Green Chemistry: Research and Connections to Climate Change 9783110745658, 9783110745603

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Mark Anthony Benvenuto and Lindsey A. Welch (Eds.) Green Chemistry Green Chemical Processing

Green Chemical Processing

Edited by Mark Anthony Benvenuto

Volume 10

Green Chemistry

Research and Connections to Climate Change Edited by Mark Anthony Benvenuto and Lindsey A. Welch

Editors Prof. Dr. Mark Anthony Benvenuto Department of Chemistry and Biochemistry University of Detroit Mercy 4001 W. McNichols Rd. Detroit, MI 48221-3038 USA [email protected] Prof. Lindsey A. Welch Department of Chemical, Physical, and Forensic Sciences Cedar Crest College 100 College Drive Allentown PA 18104 USA [email protected]

ISBN 978-3-11-074560-3 e-ISBN (PDF) 978-3-11-074565-8 e-ISBN (EPUB) 978-3-11-074568-9 ISSN 2366-2115 Library of Congress Control Number: 2023936223 Bibliographic information published by the Deutsche Nationalbibliothek The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the internet at http://dnb.dnb.de. © 2023 Walter de Gruyter GmbH, Berlin/Boston Cover image: scyther5/iStock/Thinkstock Typesetting: Integra Software Services Pvt. Ltd. Printing and binding: CPI books GmbH, Leck www.degruyter.com

This volume is dedicated to George Ruger, a tireless advocate for green chemistry. Taken too soon.

About the series Green Chemical Processing is a continuing series of volumes composed of refereed chapters, with upcoming volumes having submission dates of 15 June and 15 December each year. All areas of green chemistry, pending as well as established, are considered and welcome. If you are interested in contributing a chapter, please contact series editor Mark Benvenuto of the University of Detroit Mercy at: [email protected] concerning the appropriateness of your topic. We are interested in any and all new ideas that examine any of the 12 principles of green chemistry. For more information on all previous and upcoming volumes of Green Chemical Processing, see https://www.degruyter.com/view/serial/GRCP-B

https://doi.org/10.1515/9783110745658-202

Contents About the series

VII

List of contributing authors

XI

H. N. Cheng 1 Use of green chemistry for process development and improvement

1

Ashutosh Negi, Md. Aasif Jawed, Md. Imteyaz Alam, M. Ali Haider, S. Fatima, Ejaz Ahmad 2 Technoeconomic evaluation and life cycle assessment of biorenewable route to produce high-value aromatics 13 Awais Ahmad, Rafael Luque 3 Green chemistry and catalysis

33

Mara R. Livezey 4 Green chemistry and environmental justice in the biochemistry classroom 45 Mythreyi Sivaraman, Cole Radke, Weile Yan 5 Quantifying microplastics in beach sand and river sediment using thermal analytical methods 53 Lindsey A. Welch 6 Outlook of undergraduate programs in sustainability and environmental studies in the United States 75 Paul Martin, Heinz Plaumann 7 Likely energy solutions for reversing climate change

83

Renee Trotmann, Mark Benvenuto 8 Carbon dioxide, climate change, and classroom connections Index

101

95

List of contributing authors H. N. Cheng Southern Regional Research Center USDA Agricultural Research Service New Orleans LA 70124 USA Email: [email protected] Ashutosh Negi Renewable Energy and Chemicals Laboratory Department of Chemical Engineering Indian Institute of Technology Delhi New Delhi 110016 India And School of Interdisciplinary Research Indian Institute of Technology Delhi New Delhi 110016 India And Centre for Automotive Research and Tribology Indian Institute of Technology Delhi New Delhi 110016 India Md. Aasif Jawed Department of Chemical Engineering Aligarh Muslim University Aligarh 202002 India Md. Imteyaz Alam Department of Chemistry University of Milan Via Camilo Golgi, 19 Milan 20133 Italy Email: [email protected] M. Ali Haider Renewable Energy and Chemicals Laboratory Department of Chemical Engineering Indian Institute of Technology Delhi New Delhi 110016 India

https://doi.org/10.1515/9783110745658-204

S. Fatima Centre for Automotive Research and Tribology Indian Institute of Technology Delhi New Delhi 110016 India Ejaz Ahmad Department of Chemical Engineering Indian Institute of Technology (Indian School of Mines) Dhanbad Dhanbad 826004 India Email: [email protected] Awais Ahmad Departamento de Quimica Organica Universidad de Cordoba EdificioMarie Curie (C-3) Ctra Nnal IV-A, Km 396 E14014 Cordoba Spain Rafael Luque Departamento de Quimica Organica Universidad de Cordoba EdificioMarie Curie (C-3) Ctra Nnal IV-A, Km 396 E14014 Cordoba Spain Email: [email protected] Mara R. Livezey Department of Chemistry and Biochemistry University of Detroit Mercy Detroit MI 48221 USA Mythreyi Sivaraman Department of Civil and Environmental Engineering University of Massachusetts Lowell Massachusetts USA

