction and change – in all cases at the pressure and temperature peculiar to the surface parts of the earth's crust. Self-poisoning is a deactivation of the catalyst in case the product of catalytic reaction is an inhibitor or catalytic poison. Selective chemisorption is a method for determining the surface area of an active component in supported metallic catalysts. The method is based on the selective chemisorption of probe molecules (H2, CO, etc.) on the metal surface. In this case, the conditions are selected so that the probe molecules are not adsorbed on the surface of the carrier. Selective poisoning is a method of increasing the selectivity of a catalyst in the presence of a catalytic poison that has a selective effect on the active centers of the catalyst. Example: selective poisoning of a silver catalyst with halogens results in the complete oxidation reaction of ethylene being suppressed to a greater degree than the formation of ethylene epoxide. Selectivity of the catalyst is the reagent share (in %) which has turned into a target product, to a share of the reacted reagent. It shows degree in which the catalyst is capable to accelerate reaction with formation of a target product instead of the side (undesirable) reaction. Depending on a way of calculation distinguish integrated and differential selectivity. The semiconductor is a material which conductance increases exponentially in case of increase in temperature owing to thermal generation of the free charge carriers under the Van Hoff law. Energy of the forbidden band of the intrinsic semiconductor can be about 2 eV. The intrinsic semiconductor represents material with insignificant defect concentrations and impurity in which thermal excitation leads to interzonal generation both electrons, and holes with identical concentration of both types of carriers. This condition requires small energy of the forbidden band of the semiconductor. In process of growth of crystals these materials are doped by trace quantities of other elements for creation of the areas of n-or p-types.

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The n-type semiconductor is a material in which electrons are the main carriers because of presence of small donor intrinsic defects and/or impurity in a lattice. The p-type semiconductor is a material in which holes are the main carriers due to the presence of small acceptor intrinsic defects and/or impurities in the lattice. The presence of defects and impurities (doping) in n- or p-type semiconductors leads to the appearance of semiconductor properties for materials having a wider forbidden band than for intrinsic semiconductors. For example, ZnO and TiO2 having the forbidden band 3 eV behave as n-type semiconductors. In case of contiguity of the nareas and p-types there is a transition sending current to one side and prevents a reverse current forming the diode. Sibunit is the carbon – carboneous composite material obtained by oxidizing processing of the system consisting of pyrolitic carbon and soot. The variation of the sizes of pores and specific surface area over a wide range is possible. Sibunit finds broad application, including it is used as the carrier for preparation of catalysts. Sintering is an accretion (fusion) of small crystals with formation of agglomerates of various size. At the same time there is a disorder consolidation of structure. At sintering, unlike crystallization, the unstable and disorder structure is formed. Sintering is always followed by simultaneous decrease in specific surface area and volume of pores that leads to irreversible deactivation of the catalyst. Accelerated sintering of catalysts can be caused by overheating in industrial devices. Coked sections on the surface of heterogeneous catalysts also tend to be sintered due to overheating. The size of the pore is the distance between the opposite walls of the pore. The skeleton catalyst is a highly disperse metal catalyst obtained by leaching from alloys. The first step in the preparation of the skeletal catalyst is the preparation of an alloy of the active component with aluminum (or other reactive metal). In the second stage, the aluminum is removed from the alloy by the action of an alkali. This results in the formation of a highly disperse metal phase of the active component. Advantages of skeletal catalysts are high mechanical strength and high thermal conductivity. The most frequently used skeletal catalyst is Raney nickel. Solvent extraction is the separation of materials of different chemical types and solubilities by selective solvent action. Sour gas is natural gas that contains corrosive, sulfur-bearing compounds such as hydrogen sulfide and mercaptans. Specific acid-base catalysis is a catalytic reaction which velocity is proportional to the concentration of protons H+ or hydroxide ions OH-. Such regularity is observed in case transfer of H+ or OH- to a molecule of reagent is carried out quickly and precedes the limiting stage. At the same time the speed of catalytic reaction doesn't depend on nature the catalyst (at constant pH). Specific catalytic activity (SCA) is the catalytic activity per unit surface of a solid phase catalyst. In some cases, the specific catalytic activity is determined per unit surface area of the active component. Specific productivity of the reactor is the amount of product formed per unit time in a unit of reactor volume. This value is often used to compare the efficiency of industrial reactors.

