The Correlation of Sulfur Content and Other Characteristics of Crude oil. The Abiogenic Contribution to Oil and Gas Formation

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Chemistry and Technology of Fuels and Oils, Vol. 43, No. 4, 2007

CURRENT PROBLEMS. The Genesis of Oil and Gas Systems

THE CORRELATION OF SULFUR CONTENT AND OTHER CHARACTERISTICS OF CRUDE OIL. The Abiogenic Contribution to Oil and Gas Formation

M. A. Lur’e and F. K. Shmidt

UDC 546.22:542.945.2:553.98:622.323

The reaction of endogenous methane with sulfur is one of the hypothetical methods of formation of the abiogenic constituent of oil and gas systems. It could be the initial stage of condensation transformations of methane and be responsible for correlations between the concentration of sulfur and many of the physicochemical characteristics of crude oil. The key role of these transformations is confirmed by the effect of the sulfur content of crudes on the scales of oil pools. This dependence is manifested on both the continental and on the local levels. Despite the fact that many questions related to assessing resources and prospecting for oil and gas fields are resolved regardless of the views on the genesis of oil and gas systems, the urgency of a comprehensive examination of this important innate scientific problem is still strong. The insufficiently convincing and weak observational base of co-existing biogenic and abiogenic concepts and the impossibility of conducting adequate full-scale experiments due to the large space and time scales of the systems do not allow elucidating some important aspects of naphthidogenesis. The results of geological observations and geochemical, geophysical, and thermodynamic studies cast doubt on the statement that the biomaterial of sedimentary rocks is the only initial matter for formation of oil and gas systems. A pronounced process of renewal of hydrocarbon reserves takes place in some developed fields [1]. The drawbacks of the sedimentary-migration theory are set out in detail in many publications, in [2-4] in particular. The abiogenic concept is a relatively reliable basis for analyzing information on oil and gas formation. According to this concept, the genesis of fossil fuels is part of global evolutionary processes of differentiation of ____________________________________________________________________________________________________ Institute of Petroleum and Carbon Chemical Synthesis at Irkutsk State University. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 4, pp. 3 – 6, July – August, 2007. 0009-3092/07/4301–0263  2007 Springer Science+Business Media, Inc.

263

Earth’s matter and transfer of matter and energy from the inner spheres of the planet to the periphery and outer space. Abiogenic formation of natural hydrocarbons due to overall processes of development of geospheres was proposed by D. I. Mendeleev, who advanced the idea of the mantle origin of petroleum. This hypothesis was further elaborated in the hypothesis of P. N. Kropotkin [5] on the existence of a hydrocarbon branch of deep fluids. This hypothesis was confirmed by the results of many geological studies. Global geodynamic processes, the confinement of large oil and gas pools and fields to regions of active fluid conditions and faults in the crystalline foundation, and the presence of crude oil in foundation deposits strengthen the position of adherents of the abiogenic concept. Fractures under accumulations of crude oil can be petroleogenetic and deposit-forming channels. Approximately 450 industrial oil and gas fields have been discovered, and their reserves partially or totally lie in the foundation; 39 are unique and large, and the crude in these fields contain trace elements which are not present in sedimentary rocks [6]. It is necessary to specify which chemical reactions are key (triggering) in abiogenic gas and oil formation and how real the conditions of preserving enormous volumes of oil and gas in transporting them to Earth’s surface are. The thermodynamic studies (temperature up to 2330°C, pressure up to 2280 MPa) of C–H and C–H–N–O–S systems indicate their stability in the thermobaric conditions of the upper mantle [7]. The metalloporphyrin complexes in crude oil also have high stability up to 500°C: the activation energy of their decomposition is ~222.07 kJ/mole [8]. The subsequent evolution of the notions on formation of oil and gas systems is based on the assumption of their polygenesis. Deep fluids, which are carriers of energy fluxes and sources of abiogenic carbon, participate in the geodynamics of sedimentary basins. When incorporated in the sedimentary mantle, they can mobilize its biogenic resource and lead to integration with deep hydrocarbon systems. Oil and gas formation can thus be considered as the result of the reaction of two differently directed matter-energy fluxes. The characteristics of the abiogenicity of crude oil are clearly manifested in the example of the gigantic Romashkino field and its satellites. Determination of the amount and isotopic characteristics of trace elements showed: some matter in hydrocarbon accumulations is outside of the field of development of the sedimentary mantle; reduced deep fluid C–O–H–N–S systems related to mantle magmatism undergoing polycondensation–polymerization transformations and reacting with matter of biogenic origin are involved in formation of oil pools [9]. According to [10, 11], the scales of deep degassing of hydrocarbons are not comparable to the sedimentary mantle resources, and the contribution of the biomass entrained by migration fluxes of endogenous hydrocarbon fluids is insignificant. The predominance of vertical fluid breakthrough from the bottom of basins is confirmed by the enormously higher entry of deep methane over organic matter reserves in residual rocks [12]. Without the effect of local deep fluid, even in the case of great depths of sedimentary deposits, for example, in the Ul’yanovsk and Kuibyshev regions, Udmurtiya, and western Tatarstan [9], the appearance of large hydrocarbon accumulations is not obligatory. Due to important thinning of the Earth’s crust under them, sedimentary basins are probably primarily the site of accumulation of oil and gas. Thinning of the Earth’s crust under the effect of mantle magmatism and vertical deep fluid fluxes results in formation of areas of fusion and breakthrough of fluid fluxes. It should be noted that only 1/3 of the many sedimentary basins (approximately 600 in the world) contains crude oil [13]. Based on data on the presence of methane and sulfur in the Earth’s deep zones and the reaction potential of the C–H–S system, we previously hypothesized the possibility of condensation transformations of the

264

hydrocarbon branch of fluids during degassing of geospheres [3, 14]. The condensing effect of sulfur on methane or the products of its condensation can be the initial stage of abiogenic petroleum formation. It was also found that the reactivity of the C–H–S system and the characteristics of its evolution are in agreement with the physicochemical characteristics of real crudes, with their group composition, condensability, sulfur content, and the distribution of sulfur by cuts. In addition, based on the observed correlations between the different physicochemical characteristics of crudes, it was hypothesized that the metal content in crudes, particularly vanadium and nickel, the “mantle markers,” is the result of the direct participation of these metals in the genesis of crude oil. Data are presented that suggest that formation of crude oil is a process related to sulfide mineralization to some degree. It should be noted that sulfur is widely used in macromolecular chemistry for formation of polymer structures. Acting as a dehydrogenating and condensing agent, it can not be incorporated in products but instead play the role of an unusual catalyst [15]. Reactions of sulfur with light alkanes followed by formation of C–H–S compounds of all types (thiols → sulfides → thiophenes), hydrocarbons of different molecular weight, and asphalt-resin structures [16] can probably be assigned to the class of “cascade” reactions [17] with bond-forming transformations (primarily C–C) without addition of any other reagents or catalysts. Additional data on the key role of the reaction of deep hydrocarbons and sulfur that confirm the hypothesis concerning the important abiogenic contribution to oil and gas formation are reported here. From our point of view, the qualitative characteristics and scales of generation of endogenous crude are determined by the composition of the generating fluid, primarily its sulfur content, on which the sulfur content, condensability, and volumes of the crude are dependent. The probability of its evolution toward an increase in the sulfur content and condensability of the crude and an increase in formation of reserves should rise with an increase in the sulfur content in the fluid. For this reason, it is necessary to expect a decrease in the proportion of the gas constituent in the system. The proposed characteristics are actually observed in comparing the sulfur content of crude with its reserves and the proportion of gas reserves in oil and gas complexes. Based on the data in [18], the correlations of these indexes for a number of countries are presented in Fig. 1. Note that a decrease in the proportion of gas is not caused by a sharp decrease in its absolute reserves. In Australia, in comparison to Saudi Arabia and Kuwait, they are ~6 times lower [19], and the ratio of gas and oil reserves (G:O) is ~17 times higher. The total amounts of carbon in the oil and gas are approximately equal for Libya and Nigeria [19], although the oil reserves in the former are 1.5 times higher and the proportion of gas is 2 times lower (see Fig. 1), which could be due to the higher sulfur content in the system. The sulfur content in deep fluids in any region, which initiates condensation transformations, thus probably has the determining effect on the relative rates of oil and gas formation. The direct correlation between the sulfur content and reserves of crude oil is not only observed on the continental (see Fig. 1) but also on the local level, particularly in the West Siberian oil fields [18]. According to the organic theory, the sulfur content of crude is considered the result of a secondary process that takes place due to sulfate reduction. On this basis, in opposition to the process observed in Fig. 1, a decrease in the sulfur content of crude with an increase in its reserves should be predicted, since access of sulfate-containing waters to organic matter can be impeded or stopped altogether with intensification of sedimentation and an increase in the amount of organic matter.

265

39

6

3

12

4

-3

C, bln. ton

3

4

1.5

5 1

2 4

5 0

7

(G:C)10 , m /ton

1. 2

7

0.5 3

6 0.5

CS , %

1. 2 2.6

0

Fig. 1. Effect of the sulfur content CS in crude on oil reserves O (solid curve) and ratio of gas and oil reserves G:O (dashed curve): 1) in Saudi Arabia; 2) in Kuwait; 3) in Libya; 4) in Nigeria; 5) in Indonesia; 6) in Australia; 7) in New Zealand. In linking the sulfur content of crude oils with the activity of sulfate-reducing bacteria, it is necessary to keep in mind a number of factors that restrict the occurrence of this process. Bacteria of this type are strictly anaerobic, and their activity can stop at high temperatures. Moreover, the appearance of sulfur in the hydrosphere in the form of readily soluble sulfates and sulfuric acid due to transformation of rock sulfides is probably caused by later processes of relatively endogenous reactions of sulfur with the metallic and hydrocarbon components of the fluids. The condensation effect of sulfur, manifested in the sizes and ratios of oil and gas reserves, should also affect the physicochemical properties of the gases dissolved in crude oil. Actually, statistical processing of data on all crudes in the territory of the former USSR revealed high correlation coefficients between the sulfur content and gas saturation of crudes [18]. Like the G:O ratio, the gas saturation decreases with an increase in the sulfur content. As an example, the data in [18] on crudes from the Bazhenov formation in the Salym field are shown in Fig. 2. Low G:O values, like the gas saturation, are observed at a sulfur content ³0.2%. The composition of the gases dissolved in crudes is of special interest, where methane predominates over its C 2–C 5 homologs, and C2 > C 3 > C 4 > C 5 [18, 20]. We see from Fig. 2 that the amount of methane is not only greater than the total amount of homologs, but the proportion of methane increases with the sulfur content. These phenomena can be explained with the data on the rates of transformation of hydrocarbons under the effect of sulfur. As indicated in [16], with an increase in the molecular weight of the hydrocarbons, their reaction with sulfur is sharply accelerated, which should result in depletion of the gas constituent by components of higher molecular weight. Seepage of methane from the depths of the Earth is also not excluded. The characteristics shown in Figs. 1 and 2 allow drawing a conclusion concerning the determining effect of the fluid sulfur content on some characteristics of the oil and gas system. The result of comparing the isotopic compositions of mantle, marine-oceanic, and sedimentary sulfur could be one of the most important arguments in support of an opinion concerning the source of sulfur in crudes. Mantle sulfur contains from 0 to 3% 34 S isotope, marine and oceanic sulfate sulfur contains approximately 20%, and contemporaneous marine sediments contain from –55 to 20% [21]. We also know [21] that bacterial reduction of hydrosphere sulfates causes important impoverishment of sulfur in 34S isotope. Negative values of ä 34S are probably also a consequence of this. For most West Siberian 266