XII

List of contributing authors

Cole Radke Department of Civil and Environmental Engineering University of Massachusetts Lowell Massachusetts USA Weile Yan Department of Civil and Environmental Engineering University of Massachusetts Lowell Massachusetts USA Email: [email protected] Paul Martin Spitfire Research Toronto, Ontario, Canada

Heinz Plaumann Wayne State University Detroit MI 48202 USA Lindsey A. Welch Department of Chemical Physical and Forensic Sciences Cedar Crest College Allentown PA 18104 USA

H. N. Cheng

1 Use of green chemistry for process development and improvement Abstract: Sustainable green chemistry has attracted a lot of attention, and publications in this area have notably increased in recent years. One of the areas of opportunity is to develop green chemical processes and eco-friendly products that will prevent pollution and create alternatives to hazardous substances. These processes should be based on the green chemistry principles and can be either new or improved. The author has been fortunate to have worked in this area for many years. As a member of the ACS Presidential Succession in 2020–2022, he has also adopted sustainable green chemistry as one of his platforms. In this chapter, drawing exclusively from previously published papers and patent publications, the author describes several chemical and polymeric studies as examples of new or improved processes inspired by green chemistry and sustainability. These include enzymatic processes, use of microwave, ecofriendly and nontoxic solvents, reduced use of strong acids, and chemical reagents for pulp and paper.

1.1 Introduction In 2015, the United Nations General Assembly approved the 17 Sustainable Development Goals (SDGs), designed to be a blueprint to achieve a better and more sustainable future for all people and the world by 2030 [1]. These goals aim to improve health and education, reduce inequality, and spur economic growth, while tackling climate change and working to preserve our environments, oceans, and forests. The SDGs are highly desirable in order to preserve the qualities of life on this planet and represents an investment in our future. From the viewpoints of the American Chemical Society (ACS) [2], chemistry and chemistry-related activities can help in at least seven of these goals: (1) zero hunger; (2) good health and well-being; (3) clean water

Acknowledgments: The author would like to thank all his collaborators over the years for the publications cited in this chapter. Thanks are also due to Matt McBride at CAS (a division of ACS) for supplying the data that were used to prepare Figure 1.1. Mention of trade names or commercial products is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA. USDA is an equal opportunity provider and employer. Note: This is a contribution to the book series on Green Processing Methodologies (edited by Mark Benvenuto and Lindsey Welch). This book will be published by De Gruyter. H. N. Cheng, Southern Regional Research Center, USDA Agricultural Research Service, New Orleans, LA 70124, USA, e-mail: [email protected] https://doi.org/10.1515/9783110745658-001

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H. N. Cheng

and sanitation; (4) affordable and clean energy; (5) industry, innovation, and infrastructure; (6) responsible consumption and production; and (7) climate action. Green chemistry is a major part of sustainability. According to the U.S. Environmental Protection Agency, green chemistry aims to design and produce cost-competitive chemical products and processes that attain the highest level of the pollution-prevention hierarchy by reducing pollution at its source [3, 4]. Indeed, the practice of green chemistry can minimize pollution, reduce waste, minimize use of materials, and reduce hazards and risks. Moreover, good health and well-being can be promoted by using safer chemicals, reducing chemical hazards, and minimizing accidents. The design for energy efficiency and the use of catalysts can decrease energy usage and help climate action. The adoption of atom economy, use of renewable feedstocks, and design for degradation can reduce environmental problems, such as waste disposal, microplastics, and air and water pollution. Judicious applications of green chemistry principles should slow down the depletion of world’s limited resources due to increasing population and industrial activities [5–7]. Since the 12 principles of green chemistry [4] were developed in 1998, there has been increasing interest from industry and research communities to adopt the green chemistry practices. The formulation of SDGs in 2015 has raised public awareness and stimulated further activities. Already many companies have announced their goals to achieve some aspects of sustainability, and further industrial adoption may be forthcoming [5]. The increased research activities in this area can be seen from the trends in the publications. Figure 1.1 provides the number of papers in the CAS database that included “sustainable” or “sustainability,” and “green chemistry” in their titles or abstracts in the period 1970–2021. The number of papers with “green chemistry” increased rapidly after 2000; the papers with “sustainability” also showed roughly the same trend but increased even more rapidly after 2015.

Figure 1.1: Number of papers published with “sustainable” or “sustainability,” and “green chemistry” in the titles or the abstracts in the period 1970–2021 (courtesy of Matt McBride at CAS, September 1, 2021).