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The specific surface area (specific surface) is the surface area related to the mass of the corresponding phase. As adsorbents and catalysts substances with specific surface area from ~ 10 m2/g to ~ 1,000 m2/g are applied. Specific volume of pores is the volume of pores in a solid, per unit mass. Spillover is a transfer of adsorbed particles from the active component to the carrier. It occurs as a result of surface diffusion of particles formed as a result of dissociative adsorption on the active component. The speed-defining stage is a stage which parameters are included into expression for resultant speed gross – reactions. Sol is a dispersed system formed by particles of a liquid or solid, which are distributed in a liquid or gaseous dispersion medium. The particle size of the dispersed phase is from 1 to 100 nm. The sol-gel method is a method for synthesizing catalysts and adsorbents. Includes a number of consecutive stages: hydrolysis of the starting material in the solution, the formation of low molecular weight complexes and their further conversion to sol, the formation of a gel-like structure of the sol particles, the aging of the gel, the drying of the gel. The advantage of the sol-gel method is the ability to control the composition and microstructure of the porous body at the molecular level, which ensures homogeneity of chemical, physical and morphological properties in the resulting material. Speed (TON) is the number of acts of catalytic transformation at one active center of the catalyst during the catalytic reaction. The number of transformations characterizes the total activity of the catalyst during its entire service life. In photocatalysis, this is the ratio of the number of acts of photoinduced transformations over a certain period of time to the number of active centers or photocatalytic centers in the main state. Spray drying is a method for formation of particles by dispersion of suspension or solution in hot air. Such way allows to replace with one operation stages of filtering, drying and formation, however demands big expenses of energy. Spray drying is used, for example, in the manufacture of a microsphere catalyst. Stabilization is a process for separating the gaseous and more volatile liquid hydrocarbons from crude petroleum or gasoline and leaving a stable (less-volatile) liquid so that it can be handled or stored with less change in composition. Stabilization of condensate is a technological process for the processing of gas condensate, consisting in the isolation of light gases (methane, ethane and a wide fraction of light hydrocarbons) from it to obtain a stable condensate and a number of other products. Stable natural gasoline is a product of gas condensate stabilization. A mixture of liquid hydrocarbons of different structures, which are gasoline-kerosene fractions of petroleum. The stationary mode of catalysis is a method for carrying out a catalytic reaction, in which the properties of the system remain constant in time at each point of the reaction space. Such unchanged properties can be, for example, the composition of the reaction mixture, the reaction rate, the surface state of the catalyst. Typically, in a stationary mode, flow reactors operate. In contrast, the pulsed and static reactors operate in a non-stationary mode. Steam conversion of carbon monoxide is the CO reaction with steam, which products are hydrogen and carbon dioxide are used for increase in amount of hydrogen