crudes, it is 0.4-4.3% (close to the figure for mantle sulfur) and only two of these crudes were poor in this isotope (–3.5 and –7.4) [18]. The isotopic composition of sulfur of different types thus demonstrates the possibility of incorporation of mantle sulfur in crude oil. To some degree, “adulteration” of the sedimentary form as a result of sulfate reduction is probably possible. The variety of natural hydrocarbons is probably due to the inhomogeneity of the composition of deep fluid systems. There are also many variants of the qualitative and quantitative compositions of these systems and subsystems that differ in geochemical specialization and physicochemical properties, and some of the subsystems “specialized from the beginning in transfer of carbon and sulfur” [22]. Reduced high-carbon fluid systems contain characteristics mantle “markers” (nickel, vanadium, cobalt, chromium, etc.) [23] found in crude oil. In the case of nonsulfurous fluid, methane can probably be converted into gas hydrates. Sulfur should not be expected at sites containing them. For example, the results of studying the compositions of formation gases and waters from the largest Messoyakha deposit of gas hydrates [24] showed: the gases contain no sulfurcontaining components; the water in 30% of the wells contains no SO 42- anions, and the content of this anion in the remaining wells is less than 1% of the total anions. Absence of sulfur in the vicinity also indicates the low probability of formation of gas hydrates due to reduction of carbon dioxide during hydrothermal activity, since both carbon dioxide and SO 42- anions should be present in the waters. Although gas hydrates have been detected in many places in the Pacific Ocean, crude oil was not found under them [25], probably due to the absence of sulfur in local fluids. We can legitimately hypothesize that in moving to the surface of the Earth and forming oil accumulation centers (poles), abiogenic crude can to some degree “spread” and mix with biogenic structures by lateral migration. The proportion of abiogenic crude will thus decrease from the accumulation center to the periphery. The physicochemical properties of the system should change correspondingly, forming unique concentric zonality. Zonality of this type actually appears in the basic productive complexes of West Siberia [18]. More than ten properties change unidirectionally. The density, content of asphalt-resin components, and sulfur, the S:N ratio, proportion of methane relative to its homologs, total content of trace elements and porphyrins, proportion of vanadium, and VO- and Ni-porphyrin ratio decrease in the direction from the center. However, gas saturation and the P:Ph (pristine:phytane) ratio increase. In addition, the ratios of m- and o-xylenes, xylenes and ethylbenzene, six- and five-member naphthenes, and the proportion of such

400

300 N

2

Fg, m3/m3

3

200 1 100 0.2

0.4

CS , %

0.6

0.8

Fig. 2. Effect of the sulfur content C S in crude on the proportion N of methane in C2 gases dissolved in West Siberian crude (solid curve) and gas factor GF (dashed curve). 267

metals as nickel, iron, manganese, copper, and chromium increase. It is also possible that the observed changes in the content of asphaltenes, resins, and porphyrins are partially due to their weak ability to migrate due to high adsorbability. The data reported here demonstrate the key role of condensation transformations of deep methane under the effect of sulfur and the determining effect of these processes on many properties of crude oil and the validity of the concept of the polygenesis of petroleum systems. Deep carbon can probably create hydrocarbon systems along two pathways. One is oxidation with formation of atmospheric carbon dioxide and conversion into biomass during photosynthesis, followed by transformation into oil and gas systems. The other path could be direct condensation of the hydrocarbon constituent of fluids in the key role of the effect of endogenous sulfur. In conclusion, we emphasize that the participation of sulfur in global processes of differentiation of Earth’s matter is probably not limited to the proposed oil-forming role of endogenous sulfur. Sulfide mineralization was mentioned above. Moreover, the new hypotheses advanced in the past 15-20 years (thioether and pyrite) of the origin of life [26] also imply the key role of sulfur and are based on the evolution of sulfur compounds. An important role is attributed to organic sulfides and iron and nickel sulfides as polymerization and formation of cell structures from simple molecules – carbon monoxide, methanethiol – can take place on their surface. As indicated in [16], organic sulfides and mercaptans are formed as a result of the reaction of a light alkane with elemental sulfur. REFERENCES 1.

E. G. Areshev, Oil- and Gas-Bearing Basins in the Pacific Ocean Mobile Belt [in Russian], Avanti, Moscow (2004).

2. 3.

A. S. Eigenson, Khim. Tekhnol. Topl. Masel, No. 3, 3-5 (1998). M. A. Lur’e and F. K. Shmidt, Ross. Khim. Zh., 48, No. 6, 135-147 (2004).

4.

V. I. Dyunin and V. I. Korzun, Hydrodynamics of Oil-and Gas-Bearing Basins [in Russian], Nauchnyi Mir, Moscow (2005).

5. 6.

P. N. Kropotkin, Sovet. Geol., No. 47, 104-125 (1955). V. D. Kukuruza, V. D. Krivosheev, V. V. Makogon, et al., in: Fundamental Problems in Oil and Gas

7.

Hydrology [in Russian], GEOS, Moscow (2005), pp. 114-117. V. S. Zubkov, V. A. Bychinskii, and I. K. Karpov, Geol. Nefti Gaza, No. 2, 59-63 (2000).

8. 9.

A. V. Kudel’skii, See [6], p. 107-112. R. P. Gottikh, B. I. Pisotskii, D. K. Nurgaliev, et al., Otechest. Geol., No. 3, 3-11 (2005).

10.

V. M. Zav’yalov, in: International Conference on Degassing of Earth: Geodynamics, Geofluids, Oil, and Gas, Moscow, May 20-24, 2002 [in Russian], GEOS, Moscow (2002), pp. 325-327.

11. 12.

B. M. Valyaev, Toplivno-energ. Kompleks, No. 3, 42-44 (2003). G. I. Voitov, E. I. Mikadze, and I. N. Puzich, Geokhimya, No. 6, 661-672 (2005).

13. 14.

V. A. Trofimov and V. I. Korchagin, Geol. Nefti Gaza, No. 2, 51-54 (2005). M. A. Lur’e, I. Z. Kurets, and F. K. Shmidt, Khim. Tekhnol. Topl. Masel, No. 1-2, 3-5 (2003).

15. 16.

V. I. Nedel’kin, B. A. Zachernyuk, and O. B. Andrianova, Ross. Khim. Zh., 49, No. 6, 3-10 (2005). M. G. Voronkov (ed.), Reactions of Sulfur with Organic Compounds [in Russian], Nauka, Novosibirsk

17.

(1979). V. P. Litvinov, Ross. Khim. Zh., 49, No. 6, 11-20 (2005).

18.

I. V. Goncharov, Geochemistry of West Siberian Crudes [in Russian], Nedra, Moscow (1987).

268

19. 20.

N. A. Savost’yanov, Geol. Nefti Gaza, No. 6, 57-60 (2002). I. I. Nesterov, Ibid., No. 2, 38-47 (2004).

21. 22.

Interpretation of Geochemical Data [in Russian] Itermet Inzhiniring, Moscow (2001). F. A. Letnikov, Geol. Rudn. Mestorozhdenii, 43, No. 4, 291-307 (2001).

23. 24.

F. A. Letnikov, Dokl. Ross. Akad. Nauk, 401, No. 2, 205-207 (2005). S. E. Agalakov, A. R. Kurchikov, and A. N. Baburin, Geol. Geofiz., 42, No. 11-12, 1785-1791 (2001).

25.

N. A. Eremenko and G. V. Chilingar, Geology of Oil and Gas at the Turn of the Century [in Russian], Nauka, Moscow (1996).

26.

V. N. Bashkin and N. S. Kasimov, Biogeology [in Russian], Nauchnyi Mir, Moscow (2004).

269

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 4, 2007

TECHNOLOGY

PRODUCTION OF NARROW-DISTILLATION OIL DISTILLATES

R. G. Gareev

UDC 665.637.046.5

Modern technology for production of the entire spectrum of narrow-distillation oil distillates for manufacture of base oils using the latest contact devices and a new system for creating the vacuum in the vacuum tower is examined. Narrow-distillation distillates are necessary for manufacturing high-quality lube oils from petroleum feedstock [1, 2]. High-efficiency contact devices with low resistance to movement of the vapor stream and low residual pressure, a maximum of 6.5 kPa, in the atmospheric resid fractionation system ensure such distillates. Table 1 Feedstock and products

wt. %

tons/hour

tons/day

thous.tons/year

Taken 100.0

125.000

3000

1038.000

Decomposition gases and petroleum product

Obtained 1.1

1.375

33

11.418

Solar cut

6.0

7.500

180

62.280

low-viscosity

11.0

13.750

330

114.180

viscous

17.0

21.250

510

176.460

medium viscosity high viscosity

12.0 17.5

15.000 21.875

360 525

124.560 181.650

Black cut

5.4

6.750

162

56.052

Vacuum resid

30.0

37.500

900

311.400

100.0

125.000

3000

1038.000

Atmospheric resid

Oil distillate

Total Note.

The duration of operation of the vacuum block is equal to 346 days a year.

____________________________________________________________________________________________________ Vostokneftezavodmontazh Planning Institute. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 4, pp. 7 – 9, July – August, 2007. 270

0009-3092/07/4301–0270 © 2007 Springer Science+Business Media, Inc.