1 Use of green chemistry for process development and improvement

3

Whereas the increased publication activities in sustainability and green chemistry are favorable trends, the commercial success of green chemistry depends on the economic benefits of green products and processes relative to conventional approaches. The economic issue is especially important when a conventional product is directly substituted by a greener alternative. Sometimes, government incentives and/or regulatory requirements for products or process safety can provide the impetus needed for the adoption of the greener alternative, but this is only a partial solution. It is more desirable to develop and implement green products and processes that are more cost-effective relative to the existing products and processes. Of course, if opportunities can be found for products or processes that represent new applications or new markets, these would surely be highly attractive. As a member of the ACS Presidential Succession in 2020–2022, the author has adopted sustainable green chemistry as one of his presidential platforms [8]. In the past 25 years, he has also been fortunate to have carried out some of his research efforts in sustainable green chemistry in industry and at the Southern Regional Research Center of USDA-ARS. Part of this work has been previously published in journals and patent publications. In this chapter, a review is made of previously published works, particularly highlighting the combined use of organic, physical, and polymer chemistry in the sustainable green chemistry context.

1.2 Enzymatic processes One of the 12 principles of green chemistry is catalysis [3, 4]. The idea is that catalytic reagents are superior to stoichiometric reagents, and they can enhance the product yield and/or the selectivity of a reaction. A promising development in sustainable green chemistry is the use of biocatalysts (such as enzymes and microbes) for organic and polymeric reactions [9–17]. Enzymes, in particular, are mostly proteins obtained from living organisms that are biodegradable and nontoxic. They often work in aqueous solvents at lower reaction temperatures than metallic and organic catalysts, thereby reducing solvent hazards and saving energy. Many enzymes are highly specific and act on only certain substrates; in this way, the reactions catalyzed by these enzymes produce less by-products and wastes. Some enzymes are stereospecific and can be used to prepare products with specific optical activities. Other enzymes are less specific and can accept different types of substrates. Innovations are possible when new substrates or enhanced reactivity/selectivity is found for an enzyme, or when an enzyme is modified genetically or chemically to provide improved cost versus performance. There has been widespread use of enzymes for organic, biochemical, and polymer reactions [9–17]. An example is shown for the reaction of starch with alkyl ketene dimer, which produced a new type of hydrophobically modified starch (Figure 1.2) [18].

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H. N. Cheng

O Starch – OH +

O

O Lipase

O

Starch–O

Figure 1.2: Reaction of starch and alkyl ketene dimer (AKD) to form hydrophobically modified starch in the presence of a lipase enzyme.

The reaction took place in a polar aprotic solvent with heating and stirring. It was facilitated with the use of a lipase enzyme, which gave products with higher degrees of substitution (DS) at lower temperatures [18]. A comparison of the reaction with or without the enzyme is shown in Table 1.1. This hydrophobically modified starch had improved polymeric properties as compared to the original starch and may be used as a thickener or an emulsifier. Enzymatic processes were also reported to permit the formation of water-soluble polyamides, and some of which were difficult to do without enzymes [19, 20]. Other enzyme-catalyzed reactions and processes involving the author and his collaborators have been reported in books and review articles [8, 11, 14, 16]. Table 1.1: Comparison of enzymatic and chemical synthesis of starch–AKD (alkyl ketene dimer) derivatives. Method

With enzyme

Without enzyme

AKD used Temperature Acid/base used Starch degradation Product viscosity

 wt% – °C None No degradation Higher

Excess AKD used – °C NaOH addition helps Partly degraded Lower

1.3 Use of microwave The use of microwave energy is known to speed up the heating of objects and is increasingly applied to a variety of chemical processes. This is a good tool for use in sustainable green chemistry because faster reactions can save time and energy and potentially reduce the exposure to chemical reagents. In an effort to convert agrobased materials to useful products, the author and his collaborators have found microwave to be valuable for many processes. An example of polyurethane formation between toluene diisocyanate (TDI) and sucrose is shown in Figure 1.3. This reaction involved dissolving sucrose and TDI in N,N-dimethylformamide and heating the mixture [21]. As shown in Table 1.2, it took 20 min of conventional heating at 145 °C to achieve 47% yield. With microwave heating, the same yield was achieved after 6 min

1 Use of green chemistry for process development and improvement

OCN

NCO

DMF

+ sucrose

(

O

O

OC NH

NH C O

sucrose

5

(n

∆

CH3

Figure 1.3: Reaction of TDI and sucrose to form polyurethane. Table 1.2: Polymerization reaction involving TDI and sucrose at 145 °C, using 1 g of sucrose and 0.364 g TDI in 5.5 g N,N-dimethylformamide. Heating mode Conventional Microwave Microwave Microwave

Heating time (min)

Product yield (g)

Yield (%)

   

. . . .