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in synthesis – gas. The reaction is thermodynamically reversible, so the final stage of the reaction is attempted at a minimum temperature to increase the yield of hydrogen. In a number of cases, the reverse reaction of the reduction of CO2 by hydrogen is used to reduce the H2/CO ratio in the synthesis gas. Steam conversion of hydrocarbons is a catalytic process of synthesis gas production from hydrocarbons (methane, propane-butane fraction, etc.) and water vapor. The process is carried out on the modified nickel catalysts at temperatures of 600 – 800°C and characterized by a strong endothermic effect. Steam conversion of hydrocarbons is the main way to produce hydrogen for ammonia production. Stereoregular polymers are polymers with a clearly structured position of the links in space and relative to each other. Straight-run gasoline (naphtha) is a product of primary distillation of oil, fraction of hydrocarbons of a normal structure with number of atoms of carbon usually from 5 to 9 and temperatures of boiling to 180°C. It is gasoline produced by the primary distillation of crude oil. It contains no cracked, polymerized, alkylated, reformed, or visbroken stock. It is important raw materials for the petrochemical industry. Stripping is the removal (by steam-induced vaporization or flash evaporation) of the more volatile components from a cut or fraction. The structure of the catalyst is the chemical structure of the substances constituting the catalyst. For solid phase catalysts, this term implies, in particular, the features of the chemical structure of the surface of a solid. Structurally insensitive reactions are reactions for which the specific catalytic activity does not depend on the size of the catalytically active phase. For example, the majority of reactions of hydrogenation with participation of metal catalysts are structurally insensitive. Structurally sensitive reactions are reactions for which the specific catalytic activity depends on the size of the catalytically active phase. Typical examples are hydrogenolysis and isomerization reactions of hydrocarbons on metal catalysts. Reactions proceed at multicenter adsorption of hydrocarbons on a surface of an active component that demands presence of a certain geometry of an arrangement of atoms of metal on the surface of the catalyst. Reducing the size of the particles of the active component (usually less than 2-3 nm) or the formation of alloys disrupts the arrangement of atoms on the surface, which leads to a sharp decrease in the rate of structurally sensitive reactions. Structural promoter is a substance added in small amounts to the catalyst in order to modify the chemical properties of the active component. The effect of the structural promoter can be associated, for example, with the creation of defects in the crystal lattice or a change in the electronic structure of the catalyst, which affects the strength of chemisorption. Unlike the texture promoter, the structural promoter changes the activation energy of the process or the isotherm of adsorption of any substance involved in the process. The structural promoter is, for example, potassium oxide as part of an iron catalyst for the synthesis of ammonia (affects the chemisorption of hydrogen). Sulfuric acid treating is a refining process in which unfinished petroleum products such as gasoline, kerosene, and lubricating oil stocks are treated with sulfuric acid to improve their color, odor, and other characteristics. Sulfurization is combining sulfur compounds with petroleum lubricants.

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Supramolecular structure is the structure of particles formed from molecular associates (micelles, membranes, vesicles, mesophases, etc.). The structure and spatial organization of such supramolecular structures are provided by intermolecular bonds. Surplus (excess) surface energy is the thermodynamic characteristic of the interface of two equilibrium phases, determined by the work of reversible isothermokinetic formation of this interface, provided that the temperature, volume of the system and the chemical potentials of all components in both phases remain constant. Atoms on a surface owing to coordination nonsaturation have bigger energy in comparison with atoms in volume of this phase. Excess superficial energy can be defined, for example, as superficial excess of free energy of Gibbs. Suspension is a system with the liquid dispersive medium and a solid disperse phase with a size of particles of a disperse phase more than 10 μm. Suspension polymerization is the polymerization of an emulsion of a liquid monomer (its droplets immiscible with the medium, usually water) stabilized with water-soluble organic substances or inorganic salts to form a polymer slurry, i.e., a slurry of a solid in a liquid medium. The polymerization initiator is soluble in the monomer. The growth of the polymer chain itself occurs in the drops of the monomer. Sweetening are processes that either remove obnoxious sulfur compounds (primarily hydrogen sulfide, mercaptans, and thiophens) from petroleum fractions or streams, or convert them, as in the case of mercaptans, to odorless disulfides to improve odor, color, and oxidation stability. Switch loading is the loading of a high static-charge retaining hydrocarbon (i.e., diesel fuel) into a tank truck, tank car, or other vessel that has previously contained a low-flash hydrocarbon (gasoline) and may contain a flammable mixture of vapor and air. Syndiotactic polymer is a polymer in which the orientation of the side fragments of the molecular chain relative to the axis of the chain is strictly alternated: each subsequent fragment is oriented in the opposite direction from the previous one. T Tableting is a method of forming powders by squeezing them under a press to form particles of the desired shape (tablets, rings, etc.). In many cases, the addition of plasticizers to the initial powder is required. Tail gas is the lightest hydrocarbon gas released from a refining process. Thermal cracking is the breaking up of heavy oil molecules into lighter fractions by the use of high temperature without the aid of catalysts. The texture of the catalyst is the geometry of the porous space in the particles of solid-phase catalyst. The texture promoter is an inert substance that is present in the heterogeneous catalyst in the form of fine particles and prevents the sintering microcrystals of active phase. The texture promoter physically separates the catalyst particles, as a result of which their fusion slows down during the operation of the catalyst. As texture promoters, substances with a very high melting point (Al2O3, SiO2, ZrO2, Cr2O3, TiO2) are used. Unlike the structural promoter, the texture promoter does not affect the activation energy of the catalytic reaction. The texture promoter is, for example, alumina in the iron catalyst for ammonia synthesis.