Narrow-distillation distillates can be obtained in an amount close to their potential content in atmospheric resid by “dry” distillation of atmospheric resid [3] or fractionation using steam as the stripping agent. Vacuum distillation of atmospheric resid without use of steam is possible if there is no severe requirement for the flash point of the vacuum resid. It is used when residual distillate corresponding to deasphalted product in quality [3] and heavy vacuum resid with a density greater than 1000 kg/m 3 and a minimum flash point of 300°C must be separated at low residual pressure.

VII

11 XV

VIII

8 1 7 26

10

8

VI 1 2 1

V

2

7 6 2

III

1

7 6

12

9

7 6

1

2

7

6

IV

13

9

14 9

9 8

7

II 2

I X

6 4 5

3 4 5

3

XI 15

16

I IX

1

XIV 2

XII 1 XIII 2

Fig. 1. Diagram of the vacuum block for distillation of atmospheric resid with steam: 1) heat exchanger; 2) pump; 3) furnace; 4) input device; 5) stripping section tray; 6) liquid collector; 7) packing layer; 8) nozzle liquid distributor; 9) hydrodynamic liquid distributor; 10) vacuum tower; 11, 12) horizontal and vertical vacuum capacitors; 13, 14) stages I and II hydraulic injectors; 15) fire wall; 16) three-phase separator; I) atmospheric resid; II) black product; III, IV, V, VI) high-viscosity, medium-viscosity, viscous, and low-viscosity oil distillates; VII) solar cut; VIII) decomposition gases and light hydrocarbons to vacuum-creating system; IX) steam; X) vacuum resid; XI) uncondensed decomposition gases to furnace for complete burning; XII) water condensate; XIII) circulating working liquid (diesel fuel cut); XIV, XV) direct and reverse cooling water. 271

Table 2 Product of vacuum fractionation of atmospheric resid with steam

viscous

high-viscosity

Density at 20°C, kg/m3 Distillation temperature, °C 5% 95 %

medium-viscosity

Indexes

low-viscosity

oil distillate

951

870

888

910

923

936

1070

335 –

287 332

335 382

381 431

430 468

468 568

542 –

– 32

2 –

8.2 –

23.3 –

– 0.5

– 26.6

– –

– 134

– 77

– 177

– 208

– 234

– 258

178 332

–

–

0.5

2

3

5.5

–

Atmospheric resid

solar fraction

vacuum resid

Viscosity kinematic, mm2/sec at 50°C at 100°C nominal (Engler)* at 100°C Flash point (open cup), °C Color, CST units Note.

* Determined on an asphalt viscometer 5 mm in diameter

Atmospheric resid is distilled using steam as the stripping agent in one of the oil refineries. Preliminary calculation analysis of the process in a mathematical model of the entire subsystem of distillation of atmospheric resid using packing contact devices of the Gempak type demonstrated the possibility of obtaining the entire spectrum of narrow-distillation distillates. The configuration of the vacuum tower internals in this case differs from the configuration described in [3] due to the presence of a stripping section consisting of five valve trays. The vacuum block is designed for processing one million tons/year of atmospheric resid from a commercial mixture of West Siberian crudes in one tower without external stripping sections. Atmospheric resid from the atmospheric part is heated in an updated inverted V A-type furnace. To improve the conditions of its evaporation in the double-flow furnace coil and consequently to increase input of heat into the vacuum tower at the same temperature, the tube coils are made with a variable section: from 127×10 mm at the inlet to 326×9 mm at the outlet. The transfer pipelines are also made of four sections of variable cross section: from 377×9 mm at the beginning to 630×8 mm at the end. As a result, it was possible to ensure low residual pressure at the beginning of the furnace coils and to obtain evaporation of ~65 wt. % of the atmospheric resid at the furnace outlet. The amount of heat put into the vacuum tower and the energy loss of the steam-liquid mixture attained the maximum possible value at the entry into the tower. At a temperature of 387°C and residual pressure of 5 kPa in the tower feed zone, the distillation fraction attained ~80 wt. %. Such a distillation fraction is sufficient if we consider the characteristics of fractionation of hydrocarbon mixtures [4]: it should be 2-3 wt. % higher than total distillate takeoff. This is why it is not necessary to use steam for taking off distillates. However, to attain the required (≥260°C) flash point of vacuum resid, it is necessary to feed in steam for stripping.

272

Table 3

Indexes

Fraction of atmospheric resid traditional in the with steam in a vacuum tower of vacuum tower with an A-12/1M unit Gempak packing

Temperature, °C atmospheric resid coming out of furnace

410

400

400

393

vapors in evaporation zone

384

387

at top of tower

100

90

solar fraction at outlet circulating reflux stream I entering upper part of tower

200 60

162 50

243

232

–

120

295 340

281 313

–

352

circulating reflux stream III going into tower

–

352

black product coming out of tower

–

370

vacuum resid coming out of tower

365

377*

–

81

18.67

8.6

at top of tower

8.5

5.6

at bottom of tower

23

11.2

entering stage I ejector

–

4.8

entering tower

circulating reflux stream II (low-viscosity distillate) coming out of tower going into tower distillate coming out of tower medium-viscosity viscous high-viscosity (circulating reflux stream III)

Residual pressure, kPa coming out of furnace in evaporation zone

Note.

*Without quench

Vacuum solar oil, low-, medium-, high-viscosity, and viscous distillates, black product, and vacuum resid are taken off in the vacuum tower. For stripping, 0.8 wt. % steam in atmospheric resid is fed into the bottom of the distillation part of the vacuum tower. A diagram of the subsystem for vacuum distillation of atmospheric resid is shown in Fig. 1. It follows from the material balance of the process (Table 1) that the yield of vacuum resid decreased to 30 wt. %, i.e., 15 wt. % in crude. All distillates are separated within the limits of their potential content in the atmospheric resid. The quality (Table 2) of the low-viscosity, medium-viscosity, and viscous distillates satisfies the requirements for the quality of base oils, and the quality of the high-viscosity distillate satisfies the requirements for the quality of deasphalted product from 36/1.2 units. The 5 to 95% cutpoints of these distillates are respectively 45, 47, 50, 38, and 100°C. The process conditions (Table 3) for operation of the vacuum block according to the proposed scheme (see Fig. 1) in comparison to the process conditions of the vacuum part of analogous type A-12/1M units became 273

markedly milder. This was due to introduction of a liquid-ejector vacuum-creating system (LEVCS) during implementation of the project [5] instead of the steam-injector unit. The LEVCS allows easily providing for the required residual pressure level in the fractionation subsystem. The results of more than three years of operation of this system demonstrate the possibility of maintaining the residual pressure in the separation system within the limits of 1.5-6.5 kPa. The atmospheric resid vacuum distillation block producing narrow-distillation oil distillates operates stably and ensures a minimum yield of vacuum resid of 15-18 wt. % in crude. REFERENCES 1. E. V. Voznesenskaya, A. A. Karaseva, I. V. Novakovskaya, et al., Khim. Tekhnol. Topl. Masel, No. 7, 10-12 2.

(1976). A. K. Manovyan, B. A. Suchkov, O. K. Odintsov, et al., Ibid., No. 7, 34-37 (1975).

3. 4.

N. R. Saifullin and R. G. Gareev, Ibid., No. 6, 8-10 (1999). B. K. Marushkin, Doctoral Dissertation, Ufa Petroleum Institute, Ufa (1976).

5.

RF Patent No. 2094070.

274

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 4, 2007

TECHNOLOGY FOR PRODUCTION OF SOLID WAXES AND LUBE OILS

S. P. Yakovlev and V. A. Boldinov

UDC 665.772

Incorporating a pulsed crystallizer in a combined dewaxing and deoiling scheme demonstrated the prospects for expanding the potentials of this process. Such a combination allows bringing lube oil and wax production to a new level both in technology and in instrumentation. Combined dewaxing and deoiling using a pulsed crystallizer in the stage of production of a wax suspension from raffinate was introduced in production of lube oils and KM-2 waxes at SLAVNEFT’-Yaroslavnefteorgsintez Co. One of the important advantages of this process, together with improved process indexes (increased takeoff of lube oil, low oil content in wax, etc.), is the replacement of all regenerative scraper crystallizers with a pulsed crystallizer [1-3]. The suspension obtained in the pulsed crystallizers is cooled to the filtration temperature in the first dewaxing stage in the evaporative (propane) scraper crystallizers remaining in the circuit. As a consequence, this technology does not permit totally eliminating scraper crystallizers, which are not very efficient in the heat transfer region, are distinguished by low reliability in operation, and involve high costs for servicing and maintenance. In addition, the crystals of low-molecular-weight “soft” waxes separated from the feedstock solution at lower temperatures, combined with the “hard” waxes crystallized at higher temperatures, form a polydisperse solid phase. This negatively affects the filtration characteristics of the suspension obtained. The increase in the temperature in the next slack wax filtration–deoiling stages causes nonproductive losses of the chill of the suspension obtained in the dewaxing stage. Technology that increases the rate of filtration of the suspension obtained, increases the yield of lube oil with the required solid point while raising its quality, and decreases the oil content in the wax without using ____________________________________________________________________________________________________ Vokstek Ltd.. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 4, pp. 10 – 13, July – August, 2007. 0009-3092/07/4301–0275  2007 Springer Science+Business Media, Inc.

275

scraper crystallizers – regenerative and evaporative – was developed as a result of theoretical and experimental studies. The wax suspension from the pulsed crystallizer is filtered in two or more stages without subsequent cooling to produce wax (see Fig. 1). The mixture of filtrates from two or more stages undergoes catalytic dewaxing after regeneration of the solvent in it, yielding dewaxed oil with a given solid point. In processing feedstock with a low solid wax content, wax obtained in the last filtration stage after removal of the solvent, in an amount that ensures a 17-20 wt. % solid wax content in the feedstock mixture is added before feeding into the pulsed crystallizer. Increasing the concentration of solid waxes in the feedstock mixture if necessary ensures high efficiency of separation of the suspension formed in the pulsed crystallizer at a relatively high filtration temperature corresponding to the slack wax deoiling temperature: the oil content in the wax decreases, and the yield of the filtrate mixture increases. Catalytic dewaxing of the deoiled filtrate mixture increases the yield and viscosity index of the oil with a given solid point.