   

[21]. The NMR spectra for the two products (not shown) were identical. Thus, microwave heating saved time and energy relative to conventional heat. In another example, soybean oil [22, 23] was found to react with diethyl azodicarboxylate to form ene and Diels–Alder products, which exhibited enhanced viscosity. In that reaction, microwave heating also provided a shorter reaction time than conventional heat. Microwave was also found to facilitate the synthesis of alkyl cellulose in aqueous medium [24]. In addition to polymer reactions, microwave technology has been employed for the extraction of phenolic antioxidants from common beans [25, 26]. The extraction efficiency was found to depend on a number of factors, including bean type, tissue type (hull or cotyledon), solvent used, extraction temperature, and extraction time. Microwave extraction was found to be preferred for extraction with water and ethanol, but conventional heat was better with 1:1 ethanol–water mixture.

1.4 Ecofriendly and nontoxic solvents Another principle of green chemistry is to use safer solvents or to avoid them altogether. In view of this need, the author and his collaborators have designed and eliminated organic solvents in several of their reactions. For example, in the synthesis of poly(aminoamides) [27] and new polyamide structures based on methyl acrylate and diamine [28], no solvents were involved, and the reactions occurred in bulk. Likewise, in xylan acetylation, the reactants (xylan, acetic anhydride, and a catalyst) were heated at 60–110 °C for 6 h, and no solvent was used [29]. In the synthesis of novel iron-containing ionomer [30], two procedures were used, one involving tall oil fatty

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acid (TOFA), iron powder with carbon dioxide, and a small amount of water, and the second procedure involving TOFA, steel dust or iron powder, and carbonated water at 35–45 °C. No organic solvents were involved in either case. One of the common processes employed in food processing is the extraction of specific substances from agro-based raw materials. However, organic solvents often pose health hazard and pollute the air. A promising green alternative is the natural deep eutectic solvents (NADES) [31–33]. A NADES solvent contains two or three natural, renewable, and biodegradable natural components, which form a eutectic mixture because of selfassociation and/or specific interactions among the components. For this eutectic mixture, the melting point is lower than the melting points of the individual components; the NADES of interest are those eutectic mixtures that are liquids at 25–100 °C. Examples of NADES include mixtures of natural materials like simple sugars (glucose and fructose), low-molecular-weight acids (malic, citric, and lactic acids), choline chloride, and urea. In a recent work, NADES was used as a green alternative to alcohol to extract soluble sugars from ripe bananas [34]. Thirty NADES mixtures were characterized and screened, and four of them were selected as most appropriate (Table 1.3). Water was added to NADES as shown in Table 1.3 to reduce viscosity, and microwave was used to enhance extraction. Thus, the combination of NADES, water addition, and microwave represented an improved methodology for the extraction of polar compounds from agro-based raw materials [34]. This work covered three green chemistry principles: (1) safer solvents, (2) use of renewable feedstocks, and (3) design for energy efficiency. The use of NADES satisfied the first two principles, and the use of microwave (with the reduction in reaction time) satisfied the third principle. Table 1.3: Composition of the NADES systems selected for extraction of soluble sugars from ripe bananas. Component  Component 

Component  Molar ratio Temperature (°C)

Malic acid Malic acid Citric acid Citric acid

Water Water Water Water

Choline chloride β-Alanine Choline chloride β-Alanine

:: :: :: ::

   

1.5 Reduced use of strong acids Cellulose acetate is a well-known industrial product with many commercial applications. It is typically made from wood pulp through reaction with acetic acid and acetic anhydride in the presence of sulfuric acid to form cellulose triacetate, which is then partially hydrolyzed to the desired degree of substitution [35]. As the handling of sulfuric acid can be hazardous, it would be useful to replace it with an alternative. A

1 Use of green chemistry for process development and improvement

7

possibility is to use iodine instead [36, 37]. In this way, different types of cellulose esters have been prepared [38, 39]. Another alternative is to use Lewis acid catalysts, like metal chlorides. The reactions were conducted on 0.5 g starch, 1 g acetic anhydride, 0.05 g catalyst, and 6 h reaction time. An example for the acetylation of starch [40] is shown in Table 1.4. Some samples showed partial formation of a char due to overheating. The data, temperature, and the type of metal chloride showed large effects. Higher temperatures produced greater DS, and FeCl3, AlCl3, SnCl2, and iodine gave the greatest catalytic activities. Table 1.4: Degree of substitution (DS) for acetylation of starch using Lewis acid catalysts. Catalyst

DS at the temperature below  °C

FeCl AlCl SnCl ZnCl SbCl CuCl CoCl NiCl I

.

 °C

 °C

Char . . . . . . . Char

Char . . . . . . . .

 °C . .

 °C

 °C

 °C

. . . . . . . . .

.

.

.

.