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Time of contact is time during which reactionary mixture contacts to the catalyst. For flowing reactors time of contact is determined by division of free volume of the reactor into the volumetric flow rate of initial reactionary mixture. Thermochemical activation is a thermal treatment of solid substance in nonequilibrium conditions with formation of the metastable structures having the increased energy and considerable reactionary ability. As a result of thermochemical activation some elements of structure in a steady crystal lattice are removed, or are replaced with foreign structures which aren't peculiar to initial substance. Thermal cracking is a non-catalytic cracking of hydrocarbons. It flows in the absence of a catalyst at high temperature through a free-radical mechanism. The predominant process is the cleavage of the C-C bond at the β-position with respect to the carbon atom having an unpaired electron. This causes high yields of ethylene during thermal cracking. Thermal decomposition is the chemical decomposition of substances at elevated temperatures without the participation of gaseous compounds from the surrounding atmosphere. The transition diffusion region is an intermediate range of parameters in which molecular diffusion and Knudsen diffusion have approximately equal effects on the catalytic reaction. The majority of reactions with participation of the catalysts possessing a large specific surface in transitional diffusive area. The position of the boundary of the transition region is affected by a number of parameters, for example, the composition of the reaction mixture, the pressure in the gas phase, the pore size distribution, etc. Triphenylmethane (tritane) is a hydrocarbon, a methane derivative in which three of the four hydrogen atoms are replaced by phenyl radicals. Chemical formula C19H16. The radical of triphenylmethane ((C6H5)3C-) is trityl. Triphenylmethane is a colorless solid, soluble in nonpolar organic liquids and insoluble in water. Trifenylmethane group is also included in the composition of triphenylmethane dyes. To triphenylmethane dyes are bromocresol green, or malachite green. Turbulent flow is the flow of a liquid or gas, in which particles of matter make the diverse casual chaotic movements in different directions. At the same time the average speed of particles coincides in the direction with the flow velocity. The tubular reactor is a flow type reactor in which the catalyst is located inside a metal tube. Heating or cooling of the tubular reactor is carried out from the outside by means of an external coolant (liquid or gas). In the industry, apparatuses consisting of a large number of tubes (multi-tubular reactors) are used. Tubular reactors are commonly used for reactions that occur at high rates and are accompanied by significant heat release. Turnaround is a planned complete shutdown of an entire process or section of a refinery, or of an entire refinery to perform major maintenance, overhaul, and repair operations and to inspect, test, and replace process materials and equipment. Turnover frequency (TOF) is a number of acts of catalytic transformation on one active center of the catalytic agent for a unit of time. The term is used to refer to the turnover per unit time, as in enzymology. For most relevant industrial applications, the turnover frequency is in the range of 10−2 – 102 s−1 (enzymes 103 – 107 s−1). Turnover number of catalase is maximum i.e. 4·107 s−1. TOF represents the most accurate measure of catalytic activity, allows to compare activity of different catalytic agents. In some cases the number of the active centers is unknown, for