V

1

IV

VI 3

3

3

2

III

VIII 4

I

VII

IX

5

II XII

X

XI

XIII

XIV

Fig. 1. Diagram of combined production of waxes and lube oils – combination of solvent deoiling and catalytic dewaxing in a pulsed crystallizer: 1) pulser; 2) pulsed crystallizer; 3) filter; 4) block for utilization of cold from filtration products and cooling of solvent in propane (ammonia) coolers; 5) solvent regeneration section; 6) block for hydrotreating and catalytic dewaxing of mixed filtrates; I) feedstock; II) wax to circulation; III, IV) cooled wet and dry solvent; V) suspension; VI) cooled wet solvent to dilution and washing of sediments; VII) mixed deoiled filtrate solutions; VIII) wax sediment; IX, X) wet and dry solvents; XI) mixed filtrates; XII) wax (finished product); XIII) dewaxed oil; XIV) by-products of reactions. 276

T h e e s s e n c e o f t h e p r o c e s s i s d e s c r i b e d i n m o r e d e t a i l b e l o w. F e e d s t o c k h e a t e d t o a temperature 8-12° higher than the initial crystallization temperature of the wax in it is fed into the first section of the pulsed crystallizer (see Fig. 1). A chilled selective solvent is added to the pulsed crystallizer in two streams as coolant. The feedstock mixture in the crystallizer is mixed by the pulsations with the coolant continuously entering the section. The feedstock stream is cooled as it is diluted with the coolants in moving from section to section. The suspension formed in the pulsed crystallizer enters the filters where it is separated in two or three stages. The sediments on the filters are washed with solvent, some of which is used for diluting the sediment between filtration stages. The sediment from the last filtration stage and the mixture of filtrate solutions enter the block for utilization of the chill from the products of separation of the separating and cooling the solvent in propane (ammonia) coolers. The mixture of filtrate solutions and sediment from the last filtration stage then enter the solvent Table 1 Indexes Initial feedstock temperature, °C Amount of wax fed for mixing with feedstock, wt. % in feedstock

Production conditions for solid waxes and lube oils with technology existing proposed 50

50

–

5

1.5:1

–

in lower collector

–

1.5:1

in upper collector

1.5:1

1.5:1

-2

–

in lower collector

–

-2

in upper collector

Amount of coolant fed in pulsed crystallizer, mass fraction in feedstock second-stage filtrate in lower collector chilled solvent

Temperature of coolant fed into pulsed crystallizer, °C second-stage filtrate in lower collector chilled solvent

-20

-20

Temperature of suspension coming out of pulsed crystallizer, °C

+2

+4

Filtration temperature, °C in first stage in second stage

-25

+5

-15

+5

in third stage

+5

+5

1:1

0.7:1

Amount of solvent, mass fraction in feedstock for washing sediment in filters first stage second stage third stage

1:1

0.7:1

0.8:1

0.5:1

1:1

0.7:1

1:1

0.7:1

6.3

6.3

for dilution of sediment after filters first stage second stage Total amount of solvent fed for dilution of feedstock, washing and dilution of sediments, mass fraction in feedstock

277

regeneration section. The distilled solvent is cooled by the filtration products and after additional cooling in propane (ammonia) coolers, is fed into the pulsed crystallizer as a coolant and for diluting and washing the sediments in the filters. Wax is taken from the regeneration section and some is used for feedstock dilution, forming a circulating stream in the system. A balanced amount of wax is taken off as finished product. If necessary, this wax undergoes contact treatment or hydrotreating. The mixed filtrates after the solvent regeneration section are fed into the catalytic dewaxing block, where two processes can take place: hydrotreating and catalytic dewaxing of the mixed filtrates. The advantages of the proposed technology were confirmed by the results of experimental studies. Raffinate of the 420-490°C cut obtained from mixed West Siberian crudes was used as the feedstock and a mixture of 60 vol. % methyl ethyl ketone (MEK) and 40 vol. % toluene was used as the solvent. The basic physicochemical characteristics of the raffinate were; density at 20°C, 893 kg/m 3 ; melting point, 42°C; refractive index, 1.5029 at 20°C; viscosity, 10.3 mm 2/sec at 100°C. The process was modeled with the scheme in Fig. 1. Feedstock mixed with 5% wax previously obtained from it was fed into a model of a pulsed crystallizer where it was mixed with cooled solvent. The suspension obtained was filtered in three stages at the same temperature, washing the sediments in each stage and feeding solvent for diluting the sediments between filtration stages. The basic parameters of the conditions of obtaining the suspension and filtering and washing the sediments are reported in Table 1. The solvent was distilled from the third-stage filtration sediment and mixed filtrate solutions. The mixed filtrates were then catalytically dewaxed using a zeolite-containing aluminum–nickel–molybdenum selective cracking catalyst in the following conditions; feedstock space velocity of 0.5 h -1 , temperature of 370°C, hydrogen-containing gas feed ratio of 1000 nm 3/m 3 feedstock, pressure of 4.5 MPa. The material balance was then formulated and the properties of the products obtained were determined (Table 2). The generalized technical and economic indexes of the existing and proposed processes are reported in Table 3. Table 2 Indexes Solid point, °C Viscosity index Oil content, wt. % Melting point, °C Yield, wt.% in feedstock Solid point, °C Viscosity index Oil content, wt. % Melting point, °C Yield, wt. % in feedstock

Dewaxed oil With existing technology max -15 89 – – 76 With proposed technology max -15 98 – – 80*

Notes. * After catalytic dewaxing of mixed (88 wt. %) deoiled filtrates. ** Reaction products.

278

Wax

Deoiled filtrate

– – max 2

12 – 78

62 12

– 12

– –

– –

under 0.8 63 12

– – 8**

279

Note.

Yes Yes *

No No

*Due to switching off evaporative crystallizer shaft drives and eliminating suspension feed pump to evaporative crystallizers.

Absent

Present

125—130 Less than 40 Excluded

100

Output of unit with respect to feedstock without increasing the total number of filters, %

Yes

70

164

—

100 In full volume

No

Load on cooling section, % Operating costs for repairing an servicing of evaporative scraper crystallizers Container for suspension from the pulsed crystallizer and pump for feeding suspension to evaporative scraper crystallizers Possibility of using low-pressure pumping equipment for feeding feedstock and solvent into pulsed crystallizer and block for cooling solvents with products of separation of the suspension Possibility of reducing power required for electrical equipment

100

Possibility of including* an additional filtration stage without increasing the number of filters

—

Required filtration surface area in terms of the same load in feedstock (raffinate), %

for mixed feedstock (raffinate) and circulating wax

100

Suspension filtration rate, kg/(m2⋅h) for feedstock (raffinate)

3

1

Not used

—

proposed

2

existing

Production of solid waxes and oils by technology

Used

Indexes

Use of evaporative scraper crystallizers

deoiling

dewaxing

Number of filtration stages in

Table 3

The new technology increases the yield of dewaxed oil with a given solid point by 4 wt. % (in terms of raffinate). The oil content in the wax decreased from 2 to 0.8%, which makes it possible to obtain grade P-2 food-quality wax after hydrotreating or contact treatment instead of grade T-2 industrial wax according to GOST 23683–89. The yield of wax in terms of raffinate did not decrease, despite the losses in the form of light petroleum products – by-products of the reactions that take place in the catalytic dewaxing stage. This is due to the fact that the amount of by-product – deoiled filtrate – in the process used as the base was 1.5 times higher. Both oil and wax components of the feedstock are lost with this product. The products of the catalytic dewaxing reaction are delivered to the refinery’s fuel system, where the deoiled filtrate usually enters. In the proposed process, the suspension filtration rate is more than 1.5 times higher, which increases the output of the unit by 25-30% or increases the number of filtration stages. One reason for the improved suspension filtration characteristics is the higher filtration temperature, which reduces the viscosity of the liquid phase of the suspension. The solid wax added to the feedstock is a crystal structure modifier: the concentration of high-molecular-weight waxes that form large homogeneous particles of solid phase on crystallization increases. In refining raffinates with a low solid hydrocarbon content, this additive increases the concentration of solid waxes in the feedstock solution. For this reason, the suspension coming out of the pulsed crystallizer at a relatively high temperature contains enough solid phase to form the thick sediment on the filtering surface required for efficiently conducting the filtration, washing, drying, and blowing stages. Incorporation of solid waxes in this amount in the feedstock stream is only possible for a volume crystallizer such as the pulsed crystallizer. An attempt to use this method for scraper crystallizers resulted in rapid clogging of the pipe space by wax deposits and perturbation of normal operation of the equipment and the process as a whole. The increase in the oil viscosity index is due to the fact that the mixed filtrates from which most of the solid high-molecular-weight n-alkanes were removed undergo catalytic dewaxing. For this reason, the mixed filtrates, enriched with isoalkanes and an insignificant amount of low-molecular-weight “soft” waxes, do not require severe conditions for conducting the reaction. In addition, high-index components, some of which are lost with the deoiled filtrate in refining with the existing technology, remain in the mixed filtrates separated from the solid phase in filtration. Totally eliminating use of scraper crystallizers (regenerative and evaporative) will simplify equipping the unit and will reduce operating costs for maintenance and servicing. Since it is not necessary to chill the suspension to low temperatures, the load on the cooling section is reduced by more than two times. As a result of eliminating scraper crystallizers, it becomes possible to use low-pressure pumps and consequently reduce power consumption. REFERENCES 1.

S. P. Yakovlev, E. D. Radchenko, N. N. Khvostenko, et al., Nauka Tekhnol. Uglevodorov, No. 2, 41-45 (1999).

2. 3.

S. P. Yakovlev, E. D. Radchenko, V. F. Blokhinov, et al., Khim. Tekhnol. Topl. Masel, No. 4, 12-15 (2000). S. P. Yakovlev, E. D. Radchenko, V. F. Blokhinov, et al., Ibid., No. 2, 16-17 (2002).