1.6 Chemical reagents for pulp and paper Pulping is the process whereby wood fibers are treated to produce pulp; the purpose is to remove lignin without reducing fiber strength. Different pulping processes are used commercially, for example, mechanical, semichemical, and fully chemical methods (kraft and sulfite processes). The pulp is then converted into paper at a paper mill. The finished product may be bleached or nonbleached, depending on the applications and customer requirements [41]. The use of chemical reagents is important to facilitate the processes for both pulp and papermaking [42]. As these processes can be rather complex and may entail by-products that can pollute the environment, the incorporation of green chemistry principles can be very useful, as shown in the examples given below. (a) In the chemical pulping process, foaming is often a major problem and defoamers are needed to reduce foam [43]. Many defoamers contain silicone-containing ingredients, but the silicone compounds are not biodegradable. In the patent literature, soybean oil has been used to reduce the amount of silicone in the defoamers, and the resulting products still show satisfactory defoaming activities [44, 45]. (b) In pulp and paper processes, biocides are needed to control the growth of microorganisms. Different types of biocides are being used for this purpose, and an effective

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type includes haloamines (sometimes also used for swimming pools for microbiological control) [46]. Two novel approaches to generate haloamines, including an electrochemical method [47] and a solid method [48], have been reported as alternatives. (c) Bleaching is needed to reduce color in the pulp. A new method of bleaching involving singlet oxygen has been reported [49]. An enzymatic method that involves the use of laccase together with a mediator is also known [50]. Toward this end, some new laccase mediators have also been disclosed [51–54].

1.7 Conclusions The above examples hopefully demonstrate the utility of green chemistry principles in designing and developing new and improved chemical processes in several different applications. Some of the examples shown are geared toward specific applications, for example, extraction of specific ingredients in food items, reduction of acid use for acylation of polysaccharides, and processing of chemicals for pulp and paper. Others have more general applicability, for example, enzyme catalysis, use of microwave, and reduction of organic solvents. It is noteworthy that in the application of green chemistry principles, a variety of different reactions and processes are involved, and many projects require multidisciplinary teams, working collaboratively to innovate, solve problems, and optimize the processes in order to achieve the project goals. It may be noted that the practice of chemistry applies to a wide range of economic activities, including commodity and specialty chemicals, pharmaceuticals, petrochemicals, plastics/rubber, minerals, biochemical/biotech, and automotive. The development and manufacturing of products in these industrial sectors all require appropriate processes. The adoption of green chemistry principles for these processes can be a great opportunity for sustainability development and for innovation. In view of the current interest in sustainability and green chemistry by the research and industrial communities, further applications of sustainable green chemistry are anticipated in the future.

References [1] [2] [3] [4] [5]

United Nations. https://sdgs.un.org/goals (accessed October 28, 2022). American Chemical Society. https://www.acs.org/content/acs/en/sustainability.html (accessed October 28, 2022). U.S. Environmental Protection Agency. https://www.epa.gov/greenchemistry/basics-greenchemistry# (accessed October 28, 2022). Anastas, P. T.; Warner, J. C. Green Chemistry: Theory and Practice, Oxford Univ. Press, 1998. Green Chemistry Institute. http://www.acs.org/content/acs/en/greenchemistry.html (accessed July 17. 2022).

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[6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21]

[22]

[23] [24] [25] [26] [27] [28] [29] [30] [31]