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example, in heterogeneous photocatalysis. Then use the surface frequency of turns, i.e. number of acts of catalytic transformation for a unit of time on unit of the surface measured on nitrogen adsorption by the BET method. V Vacuum distillation is a process of separating petroleum hydrocarbon mixtures into components under reduced pressure, based on the difference in their boiling points. The use of a reduced pressure allows reducing the boiling point of the components, since at atmospheric pressure the heavy components decompose earlier than they boil out. It is the distillation of petroleum under vacuum which reduces the boiling temperature sufficiently to prevent cracking or decomposition of the feedstock. Vacuum distillation is used for a finer separation of residual atmospheric distillation (mazut, fuel oil). Its products are gas oils and residues (for example, tar). Vacuum gas oils are used as components of diesel fuel, and also as raw materials for the process of catalytic cracking and a number of others. The valence band is the highest energy of the continuum of energy levels in the solid, which are completely occupied by electrons at 0 K. The valence band is lower in energy than the conduction band and in semiconductors is usually completely filled. When heated, the electrons jump through the forbidden zone from the valence band to the conduction band, which makes the material conductive. The Fermi level at an energy EF separates the valence band from the conduction band. In metals, the valence band is a conduction band. Valine (α-aminoisovaleric acid) (CH3)2CH-CH(NH2)-COOH is one of the most common natural amino acids, is part of almost all proteins, some antibiotics, found in free form in animals and plant organisms. Valine is an essential amino acid. Vapor is the gaseous phase of a substance that is a liquid at normal temperature and pressure. Visbreaking is viscosity breaking i.e. a low-temperature cracking process used to reduce the viscosity or pour point of straight-run residuum. Viscous flow is a physical condition in which a highly elastic polymer passes when heated. Polymers can flow in this state. The volumetric rate is the ratio of the volume of the reaction mixture supplied per hour to the inlet of the reactor to the bulk volume of the catalyst in this reactor. This term is used for both liquid and gaseous reaction mixtures, the conditions for determining the volume of the mixture can be reduced to standard and differ from the conditions of the process. Vulcanization accelerators are chemical compounds introduced into the rubber mixture to accelerate the vulcanization process and improve the physicomechanical properties of vulcanizates. The best accelerators that reduce the dosage of sulfur necessary for vulcanization, affecting the vulcanizate structure, promoting the “crosslinking” of rubber molecules in the desired direction, are organic vulcanization accelerators. The most important of these are aldehydamines (for example, the condensation product of two molecules of aniline with acetaldehyde molecules ensures the production of heat-resistant rubbers); guanidines (ultrasonic accelerators); tiurams (able to vulcanize rubber independently in the absence of sulfur, give rubber with high resistance to aging); xanthogenates (used for self-vulcanizing adhesives); sulfenamides (slowly act in the initial stages of vulcanization, which prevents

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premature vulcanization and gives the rubber increased bond strength of sulfonated rubbers, and also promotes good spreading in molds). Accelerators undergo complex chemical transformations and are consumed during the vulcanization process. W Wet gas is a gas containing a relatively high proportion of hydrocarbons that are recoverable as liquids. Wet impregnation – see diffusion impregnation. Width of the forbidden band is a difference of energy of a conduction band and energy of the forbidden band of substance. In semiconductors and insulators (dielectrics) it is a difference of energies between a bottom (lower level) of a conduction band and a ceiling (upper level) of the valence band. The Wilkinson catalyst is chloride tris(triphenylphosphine) of rhodium [(Ph3P)3Rh]Cl, a homogeneous catalyst for the hydrogenation of a double or triple bond in hydrocarbons. X gel.

Xerogel is a structure obtained by removing a liquid dispersion medium from a Z

Zeolites are natural or synthetic aluminosilicates which crystal structure contains regular system of cavities and channels with sizes of 0.2-1.5 nm. The structure of zeolites represents a three-dimensional framework from tetrahedral fragments [SiO4] and [AlO4] at which there are counterion (cations of metals, H+, NH4+, etc.) compensating a negative charge. Zeolites are used in catalysis as solid acids, in particular, as an active component of catalysts of cracking. Ziegler-Natta process is a catalytic reaction of polymerization of α-olefins with formation of stereoregular polymers. In the industry the catalysts prepared from αTiCl3 and alkyls of metals like Al(C2H5)2Cl are used. Zinin’s reaction is a method of obtaining aromatic amines by reduction of nitro compounds. The reaction was discovered by N.N. Zinin in 1942; as a reducing agent, he used ammonium sulfide or hydrogen sulphide. Acting on nitrobenzene with ammonium sulfide, he produced aniline. Later, Zinin showed that the reaction he discovered was of a general nature. The principles of the Zinin reaction formed the basis for the synthesis of various aromatic amines, many of which serve as starting materials in the production of synthetic dyes, pharmaceuticals, explosives, fragrances, medicines, and other substances. The wide application of Zinin’s reaction has largely determined the development of organic synthesis. Subsequently, to reduce the aromatic nitrocompounds began to use cast-iron shavings in an acidic environment. However, the ammonium sulfide used by Zinin as a reducing agent has retained some importance for the production of amines of the anthraquinone series and mainly for the partial reduction of di- and poly-nitrocompounds.