280

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 4, 2007

PRODUCTION OF GREASES FROM INDUSTRIAL PETROLEUM WASTES

V. V. Ostrikov and E. V. Smolyakova

UDC 621.892.262

Petroleum-containing industrial wastes and petroleum products lost during processes (losses) are quantitatively and qualitatively basic environmental pollutants – of water, soil, and air. Some petroleum wastes from production and use of lubricants (greases, motor and industrial oils, etc.) are collected and regenerated. Wastes which are not regenerated due to their physicochemical properties are dangerous environmental pollutants. The purpose of the present study is to utilize wastes from treatment of used motor oils, sediment containing carbamide, carbenes, carboids, asphaltenes, resins, and additive residues. The possibility of using this sediment as a thickener in production of polyurea greases with used motor oil treated to remove abrasive contaminants as dispersion medium was investigated. Used motor oil basically has a viscosity of 6-10 mm 2 /sec at 100°C, and the dispersion medium of polyurea greases should have a viscosity of 17-64 mm 2/sec at 100°C. Bottoms of C 17 -C20 and C21 -C 25 synthetic fatty acids (SFA) and calcium acetate were used to improve the thickening power of this thickener. The resins found in large amounts in used oil and in sediment improve the lubricity of the grease. Asphaltenes, carbenes, and carboids are in this case like fillers for the grease and serve as modifiers of its structure. The polyurea grease production technology consists of stages of mixing the components of the thickener in oil medium, heating the substitution urea while stirring, homogenization and cooling of the samples obtained.* *V. I. Kucheryavyi and V. V. Lebedev, Synthesis and Use of Carbamide [in Russian], Khimiya, Leningrad (1970). ____________________________________________________________________________________________________ All-Russian Scientific-Research and Design-Process Institute on Use of Technology and Petroleum Products in Agriculture (VIITiN). Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 4, pp. 14 – 15, July – August, 2007. 0009-3092/07/4301–0281  2007 Springer Science+Business Media, Inc.

281

Analogs of polyurea grease were manufactured according to the selected technology. The preparation process was conducted with continuous stirring, which increased the degree of dispersion of the components of the grease and improved its spatial structure and consequently its colloidal stability. The sediment – waste from treating used oils – was heated in treated oil medium to 150-170°C for 0.5-1 h. On heating to 150°C and higher, carbamide was successively transformed into NH 4NCO, NH 4CO 2, biuret, and cyanuric acid, which exists as two tautomers. SFA bottoms and calcium acetate were added to the heated mass. The bottoms and calcium acetate, together with resins and other surfactants (SF), have the properties of modifiers of the structure of the grease. The stabilizing effect of SF is probably due to their adsorption on the surface of particles of thickener with formation of boundary layers or oriented molecules of determined structure that prevent particle aggregation and reduce the number of contacts per unit of volume. After adding the calcium acetate and bottoms, it is useful to continue heating at 160-170°C for 20-25 min. Homogenization of the grease – intensive mechanical treatment in rigorously defined conditions – was conducted to increase its mechanical stability in use. The structure of the greases undergoing homogenization undergoes irreversible changes in the conditions of use only when the intensity of the mechanical effect is greater than in homogenization. Homogenization ensures more uniform distribution of the thickener in the oil and consequently an increase in its thickening effect, creation of homogeneous texture, and improvement of the external appearance of the grease. In addition, perturbation of condensation and formation of a thixotropic coagulation structure take place in homogenization, the degree of dispersion of the thickener increases, and the mechanical and colloidal stability and other characteristics of the grease improve. A dual effect is created in this way: the remaining bonds in the condensation structure are broken and more uniform and fine dispersion of the thickener in the dispersion medium is attained, i.e., the thickening effect is enhanced. In production of greases from polyurea, prolonged (2-3 h) heat treatment at 180-200°C is required after careful homogenization. In our case, in using polyurea-acetate complex, heat treatment at 290-200°C for 1.5-2 h is also necessary. For the greatest utilization of sediment during production of grease, the amount of thickener was brought to 50-70%. For this reason, a higher heat-treatment temperature was provided for: 220-240°C for 1.5-2 h. The technology we recommend for production of polyurea greases from oil regeneration wastes consists of the following stages:

• treatment of used motor oils in a centrifuge to remove abrasive contaminants; • subsequent treatment of the coagulant to remove chemical contaminants – asphalts, carbenes, carboids; • heating the residue from chemical treatment in a medium of abrasive-free oil to 150-170°C for 0.5-1 h; • incorporating bottoms from production of C 17 -C 20 C 21 -C 25 SFA and calcium acetate in the mass obtained while stirring to better distribute the components and heating for 1 h at 160-170°C; • homogenization of the hot mass with a rotary-gear or screw pump: the homogenization effect is attained as a result of repeated pumping with the pump; • heat treatment at 220-240°C for 1.5-2 h;

• gradual cooling. All stages of the process take place with continuous stirring. The studies of four samples of greases obtained showed that all passed tests for protective power for 72 h and tests for the corrosive effect on metals. After washing the greases off, no dark spots, black dots, filaments, or pits were detected on the plates. The surfaces of the plates were clean and shiny.

282

The proposed greases are thus a product obtained as a result of the most complete utilization of wastes from treatment of used motor oils and consequently a prudent attitude toward resources and the environment.

283

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 4, 2007

EQUIPMENT. Theoretical Design Principles

MATHEMATICAL MODEL OF THE DYNAMICS OF NONEQUILIBRIUM ADSORPTION IN A STATIONARY BED

F. V. Yusubov

UDC 66.011.001

The nonequilibrium dynamics of adsorption in a stationary bed of aluminosilicate adsorbent was mathematically described on the example of dearomatization of the 200-320°C fraction of liquid paraffins. The characteristics obtained indicate the important effect of the initial concentration of adsorbate in the feedstock and the temperature and flow rate of the feedstock on the process diffusion parameters. This effect must be taken into consideration in designing industrial adsorbers. In practical calculations, optimization, and design of adsorption processes, determining the effect of temperature, concentration, and hydrodynamic factors on the adsorber output plays an important role [1]. In modern chemical engineering, adsorption equipment is widely used for reacting substances in different aggregate states. Attempting to enhance industrial adsorption processes increases the velocity of the phases

Adsorber (see Fig. 1)

Table 1

А-1 А-2

Stage of process conduced in the period from 1 to 7 hours

from 8 to 14 hours

from 15 to 21 hours

from 22 to 28 hours

Adsorption Decantation and desorption Blowing and dehydration Decantation and desorption Blowing and dehydration Decantation and desorption

А-3

Blowing and dehydration

Cooling

А-4

Cooling

Adsorption

Adsorption

Cooling Adsorption Decantation and desorption

Decantation and desorption Blowing and dehydration

____________________________________________________________________________________________________ Azerbaidzhan State Petroleum Academy. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 4, pp. 16 – 18, July – August, 2007. 284

0009-3092/07/4301–0263 © 2007 Springer Science+Business Media, Inc.

and the local and average adsorbate temperature and concentration gradients in the active zones of sorption equipment [1-3]. New approaches are necessary for mathematically describing sorption processes with inhomogeneous hydrodynamic, concentration, and temperature profiles [4]. According to the scheme of the unit for adsorption dearomatization of liquid paraffins (see Fig. 1), four adsorbers provide for the continuity of the process with respect to feedstock and finished product streams. The process includes several stages: • adsorption of aromatic hydrocarbons from feedstock in the liquid phase by the adsorbent and production of pure paraffins; • removal of feedstock residues from the adsorber and desorption of aromatic hydrocarbons from the pores of the adsorbent with isopropanol; • blowing through the adsorbent with a mixture of superheated steam and blowing gas to remove alcohol;

• dehydration of the adsorbent bed; • cooling of the adsorbent bed to the adsorption temperature with circulating blowing gas. A diagram of operation of the adsorbers is shown in Table 1. The mathematical model of adsorption dearomatization of liquid paraffins in a stationary bed proposed in [5] describes a process conducted in equilibrium conditions. It is a system of differential equations in secondorder partial derivatives. The system is solved with the Laplace–Carson transform. As a result of a series of mathematical operations, the following system of equations is obtained [6, 7]: a* = 2 K a Da (1 / r* )τ a

(1)

a = 2πr02 Da N 1 K a τ a

(2)

C c = 2 K c Dc (1 /r )τ a − a

(3)

K a = a/r0

(4)

II

IV

V

VI

А-1

А-2

А-3

А-4

I

III

III

III

Fig. 1. Process diagram of the unit for adsorption dearomatization of liquid paraffins: A-1-A-4 – adsorbers; I, II – untreated and treated paraffin; III – periodic switching of adsorbers; IV – isopropyl alcohol; V – hot steam; VI – cold inert gas. 285

C c = a/ [b(a ∞ − a )]

(6)

16 16 ⎡ ⎤ C = 0.9 ⎢− C s (S1 ) + C s (S 2 ) − C s ( S 3 )⎥ 3 5 ⎣ ⎦

(7)

(8)

C s = f(De ) S1 = 1 / (2.89τ a ), S 2 = 3 / (2.89 τ a ),

S 3 = 5 / (2.89 τ a )

(9)

where a* is the concentration of adsorbate in micropore formations; Ka , K c are coefficients; D a , D c are the diffusion coefficients of the adsorbate in micropore formations and transport pores; r * is the current radius of the micropore formations; t a is the adsorption time; a is the concentration of adsorbate; r 0 is the radius of the micropore formations; N 1 is the number of micropore formations per unit of volume; Cc is the concentration of adsorbate in transport pores; r is the current radius of the adsorbent grain; b is the Langmuir equation constant; a ¥ is the limiting concentration of adsorbate; C s is the representation of Layla’s transform of function C sought; S 1, S 2 , S 3 are arguments of function C s; D e is the effective diffusion coefficient. Coefficient D e is determined by the random search method based on the criterion

F = C ca − C e ≤ ε where Cca , Ce are the calculated and experimental values of the concentration of adsorbate; ε is some defined accuracy (ε = 0.01). The program for studying and calculating the process parameters of liquid-phase adsorption is written in Fortran-77 and is run on an IBM PC [4]. The nature of the substances in the feedstock, temperature, and feedstock flow rate affect the results of adsorption treatment to a great degree [1]. Feedstock from different fields is frequently used in industrial conditions. For this reason, the concentration of adsorbed substances in it varies, which changes the velocity of the phases and temperature gradients in the active zones of industrial adsorbers (in a stationary adsorbent bed). It then became necessary to study the combined effect of the process concentration, temperature, and flow rate profiles on the diffusion parameters. It became possible to solve this problem with the mathematical model of equilibrium adsorption in a stationary bed of adsorbent reported above. The material balance of adsorption treatment of paraffins is: Taken, thousands of tons/year (wt. %) Fresh feedstock

80.0 (100.0)

Obtained, thousands of tons/year (wt. %) Treated paraffins

75.6 (94.5)

Desorbate Losses

286

3.9 (4.9) 0.5 (0.6)