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Cheng, H. N. Science and Sustainability. Chem. Eng. News, 2021, 99(9), 36, (March 15, 2021). Cheng, H. N. Sustainability Collaboration, and Innovation. Chem. Eng. News, 2020, 98(6), 44, (February 10, 2020). Cheng, H. N.; https://hncheng-acs.org/ (accessed October 28. 2022). Whittall, J.; Sutton, P. W. Applied Biocatalysis: The Chemist’s Enzyme Toolbox, Wiley, 2021. Grunwald, P. (Ed.) Pharmaceutical Biocatalysis, Jenny Stanford Publishing, 2021. Cheng, H. N.; Gross, R. A. (Eds.), Sustainability and Green Polymer Chemistry, Vol. 2. Biocatalysis and Biobased Polymers. in: ACS Symposium Series, Number 1373, American Chemical Society, 2020. Kobayashi, S.; Uyama, H.; Kadokawa, J. (Eds.), Enzymatic Polymerization Towards Green Polymer Chemistry, Springer Nature, 2019. Turner, N. J.; Humphreys, L. Biocatalysis in Organic Synthesis, Royal Society of Chemistry, 2018. Cheng, H. N.; Gross, R. A.; Smith, P. B. (Eds.). Green Polymer Chemistry: Biobased Materials and Biocatalysis. in: ACS Symposium Series, Number 1191, American Chemical Society, 2015. Grunwald, P. (Ed.) Industrial Biocatalysis, CRC Press, 2015. Cheng, H. N.; Gu, Q.-M. Enzyme-Catalyzed Modifications of Polysaccharides and Poly(ethylene Glycol). Polymers 2012, 4, 1311–1330. Loos, K.; Biocatalysis in Polymer Chemistry, Wiley-VCH, 2011. Qiao, L.; Gu, Q.-M.; Cheng, H. N. Enzyme-Catalyzed Synthesis of Hydrophobically Modified Starch. Carbohydr. Polym. 2006, 66, 135–139. Gu, Q.-M.; Michel, A.; Maslanka, W. W.; Staib, R. R.; Cheng, H. N. New Polyamide Structures Based on Methyl Acrylate and Diamine. ACS Polym. Prepr. 2009, 50(2), 54–55. Cheng, H. N.; Gu, Q.-M. Synthesis of Poly(aminoamides) via Enzymatic Means. ACS Symp. Ser. 2010, 1043, 255–263. Biswas, A.; Kim, S.; Gómez, A.; Buttrum, M.; Boddu, V.; Cheng, H. N. Microwave-Assisted Synthesis of Sucrose Polyurethanes and Their Semi-Interpenetrating Polymer Networks with Polycaprolactone and Soybean Oil. Ind. Eng. Chem. Research, 2018, 57, 3227−3234. Biswas, A.; Sharma, B. K.; Willett, J. L.; Vermillion, K.; Erhan, S. Z.; Cheng, H. N. Novel Modified Soybean Oil Containing Hydrazino-ester: Synthesis and Characterization. Green Chem. 2007, 9, 85–89. Biswas, A.; Shogren, R. L.; Willett, J. L.; Erhan, S. Z.; Cheng, H. N. Enzymatic Products from Modified Soybean Oil Containing Hydrazino-ester. ACS Symp. Ser. 2008, 999, 76–85. Biswas, A.; Kim, S.; Selling, G. W.; Cheng, H. N. Microwave-Assisted Synthesis of Alkyl Cellulose in Aqueous Medium. Carbohydr. Polym. 2013, 94, 120–123. Sutivisedsak, N.; Cheng, H. N.; Willett, J. L.; Lesch, W. C.; Biswas, A. Effect of Microwave Extraction on Phenolic Content of Beans. Food Res. Int. 2010, 43, 516–519. Biswas, A.; Sutivisedsak, N.; Cheng, H. N.; Willett, J. L.; Lesch, W. C.; Tangsrud, R. R. Extraction and Analysis of Antioxidant Capacity in Eight Edible Beans. J. Food Agric. Environ. 2012, 10 (1), 89–96. Cheng, H. N.; Gu, Q.-M. Synthesis of Poly(aminoamides) via Enzymatic Means. ACS Symp. Ser. 2010, 1043, 255–263. Gu, Q.-M.; Michel, A.; Maslanka, W. W.; Staib, R. R.; Cheng, H. N. New Polyamide Structures Based on Methyl Acrylate and Diamine. ACS Polym. Prepr. 2009, 50(2), 54–55. Biswas, A.; Cheng, H. N.; Appell, M.; Furtado, R. F.; Bastos, M. S. R.; Alves, C. R. Preparation of Xylan Esters with the Use of Selected Lewis Acids. ACS Symp. Ser. 2020, 1347, 33–42. Stone, D. A.; Biswas, A.; Liu, Z.; Boddu, V.; Cheng, H. N. Synthesis and Characterization of an Ironcontaining Fatty Acid-based Ionomer, Int. J. Polym. Sci. 2019, 3024784. Dai, Y.; Spronsen, J.; Witkamp, G.-J.; Verpoorte, R.; Choi, Y. H. Natural Deep Eutectic Solvents as New Potential Media for Green Technology. Anal. Chim. Acta, 2013, 766, 61–68.