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Contents    TERMS AND ACRONYMS --------------------------------------------------------- 3 INTRODUCTION ---------------------------------------------------------------------- 6 Part I. THE CATALYTIC REDUCTION OF AROMATIC NITRO COMPOUNDS -------------------------------------------------------------------------- 9 Chapter 1. Aromatic nitrocompounds ------------------------------------------- 9 1.1. Typical representatives of aromatic nitro compounds, properties -- 9 1.2. Application of nitro compounds. Amines production from nitro compounds ---------------------------------------------------------------------- 12 1.3. Aromatic amines: brief information ------------------------------------ 13 Chapter 2. The reduction reaction of aromatic nitro compounds ------------- 15 2.1. The vapor phase hydrogenation of nitro compounds ----------------- 16 2.2. Liquid-phase hydrogenation of nitro compounds --------------------- 18 2.2.1. Reduction by molecular hydrogen ------------------------------------ 19 2.2.2. Processes with participation of compounds – hydrogen donors. Catalytic hydrogen transfer (CHT)------------------------------------------- 19 2.2.3. Electrochemical reduction of nitro compounds --------------------- 22 2.2.4. Reduction by carbon monoxide and its complexes ----------------- 23 2.2.5. Reduction of nitro compounds by different reductants ------------ 24 LITERATURE to Part I ------------------------------------------------------------ 27 Part II. FEATURES OF CATALYTIC REDUCTION OF AROMATIC NITRO COMPOUNDS BY MOLECULAR HYDROGEN ------------------- 33 Chapter 3. Adsorption of nitro compounds and intermediates of their reduction on catalysts --------------------------------------------------------------- 33 Chapter 4. Quantum-chemical description of the reactivity of molecules in liquid-phase hydrogenation processes -------------------------------------------- 45 LITERATURE to Part II ----------------------------------------------------------- 56 Part III. MECHANISM OF CATALYTIC REDUCTION OF AROMATIC NITRO COMPOUNDS --------------------------------------------------------------- 62 Chapter 5. Ideas of D.V. Sokolsky. Four mechanisms of the liquid-phase hydrogenation offered by D.V. Sokolsky ---------------------------------------- 62 Chapter 6. Different variants of the mechanisms of hydrogenation of nitrobenzenes and intermediate products of reduction of the nitro group --- 67 Chapter 7. Study of effect of the nature of the substituent at the catalytic reduction of aromatic nitro compounds ------------------------------------------ 83 Chapter 8. The mechanism of catalytic reduction of aromatic nitro compounds created by Ya.A. Dorfman ------------------------------------------ 99 LITERATURE to Part III ---------------------------------------------------------- 107