287

9 36 45 54 63 72 81 90 99 108 117

τ·10−2, sec

Table 3

9 36 45 54 63 72 81 90 99 108 117

τ·10-2, sec

Table 2

Da·1019 0.463 0.231 0.152 0.121 0.093 0.081 0.065 0.054 0.050 0.042 0.027

0.490 0.425 0.400 0.375 0.300 0.200 0.125 0.100 0.075 0.062 0.050

Da·10 19

Dc·109 0.560 0.410 0.270 0.130 0.210 0.060 0.055 0.040 0.025 0.023 0.022

20

0.625 0.600 0.470 0.350 0.275 0.190 0.110 0.750 0.059 0.030 0.020

0.42 Dc·109 0.450 0.425 0.375 0.300 0.225 0.150 0.100 0.090 0.075 0.060 0.050

Da·10 19

0.425 0.400 0.370 0.350 0.275 0.160 1.080 0.050 0.035 0.025 0.020

0.53 Dc·109 39.00 30.00 20.00 13.50 6.00 5.00 4.48 4.00 4.20 6.00 9.00

De·10 5

De·105 39.00 12.28 10.51 9.38 8.60 8.20 7.96 8.10 10.08 17.66 48.33

Da·1019 0.463 0.231 0.152 0.121 0.093 0.081 0.065 0.054 0.050 0.042 0.027

Dc·109 0.390 0.360 0.380 0.540 0.360 0.220 0.120 0.070 0.040 0.030 0.015

30 De·105 39.3 12.3 10.5 9.5 8.6 8.2 8.3 8.6 8.8 16.8 48.6

19

0.300 0.250 0.200 0.150 0.100 0.100 0.080 0.070 0.065 0.060 0.055

Da·10

Da·1019 0.463 0.231 0.152 0.121 0.093 0.081 0.065 0.054 0.050 0.042 0.027

Diffusion coefficients (m2/sec) at process temperature or, °C

39.00 30.00 20.00 13.50 12.00 7.00 5.50 4.40 4.20 5.59 13.00

De·10 5

Diffusion coefficients (m2/sec) at concentration of adsorbate in feedstock, wt. %

Dc·109 0.41 0.74 0.78 0.68 0.02 0.08 0.03 0.02 0.015 0.01 0.01

40

0.400 0.375 0.350 0.190 0.120 0.080 0.035 0.050 0.041 0.035 0.031

0.64 Dc·109

De·105 39.0 12.1 10.4 9.46 9.2 9.35 9.71 11.23 10.75 15.93 48.5

39.0 30.0 20.0 13.5 11.5 8.5 7.0 4.0 5.0 6.0 6.5

De·105

288

9 36 45 54 63 72 81 90 99 108 117

τ·10?2, sec

Table 4

0.495 0.470 0.435 0.420 0.300 0.225 0.170 0.125 0.080 0.066 0.051

Da·1019 0.640 0.635 0.590 0.480 0.360 0.270 0.215 0.130 0.065 0.040 0.025

0.195·10-3 Dc·109 39.9 32.0 20.0 14.5 12.0 8.5 7.0 6.0 4.5 6.8 12.5

De·105 0.492 0.465 0.431 0.415 0.290 0.210 0.165 0.121 0.070 0.060 0.048

Da·1019 0.630 0.625 0.580 0.475 0.340 0.255 0.200 0.125 0.050 0.035 0.020

0.834·10-3 Dc·109 39.6 31.4 18.0 12.5 11.0 8.0 6.5 5.8 4.2 6.4 11.8

De·105 0.488 0.461 0.428 0.405 0.280 0.205 0.161 0.118 0.064 0.056 0.045

Da·1019

Diffusion coefficients (m2/sec) at feedstock flow rate of, m/sec

0.623 0.600 0.560 0.457 0.325 0.250 0.187 0.120 0.045 0.031 0.014

0.340·10-3 Dc·109

38.9 30.7 17.1 13.4 12.0 7.5 6.2 5.3 3.8 5.6 10.9

De·105

Grade A aluminosilicate adsorbent with the following properties was used for the treatment: Bulk weight, g/cm 3 Granulometric composition, %

0.6-0.7

>0.8 mm 0.28-0.8 mm

5 95 ≤4

Specific humidity at 800°C, % Contaminant content, wt. %

≤0.2 ≤0.5

FeO B 2O3 Specific surface area, m 2/g Specific pore volume, m 3/g

22 0.4884

The process diffusion coefficients D a, Dc , D e were calculated with the algorithm in [5] for a concentration of aromatic hydrocarbons in the feedstock of 0.42-0.64 wt. %, process temperature of 20-40°C, and flow rate of the feedstock – 200-320°C fraction of liquid paraffin – of 0.195-1.340)×10-3 m/sec. The numerical values of these coefficients obtained are reported in Tables 2-4. They are essentially a function of the initial concentration of adsorbate in the feedstock and the feedstock temperature and flow rate. Their dependences were approximated with the equations: Da = 0.241⋅10 −19 e CTv Dc = 0.304 ⋅10 −9 e CTv De = 8.343 ⋅10 −5 e CTv

where C is the initial concentration of adsorbate in the feedstock, wt. %; T is the process temperature, K; ν is the feedstock flow rate, m/sec. The coefficients of the equations were found with the Matlab system in the Optimization Toolbox environment [6, 7]. The system of Eqs. (1)-(9) describing liquid-phase adsorption in a stationary bed of adsorbent, together with Eqs. (10)-(12), is thus a mathematical model of the dynamics of this process in nonequilibrium conditions. REFERENCES 1. N. V. Kel’tsev, Principles of Adsorption Technology [in Russian], Khimiya, Moscow (1984). 2. 3.

I. N. Taganov, Modeling of Mass and Energy Transfer Processes [in Russian], Khimiya, Leningrad (1979). V. A. Mironenko, Izv. Vyssh. Uchebn. Zaved., Geol. Razvedka, No. 11, 72-79 (1972).

4.

A. Zhilinskas and V. Shaltyanis, Searching for the Optimum: The Computer Expands the Possibilities [in Russian], Nauka, Moscow (1989).

5. 6.

F. V. Yusubov, R. I. Zeinalov, and Ch. Sh. Ibragimov, Zh. Prikl. Khim., 67, No. 5, 861-863 (1994). V. G. Potemkin, The Matlab System. A Manual [in Russian], Dialog-MIFI, Moscow (1997).

7.

V. G. Potemkin, The Matlab 5-x System of Engineering and Scientific Calculations [in Russian], Vol. 2, Dialog-MIFI, Moscow (1998).

289

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 4, 2007

CHEMMOTOLOGY

CHARACTERISTICS OF THE CHANGE IN THE PROPERTIES OF GASOLINES DURING STORAGE

O. Burkhan and I. M. Kolesnikov

UDC 665.633.25

The demand for gasolines with research octane numbers (RON) of 80, 90, 92, 95, and 98 is continuously increasing with the increase in the world fleet of vehicles with carburetor engines. The volume of the demand is more than 70% of the total demand for petroleum products. Commercial gasolines are usually manufactured by mixing different naphtha cuts with high-octane components of the type of oxygenates, aromatic concentrates, and additives of different chemical natures and applications. Naphtha cuts as components of commercial gasoline are manufactured in cat crackers, catalytic reforming (with and without hydrogen), coking and pyrolysis, thermal cracking, and visbreaking units [1]. Naphtha cuts containing no unsaturated hydrocarbons are only obtained in catalytic reforming of low-octane naphtha cuts on Pt, Re/g-Al 2O 3 catalysts. To create defined reserves of gasoline for different applications – automotive or aviation – are stored in above-ground, semi-underground, and underground tanks [2]. These reserves are necessary in case of disruptions in supplying gasoline for filling stations and for solving strategic and other problems. Gasolines in tanks are usually under an air cushion in which some amount of saturated water vapor can be present. Atmospheric oxygen is dissolved in liquid gasoline according to the Henry–Dalton law and diffuses over the entire volume by reacting with paraffins and alkylaromatic hydrocarbons, especially if the molecules of the latter compounds contain a tertiary hydrogen atom (for example, with isopropylbenzene), with formation of ____________________________________________________________________________________________________ I. M. Gubkin Russian State University of Oil and Gas. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 4, pp. 19 – 20, July – August, 2007. 290

0009-3092/07/4301–0290  2007 Springer Science+Business Media, Inc.

hydroperoxides. Hydroperoxides, which are highly reactive compounds, react with paraffins, yielding unsaturated hydrocarbons. In subsequent depletion in hydrogen, unsaturated compounds, together with aromatic hydrocarbons, undergo disproportionation, yielding gums and coke formations. The latter can be deposited on the walls or Table 1 Indexes

Density at 15°С, kg/m3 Distillation, °С IBP 10 % 50 % 90 % EP Content of resin, wt. % Octane number (RON) Density at 15°С, kg/m3 Distillation, °С IBP 10 % 50 % 90 % EP Content of resin, wt. % Octane number (RON) Density at 15°С, kg/m3 Distillation, °С IBP 10 % 50 % 90 % EP Content of resin, wt. % Octane number (RON) Density at 15°С, kg/m3 Distillation, °С IBP 10 % 50 % 90 % EP Content of resin, wt. % Octane number (RON)