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[32] Dai, Y.; Rozema, E.; Verpoorte, R.; Choi, Y. H. Application of Natural Deep Eutectic Solvents to the Extraction of Anthocyanins from Catharanthus roseus Replacing Conventional Organic Solvents. J. Chromatogr. 2016, 1434, 50–56. [33] Gómez, A. V.; Biswas, A.; Tadini, C. C.; Furtado, R. F.; Alves, C. R.; Cheng, H. N. Use of Natural Deep Eutectic Solvents for Polymerization and Polymer Reactions. J. Braz. Chem. Soc. 2019, 30, 717–726. [34] Gómez, A. V.; Tadini, C. C.; Biswas, A.; Buttrum, M.; Kim, S.; Boddu, V.; Cheng, H. N. Microwaveassisted Extraction of Soluble Sugars from Banana Puree with Natural Deep Eutectic Solvents (NADES). LWT – Food Sci. Technol. 2019, 107, 79–88. [35] Heinze, T.; Liebert, T.; Koschella, A. Esterification of Polysaccharides. Springer, 2006. [36] Biswas, A.; Shogren, R. L.; Willett, J. L. A Solvent-less Method to Prepare Cellulose or Starch Acetate. Biomacromolecules, 2005, 6, 1843–1845. [37] Biswas, A.; Selling, G. S.; Shogren, R. L.; Willett, J. L.; Buchanan, C. M.; Cheng, H. N. Iodine-catalyzed Esterification of Polysaccharides., Chim. Oggi (Chem. Today). 2009, 27(4), 4–6. [38] Cheng, H. N.; Dowd, M. K.; Selling, G. W.; Biswas, A. Synthesis of Cellulose Acetate from Cotton Byproducts. Carbohydr. Polym. 2010, 80, 450–453. [39] Cheng, H. N.; Dowd, M. K.; Shogren, R. L.; Biswas, A. Conversion of Cotton Byproducts to Mixed Cellulose Esters. Carbohydr. Polym. 2011, 86, 1130–1136. [40] Biswas, A.; Kim, S.; Furtado, R. F.; Alves, C. R.; Buttrum, M.; Boddu, V.; Cheng, H. N. Metal Chloridecatalyzed Acetylation of Starch: Synthesis and Characterization. Int. J. Polym. Anal. Charac. 2018, 23, 577–589. [41] Rojas, O. J.; Gonzalez, R. W. Forestry Encyclopedia: Pulp. https://sites.google.com/site/forestryency clopedia/Home/Pulp (accessed 10/28/22). [42] North Carolina State Univ., Opportunities in Papermaking Wet-end Chemistry. https://hubbepaperchem.cnr.ncsu.edu/additives-and-ingredients/ (accessed 10/28/22). [43] Pelton, R.; Flaherty, T. Defoamers: Linking Fundamentals to Formulations. Polym. Int. 2003, 52, 479–485. [44] Cheng, H. N.; Fernandez, E. O.; Sheepy, J. M. Defoamers Emulsion Compositions for Pulp Mill Applications. U.S. Patent 7,893,115, February 22, 2011 [45] Cheng, H. N.; Fernandez, E. O.; Sheepy, J. M. Defoamers for Pulp and Papermaking Applications. U.S. Patent 7,879,917, February 1, 2011. [46] Corbel, G. Pulp & Paper. in: W., Paulus (Eds) Directory of Microbicides for the Protection of Materials. Springer, Dordrecht, 2004. https://doi.org/10.1007/1-4020-2818-0_21 [47] Sharoyan, D. E.; Cheng, H. N.; Mayer, M. J.; Singleton, F. L. Process and Apparatus for Generating Haloamine Biocides. US Patent 8,747,740 B2, June 10, 2014. [48] Cheng, H. N.; Solid Biocidal Compositions and Methods of Using the Same. U.S. Patent Application 2014/0080707 A1, March 20, 2014. [49] Hollomon, M. G.; Cheng, H. N. Selectivity Improvement in Oxygen Delignification and Bleaching of Lignocellulose Pulp Using Singlet Oxygen. US Patent Application 2009/0090478 A1, April 9, 2009; WO 2009048525 A3, May 28, 2009. [50] Virk, A. P.; Sharma, P.; Capalash, N. Use of Laccase in Pulp and Paper Industry. Biotechnol. Prog. 2012, 28, 21–32. [51] Cheng, H. N.; Delagrave, S.; Gu, Q.-M.; Michalopoulos, D. L.; Murphy, D. J. Laccase Activity Enhancers. PCT International, WO 2003/023043 A1, 3/20/03; US Patent Appl. Publ., 20030096394 A1, 5/22/03. [52] Cheng, H. N.; Delagrave, S.; Gu, Q.-M.; Michalopoulos, D. L.; Murphy, D. J. Laccase Activity Enhancers for Pulp Bleaching. PCT International, WO 2003/023134 A1, 3/20/03; US Patent Appl. Publ., 20030089472 A1, 5/15/03.

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[53] Cheng, H. N.; Delagrave, S.; Gu, Q.-M.; Murphy, D. J. Bio-bleaching of Pulp Using Laccase, Mediator, and Chain Transfer Agent. PCT International, WO 2003/023133 A1, 3/20/03; US Patent Appl. Publ., 20030047295 A1, 3/13/03. [54] Cheng, H. N.; Delagrave, S.; Gu, Q.-M.; Murphy, D. J. Enhancing Laccase Activity Using Pro-oxidants and Pro-degradants. PCT International, WO 2003/023142 A1, 3/20/03; US Patent Appl. Publ., 20030094251 A1, 5/22/03.