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Part IV. CATALYSTS FOR LIQUID-PHASE HYDROGENATION OF AROMATIC NITRO COMPOUNDS ---------------------------------------------- 119 Chapter 9. Catalysts based on copper and nickel ------------------------------- 119 Chapter 10. Catalysts based on precious metals -------------------------------- 123 10.1. Palladium catalysts in the processes of catalytic hydrogenation of nitro compounds ------------------------------------------------------------- 123 10.1.1. Structure of palladium catalysts -------------------------------- 123 10.1.2. Activation of hydrogen on active centers of palladium catalysts and the role of different forms of hydrogen in hydrogenation ----------------------------------------------------------- 127 10.1.3. Hydrogenation of the nitro group in nitrobenzene on Pd supported catalysts----------------------------------------------------- 130 10.2. Hydrogenation of aromatic nitro compounds of various structures on platinum group metals ----------------------------------------- 132 10.3. Hydrogenation of the nitro group and aromatic ring in nitrobenzene, p-, m-, o-nitroanilines on Pd and Rh-containing catalysts -------------------------------------------------------------------------- 137 10.3. Study of the hydrogenation of nitrophenols and nitroanilines under various process conditions on Pd, Pd-Pt, Pd-Cu catalysts --------- 140 10.4. Hydrogenation of nitro compounds on catalysts based on palladium-, platinum-containing carbon nanomaterials --------------- 149 Chapter 11. Catalysts based on rare-earth elements (REE) for the catalytic hydrogenation of nitro compounds ----------------------------------------------- 159 LITERATURE to Part IV ---------------------------------------------------------- 163 PART V. TECHNOLOGICAL ISSUES OF CATALYTIC HYDROGENATION OF AROMATIC NITRO COMPOUNDS ------------ 177 Chapter 12. Variants of instrumental laboratory design for hydrogenation of aromatic nitro compounds ------------------------------------------------------ 179 12.1. Tests on a catalytic installation of atmospheric pressure based on a "catalytic duck" ----------------------------------------------------------- 179 12.2. Apparatus for the study of hydrogenation at elevated pressure --- 181 12.3. Flowing installations ---------------------------------------------------- 192 Chapter 13. Enlarged laboratory tests -------------------------------------------- 197 13.1. Catalytic reduction of o-, p-nitrophenol; p-nitroaniline ------------ 197 13.2. Catalytic reduction of p-NDA. Synthesis of a color-developing agent, CDA-1 ------------------------------------------------------------------- 198 13.3. Catalytic reduction of the Na salt of 4,4'-dinitrostilbene-2,2'disulfonic acid ------------------------------------------------------------------ 202 13.4. Catalytic reduction of 2,4-dinitrotoluene ----------------------------- 203 LITERATURE to Part V ----------------------------------------------------------- 204 PART VI. CATALYTIC HYDROGENATION OF AROMATIC HYDROCARBONS -------------------------------------------------------------------- 209 Chapter 14. General Information-------------------------------------------------- 209

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14.1. Aromatic hydrocarbons. Importance of the process of aromatic hydrocarbons hydrogenation ------------------------------------------------- 209 14.2. Fundamentals of catalytic hydrogenation processes of processing of oil raw materials ------------------------------------------------------------- 212 Chapter 15. General issues of aromatic hydrocarbons hydrogenation ------- 219 15.1. Theoretical bases of aromatic hydrocarbons hydrogenation ------- 219 15.2. Hydrogenation of benzene---------------------------------------------- 232 15.2.1. Hydrogenation of benzene at low pressure ------------------------ 232 15.2.2. Hydrogenation of benzene at high pressure------------------------ 236 Chapter 16. Catalysts of hydrogenation processes------------------------------ 238 16.1. Catalysts of hydrogenation of aromatic hydrocarbons-------------- 243 Chapter 17. Hydrogenation of polynuclear aromatic hydrocarbons ---------- 251 LITERATURE to Part VI ---------------------------------------------------------- 262 PART VII. HYDROGENATION OF HYDROCARBONIC RAW MATERIALS --------------------------------------------------------------------------- 268 Chapter 18. Processes examples -------------------------------------------------- 269 18.1. Installation of hydrotreating of diesel fuel --------------------------- 271 18.2. Hydrotreating of vacuum distillates ----------------------------------- 272 18.3. Hydrotreating of oil residues ------------------------------------------- 273 LITERATURE to Part VII --------------------------------------------------------- 276 CONCLUSION ------------------------------------------------------------------------- 278 GLOSSARY ----------------------------------------------------------------------------- 280

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Scientific issue Aubakirov Yermek Aytkazynovich Sassykova Larissa Ravil’evna

SELECTIVE CATALYTIC REDUCTION OF AROMATIC NITRO COMPOUNDS AND HYDROCARBONS Monograph Computer page makeup: A. Aldasheva Cover designer: A. Kaliyeva IS No. 12007 Signed for publishing 18.05.2018. Format 60x84 1/16. Offset paper. Digital printing. Volume 21.12 printer’s sheet. Edition 50. Order No. 2887. Publishing house «Qazaq university» Al-Farabi Kazakh National University, 71 Al-Farabi, 050040, Almaty Printed in the printing offi ce of the «Qazaq university» publishing house