Gasoline after storage lasting for, days 180 360 490

90 In southern region 735 740 743

670

745

747

749

42 60 100 150 187 0.03 90.5

before storage

42 59 86 159 173 0.5 90.3 In northern region 735 737

35 58 91 158 172 0.85 90.1

33 56 86 157 182 0.87 90

38 58 87 155 183 0.94 89.6

39 48 82 153 188 1.1 89.2

743

744

745

748

42 60 100 150 182 0.03 90.5

36 58 104 170 186 0.4 90.2 In eastern region 737

36 57 97 170 185 0.6 90

38 58 85 171 186 0.74 89.7

42 59 95 174 188 1.12 89.1

44 60 98 175 189 1.33 88.9

739

740

743

746

38 57 97 155 178 0.61 90

40 50 85 159 179 0.73 89.7

42 54 95 160 182 1.09 89.5

44 58 98 162 184 1.29 89.1

725

38 58 104 150 173 0.4 90.4 In central region 728

731

736

745

752

42 60 150 181 190 0.03 91.4

43 63 161 186 191 0.06 90.4

41 61 158 188 190 0.72 90

45 88 152 190 194 0.88 89.6

44 70 156 191 196 1.24 89.1

45 91 158 192 198 1.36 88.8

735 42 60 100 150 182 0.03 90.5

291

accumulate on the bottom of the tanks. In addition, the gums can be distributed in gasoline in the form of a disperse phase, turning it brown, i.e., worsening its color. A decrease in the isoparaffin and alkylaromatic hydrocarbon content will decrease the octane number of gasolines and alter their physicochemical properties. We investigated the characteristics of the change in the physicochemical properties of commercial gasoline* in prolonged storage in underground tanks in the southern, northern, eastern, and central regions of Syria. Samples of gasoline from different storage periods were collected from the tanks in the amount of 1 cm 3. Standard methods were used to determine their physicochemical properties. The initial gasoline contained 45% aromatic and less than 1% unsaturated hydrocarbons. The physicochemical properties were initially investigated after different storage times in tanks in the southern region. As the results of the studies reported in Table 1 show, the density increased from 735 to 749 kg/m 3 , the octane number decreased from 90.5 to 89.2, and the gum content increased from 0.03 to 1.1 wt. % with an increase in the duration of storage of the gasoline. At the end of two years of storage, the quality of the gasoline thus worsened. It was necessary to add additives or reformate with a RON within the limits of 92-94 to restore the gasoline. The characteristics of the change in the physicochemical properties of the gasoline stored in underground tanks in the north of the country persisted (see Table 1): with an increase in the storage time, the density increased from 735 to 748 kg/m 3 , the gum content increased from 0.03 to 1.33 wt. %, and the octane number decreased, but slightly less significantly – by 1.7 point. To restore the octane number, it was necessary to add antiknocks or high-octane reformate (or aromatic concentrates) to the gasoline. In storage of gasoline in underground tanks in the east of the country, its physicochemical properties changed more slowly (see Table 1), but the characteristics of the change were the same: the octane number decreased, and the density and gum content increased. In the tanks located in the central region of the country, the characteristics of the change in the physicochemical properties of the gasoline in prolonged storage were also the same. However, the decrease in the octane number and increase in the density and gum content were more important in this region in comparison to the others. This was due to the higher average annual temperature in this region and consequently heating of the upper layer of gasoline. The degree of its oxidation increased as a result, and disproportionation with accumulation of gums and a decrease in the isoparaffin content began to take place. In storing gasolines in underground tanks in different regions of Syria, the characteristics of the change in their physicochemical properties were thus qualitatively the same. However, the octane number and density, as well as distillation of the gasolines, changed more significantly in the central region of the country. REFERENCES 1. A. Abugri, Candidate Dissertation, M. M. Gubkin Moscow Institute of Oil and Gas, Moscow (1986). 2.

V. A. Mazurov, Underground Gas and Oil Depots in Rock Salt Deposits [in Russian], Nedra, Moscow (1982).

*Obtained at the oil refinery in Baniyas. 292

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 4, 2007

SYNERGISM BETWEEN MC-MA-MCNR2 TERPOLYMER AND EVA AS A COLD FLOW IMPROVER IN DIESEL FUEL Yuping Song,1 Chao Qiu,1 Xiaohong Xu,2 Xisheng Fu,2 and Tianhui Ren1*

A novel terpolymer, MC-MA-MCNR 2, derived from tetradecyl methacrylate (MC), maleic anhydride (MA), and methacrylamide (MCNR 2 ) was synthesized. The ability of MC-MA-MCNR 2 was evaluated as a cold flow improver in diesel fuel, and the interactions of MC-MA-MCNR 2 with several kinds of copolymer were studied. To provide a better understanding of the synergistic mechanism, microscopy was used to study the crystal conformation when MC-MA-MCNR 2 and EVA (ethylene-vinyl acetate) are mixed into a diesel fuel. The results indicate that using blends of MC-MA-MCNR 2 and EVA, one can obtain a satisfactory cold filter plugging point depression. Based on the microscopy experiment, the synergism mechanism was discussed. Several techniques have been used to minimize the problems caused by wax deposition in diesel fuel, and the continuous addition of a polymeric modifier such as ethylene-vinyl acetate copolymer, acrylate copolymer, and their derivatives is considered an attractive technological alternative due to its simplicity and economy [1-4]. In most cases two or even three component additives are used for improving both flowability and filterability currently [5-9], but the relationship between the structure and the property of these polymer additives and the synergism mechanism of these additives is rarely reported, and the interaction between the cold flow improvers and the wax is still an interesting theme of scientific research at present. In this paper, a novel cold flow improver, MC-MA-MCNR 2, was synthesized and evaluated. Several different molecular structure copolymers were mixed with MC-MA-MCNR 2, these mixtures were evaluated as cold flow improvers in diesel fuel, and the synergism mechanism of MC-MA-MCNR 2 and EVA was studied. The electron microscopy work by transmission electron microscopy (TEM) presented in this paper is an “in situ” investigation on the morphology of wax crystal in diesel fuel at low temperatures. Microscopy was performed ____________________________________________________________________________________________________ 1 School of Chemistry & Chemical Engineering, Shanghai JiaoTong University, Shanghai 200240, P. R. China. 2Petrochina Lanzhou Lubricating Oil R&D Institute, Lanzhou 730060, P. R. China. *Corresponding Author: e-mail: [email protected], Fax: 86-021-54741297, Tel: 86-021054747118. Published in Khimiya i Tekhnologiya Topliv i Masel, No. 4, pp. 21-23, 2007. 0009-3092/07/4301–0293  2007 Springer Science+Business Media, Inc.

293

Table 1. Physicochemical Characteristic of the Basic Diesel Fuels Indexes

Specification

Disel fuel

SH/T 0604

841.9

Kinematic viscosity at 20°C, mm /s

GB/T 265

4.524

Flash point, °C

GB/T 261

67

Cold filter plugging point (CFPP), °C

SH/T 0248

1

Pour point (PP), °C

GB/T 3535

-5

Solid point (SP), °C Group hydrocarbon content, wt.%

GB/T 510

-6

saturated

MS

73.4

aromatic

MS

26.6

n-paraffins

GC

41.27

Specific gravity at 20°C, kg/m

3 2

Average carbon number

GC

Distillation range, °C

GB/T 6536

15.7 174 – 356

Table 2 Results for the Diesel Fuel Blended with Mixtures of MC-MA-MCNR 2 and Other Copolymers Blended additives

No.

Mixture ratio, ppm

∆SP, °C

∆CFPP, °C

2

1

MC-MA-MCNR

500

20

1

2

MC-MA-MCNR2 : PIBMA

400:100

18

2

3

MC-MA-MCNR2 : PIBA

400:100

12

1

4

MC-MA-MCNR2 : PIB

400:100

15

1

400:100

24

5

MC-MA-MCNR

5

2

Table 3. Results of Diesel Fuel Blended with MC-MA-MCNR2 and EVA in Different Amounts No.

MC-MA-MCNR2 : EVA (mass)

∆SP, °C

∆CFPP, °C

1

100:400

36

9

2

300:200

23

12

3

400:100

24

11

4

500:0

20

1

to provide a better understanding of the synergism with respect to the cold filter plugging point when MC-MA-MCNR 2 and EVA cold flow improvers are mixed into a diesel fuel. A terpolymer derived from tetradecyl methacrylate, maleic anhydride, and methacrylamide, MC-MA-MCNR 2, was synthesized in the laboratory by radical polymerization in solution at atmospheric pressure [10]. Polyalkenylsuccinimide (PASI) was also synthesized in the laboratory [11]. Ethylene-vinyl acetate (EVA) copolymer synthesized in the laboratory by LanZhou Chemicophysics Research Institute was used. Polyisobutylene amide (PIBA) and polyisobutylene (PIB) used in these experiment are of technical grade. The diesel fuel derived from blended crude oils from different oil reserves in Xinjiang, P.R. China was used as the basic diesel fuels for evaluating the cold flow performance of the above-mentioned additives. Its physicochemical characteristics are listed in Table 1. The data indicate that the carbon number distribution of the

294

total n-alkanes in the diesel fuels is wide and the amount of high molecular weight n-alkanes in the diesel fuel is higher. The cold flow performance, solid point depression (∆SP) and cold filter plugging point depression (∆CFPP), of the tested diesel fuel samples was determined according to SH/T0248 and GB/T 510. The solid point depression was determined by a BLY solid point instrument. The method of SH/T0248 is similar to the method of IP 309. The diesel fuels mentioned above were observed under the same temperature conditions by TEM. The observations were performed on samples allowed to gel at –2°C (in the refrigerator) below the cold flow plugging point of the diesel fuel untreated with additives for 24 h. A drop of the sample was taken by microsampling and placed into the holder, which has the shape shown in Fig. 1 and which is made of copper. The same type of holder was used for all samples, with diameters of 1.5 mm. After the sample was put into the holder, the holder was submerged into liquid nitrogen to guarantee fast freezing with the aim of fixing the structure by keeping the initial, unfrozen, texture [12]. After several minutes, the holder was put into the Hitachi HUS-5GB equipment to fracture, mount, replicate, clean and put on the 400 mesh copper grid [13]. The transmission electron microscope is a Hitachi H-600 at 75 kV. The microscope is equipped with a tungsten filament. The effect of concentration of the cold flow improver (MC-MA-MCNR 2) on efficiency in terms of solid point depression and cold filter plugging point depression was studied. The tested diesel fuels were also doped individually with concentrations 100, 200, 300, 400, and 500 ppm of the cold flow improver. The doped samples were subjected to “SP and “CFPP determination. The results are presented in Fig. 2. The data presented in Fig. 2 show that MC-MA-MCNR 2 affects the cold flow property in such a way that with increasing concentration of MCMA-MCNR 2 , “SP increase and “CFPP decrease. MC-MA-MCNR 2 has almost no effect on the cold filter plugging point depression of the diesel fuel and brings about a small solid point depression.

1.5 mm Fig. 1. Sample holder for cryofixation.

∆SP, ∆CFPP , deg

20 15 10 5

1

1

1

1

1

2 2

2

2

2

0 100 200 300 400 500 Content of MC-MA-MCNR M, ppm 2

Fig. 2. Effect of concentration of MC-MA-MCNR 2 on ∆SP and ∆CFPP of diesel fuel. 295

The cold flow performance of a series of diesel fuel blended with mixtures of MC-MA-MCNR 2 and other copolymers was evaluated. The results are listed Table 2. It can be seen that diesel fuels blended with mixtures of MC-MA-MCNR 2, PIBMA, PIBA, and PIB show slightly antagonistic behaviors, whereas diesel fuel blended with a mixture of MC-MA-MCNR 2 and EVA demonstrate very good synergistic action. This is because a cold flow improver only needs to be slightly polar rather than nonpolar or highly polar. When polar groups are present in excess in the molecule, they prevent the polymer from co-crystallizing with the chains of n-paraffins in diesel fuel [14]. There is a high content of polar groups in the structure of PIBMA, PIBA, and MC-MA-MCNR 2 polymers, so antagonistic behaviors arise when the diesel fuel is blended with mixtures of MC-MA-MCNR 2 , PIBMA, and PIBA. On the other hand, there are so many side chains in PIBMA, PIBA and PIB that they prevent the polymer from co-crystallizing with the chains of n-paraffins in the diesel fuel. The cold flow performance of the mixed additives (EVA and MC-MA-MCNR 2 were mixed at different ratios) was evaluated in the diesel fuel. The results are listed in Table 3 and Fig. 3. It is clear that the mixed additives are more efficient in cold filter plugging point depression than MC-MA-MCNR 2 alone. The data in Table 3 and Fig. 3 show that when the EVA concentration increases in the mixed additives, ∆SP increases, and ∆CFPP increases until a certain concentration is reached, above which ∆CFPP starts to decrease. An optimal

a

b

c

d

Fig. 3. Effect of ratio of MC-MA-MCNR 2 to EVA on the ∆SP and ∆CFPP of diesel fuel. Transmission electron micrographs of the diesel fuel: a – untreated with additives at –2°C; b – doped with MC-MA-MCNR2 at –2°C; c – doped with EVA at –2°C; d – doped with mixture of MC-MA-MCNR 2 and EVA (4:1) at –2°C. 296

formulation was found: 300 mg kg -1 of MC-MA-MCNR 2 plus 200 mg kg -1 of EVA. A lowering (12°C) of CFPP was obtained, and also a lowering (23°C) of SP. It is known that the morphology of the wax crystals is an important aspect in the study of the interaction mechanism between the cold flow improver and the wax in the diesel fuel. In this paper the photomicrographs of the wax crystals in the diesel fuels untreated and treated with the above-mentioned additives were taken at low temperatures. The wax crystals conformation of the diesel fuel and samples doped with MC-MA-MCNR 2, EVA, and the mixture of MC-MA-MCNR 2 and EVA are shown in Fig. 3. It can be seen in Figs. 3a and 3b that the crystal conformations are very similar, which indicates that the addition of MC-MA-MCNR 2 has no effect on the co-crystallization of waxes in the diesel fuel and results in a small change in the cold filter plugging point. Figure 3b shows that the wax crystals are spherical. The diameters of the crystal particles are not uniform and vary from 40 to 340 nm. The picture shows the crystal particles stacked together. Figure 3c clearly shows that the crystal particles are spherical too. The diameters of the crystal particles are small, 40-80 nm. The crystal particles are dispersed but not well proportioned. The sizes of the crystals are similar. Figure 3d shows that the diameters of the crystals are not uniform; the biggest crystal particles are 120 nm, and most of the crystal particles are 30-40 nm. Though the sizes of the crystals are not very similar, the crystal particles are dispersed homogeneously. It is reported that the interaction of the n-paraffins with the cold flow improver takes place by a co-crystallization mechanism [15]. The additive serves as a nucleation site for wax precipitation; at the same time it plays an important role in dispersing the wax. The nucleation and dispersity properties of the cold flow improver depend mainly on its molecular structure. Based on the observations, it can be concluded that EVA possesses good nucleation properties, a n d M C - M A - M C N R 2 o n l y p o s s e s s e s g o o d d i s p e r s i o n p r o p e r t i e s . E VA i s e t h y l e n e - v i n y l a c e t a t e , and MC-MA-MCNR 2 is a long-chain alkyl methacrylate, maleic anhydride, and methacrylamide (MC-MA-MCNR 2) terpolymer. The structure of EVA and MC-MA-MCNR 2 formulations is as follows:

C14H29

RN

Because the content of polar group in MC-MA-MCNR 2 is higher than EVA, the terpolymer possesses higher dispersibility. In other words, polar atoms in the molecule hinder co-crystallization of the chains of n-paraffins in diesel fuel. At the same time, polarity prevents MC-MA-MCNR 2 from co-crystallizing with the nalkane to form small-particle wax crystals. On the other hand, the side chain of EVA does not contain polar atoms such as oxygen, nitrogen, etc., so EVA can co-crystallize with the n-alkane to act as a nucleation center. When the

297

two additives are mixed and used in diesel fuel as a cold flow improver, they show good nucleation and dispersity properties and result in satisfactory depression of the solid point and cold filter plugging point. The results reported here provide a basis for an explanation of the antagonism in diesel fuel doped with two different additives. The size and shape of n-alkane crystals are different when MC-MA-MCNR 2 and EVA are added to the diesel fuel.MC-MA-MCNR 2 develops well-separated crystals, but they are larger than in the undoped diesel fuel;the EVA additive always produces the same behavior: very small crystals (40-80 nm) are observed. Using blends of MC-MA-MCNR 2 and EVA, a small crystals size is obtained, well-separated crystals are observed, and therefore the ∆CFPP increases. The synergism appears to depend on a modification of the chemical structure of the two additives or optimization of the concentration of each component of the blend. REFERENCES 1. Nesh A. Kidd, U.S. Patent 4,362,533, Dec. 7, 1982. 2. 3.

Maged G. Botros, U.S. Patent 5,681,359, Oct. 28, 1997. I. M. EI-Gamal, T. T. Khidr, and F. M. Ghuiha, Fuel, 77, No. 5, 375-385 (1998).

4. 5.

I. M. EI-Gamal, T. T. Khidr, and F. M. Ghuiha, Fuel, 76, No. 14/15, 1471-1478 (1997). D. V. Gabriele, O. F. Kunt, R. Joachim, H. Heinrich, and W. Bernd, German Patent, DE4410196 A1, Sep. 28, 1995.

6. 7.

I. Takaharu, N. Takeshi, and Y. Shingo, Eur. Pat.085803A1, Sep. 27, 1982. N. Feldman, U.S. Pat. 4,211,534, July 8, 1980.

8. 9.

C. J. Dorer, Jr. and K. Hayashi, U.S. Pat. 4,623,684, Nov. 18, 1986. Mc. A. Matthew, T. R. Dryden, and I. Tuncel, PCT Patent WO 91/11469, Aug. 8, 1991.

10. Yuping Song, Tianhui Ren, Xisheng Fu and Xiaohong Xu, in press. 11. Patrick Gateau, Dariel Binet, Fabrice Paille, and Jean-pierre Durand, U.S. Pat. 5,735,915, Apr. 7, 1998. 12. Henry S. Ashbaugh, Aurel Radulescu, Robert K. Prudhomme, Dietmar Schwahn, Dieter Richter, and Lewis J. Fetters, Macromolecules, 35, 7044-7053 (2002). 13. Moussa Kane, Madeleine Djabourov, Jean-Luc Volle, Jean-Pierre Lechaire, and Ghislaine Frebourg, Fuel, 82, 127-135 (2003). 14. R. Berkhof and H. J. Kwekkeboom, Reprint, 3rd Servo Oil Field Chemicals Symposium, Moscow, USSR, Octember, 1985. 15. G. A. Holder and J. Winker, J. Inst. Petrol. (London), 51, No. 499, 241, (1965).

298

Chemistry and Technology of Fuels and Oils, Vol. 43, No. 4, 2007

FEATURES OF AGING OF ENGINE OIL IN A GAS ENGINE

D. V. Boikov, T. B. Bugai, and Yu. P. Mal’kov

UDC 621.433:621.892.002.25

The basic physicochemical indexes of M-10-D 2(m) engine oil change much less intensively in a gas engine than in a diesel. Low accumulation of elements – indicators of parts wear – and fouling of parts by carbon and varnish deposits were noted. Formation of ash deposits in the valves was more important. Dithiophosphate additives were depleted similarly in both engines. Information on the requirements for special oils for gas engines is reported The YaMZ-831.10 engine that runs on natural gas (methane) as fuel was created at Avtodizel’ Co. based on the YaMZ-238M2 engine. The new engine has a number of original elements and units that ensure optimum operation in the gas mode. In particular, a carburetion ejector system and electric-spark ignition with a microprocessor control system were used. The design of the cylinder heads was altered to install the electric spark plugs, the combustion chamber in the piston under a degree of compression of 11.5 was enlarged, etc. The engine is designed for operating in stationary conditions in different generating sets. It is powered from the industrial gas system. The pressure of the gas entering the reducer is 0.07-0.13 mPa. Converting an engine to gas fuel causes a number of features of aging of the oil. In operating YaMZ-236Yu diesels in the gas-diesel mode, this process is slowed significantly [1]. However, the design difference in gas-diesel (dual-fuel) engines from ordinary engines is insignificant. The fuel is ignited by an ignition portion of diesel fuel, whose consumption is 20-25% of gas consumption. These engines can be easily switched to operate on diesel fuel alone. Due to the design features, the advantages of using gas fuel cannot be completely implemented in them. Operation of specially developed gas engines that only operate on gas fuel is associated with high temperatures since a stoichiometric mixture of methane and air has a higher (by 1.22 time) heat of combustion in ____________________________________________________________________________________________________ Avtodizel’ OJSC, Yaroslav Engine Plant. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 4, pp. 24 – 27, July – August, 2007. 0009-3092/07/4301–0263 © 2007 Springer Science+Business Media, Inc.

299

ACEA E3-93 – – – –

API CE, CF-4, SF, SH

М-3271-1 RGD None – – –

ACEA E3 ACEA А2-96 Е2-93 API CF-4/SF

level of performance properties, km

DAF MAT 70310 Page 226.9 None

Specification

Notes. * High-temperature viscosity at high shear rate. ** Change time: 30,000 km *** Change time: 50,000 km, sampling: 15,000 km.

RVI Volvo Caterpillar Superior Dresser-Rand

MAN

DAF Daimler- Chrysler IVECO

Equipment manufacturer

– 150 000*** – – Tests required

90 000**

2×40 000 – –

duration of performance test, km

vaporizability: maximum loss, % – – – – –

13

15 13 –

HTHS,* MPa⋅sec – – – – –

3.5

– 3.5 –