Ashutosh Negi, Md. Aasif Jawed, Md. Imteyaz Alam✶, M. Ali Haider, S. Fatima, Ejaz Ahmad✶

2 Technoeconomic evaluation and life cycle assessment of biorenewable route to produce high-value aromatics Abstract: Production of aromatic compounds from biomass-derived platform chemicals constitutes an important step in meeting the demand of high-value chemicals from renewable sources. Among all production routes, Diels–Alder cycloaddition has been extensively explored by researchers for one-pot synthesis, high atom efficiency, high selectivity, and low/mild operating conditions. It is noteworthy that technoeconomic analysis (TEA) and life cycle assessment (LCA) provide insights on the economic feasibility and environmental impact of the production pathways. Moreover, TEA and LCA assist in selecting appropriate production routes, ensuring economic viability and environmental sustainability of the production process. This chapter provides an overview on the production of high-value aromatics such as p-xylene, terephthalic acid, toluene, and trimellitic acid (TMLA) from biorenewable feedstocks. Furthermore, case studies on the technoeconomics of p-xylene and TMLA from biorenewable precursors are discussed to identify the key contributing factors and their implications on the production process. Moreover, LCA of p-xylene production from biomass and fossil pathways suggests suitability of second-generation feedstocks.

Acknowledgement: Authors would like to acknowledge the financial assistance from the Department of Science and Technology (Government of India, grant no. DST/TDT/AGRO-52/2019). ✶ Corresponding author: Md. Imteyaz Alam, Department of Chemistry, University of Milan, Via Camilo Golgi, 19 Milan 20133, Italy, e-mail: [email protected] ✶ Corresponding author: Ejaz Ahmad, Department of Chemical Engineering, Indian Institute of Technology (Indian School of Mines) Dhanbad, Dhanbad 826004, Jharkhand, India, e-mail: [email protected] Ashutosh Negi, Renewable Energy and Chemicals Laboratory, Department of Chemical Engineering, Indian Institute of Technology Delhi, New Delhi 110016, India; School of Interdisciplinary Research, Indian Institute of Technology Delhi, New Delhi 110016, India; Centre for Automotive Research and Tribology, Indian Institute of Technology Delhi, New Delhi 110016, India Md. Aasif Jawed, Department of Chemical Engineering, Aligarh Muslim University, Aligarh 202002, Uttar Pradesh, India M. Ali Haider, Renewable Energy and Chemicals Laboratory, Department of Chemical Engineering, Indian Institute of Technology Delhi, New Delhi 110016, India S. Fatima, Centre for Automotive Research and Tribology, Indian Institute of Technology Delhi, New Delhi 110016, India

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2.1 Introduction Aromatic compounds are building blocks of the petrochemical industry that constitutes approximately one-third of the commodity petrochemical market [1]. In this regard, benzene, toluene, and xylenes, collectively referred to as BTX, and a few other vital aromatics such as terephthalic acid (TPA) and trimellitic acid (TMLA) are the key molecules that have been widely used in petrochemical industries to produce a wide range of value-added products. The conventional routes for aromatic production involve dehydrogenation, hydrogenation, isomerization, and hydrocracking of naptha [2–4]. It is noteworthy that these routes are multistep low-atom-efficient reactions, energy intensive, and require expensive catalysts such as noble metals. Moreover, it also increases the carbon load in the atmosphere, owing to its origin from a nonrenewable resource. Furthermore, crude oil prices are volatile, and thus create uncertainty in fixing the sales price for aromatics. Therefore, it necessitates exploring carbonneutral and less-price-sensitive alternative feedstocks to produce aromatics. As a result, biomass-derived routes for aromatic production have gained significant attention due to their abundance and ability to create a carbon-neutral cycle [1, 5]. Accordingly, a wide range of thermal, chemical, and biological processes have been reported to create a green and biobased aromatics economy, out of which catalytic routes have emerged as most promising. In particular, the production of biorenewable aromatics via Diels–Alder (DA) cycloaddition reaction has attracted much interest among researchers due to the possibility of one-pot synthesis, enhanced atom efficiency, and high selectivity [6]. In some cases, DA cycloaddition reactions may not even require the presence of an expensive catalyst to convert reactant into the desired product [7]. Moreover, minimal by-product formation is reported during aromatic production via DA cycloaddition reaction, which makes it suitable for scale-up to a commercial scale. In particular, DA cycloaddition reactions to produce p-xylene, TPA, toluene, and TMLA are of significant interest to the scientific community. It is possibly due to their multiple applications in plastics, paints, resins, adhesives, pharmaceutical, and agricultural industries. Figure 2.1 illustrates the primary difference between carbon neutrality for p-xylene, TPA, toluene, and TMLA production from conventional fossil fuels and biorenewable resources. Additional carbon load in the form of CO2 is added to the environment at the end of life cycle of the aromatics produced from fossil fuels. On the contrary, CO2 emitted after the end of life of aromatics produced from biorenewable resources gets consumed by plants to become feedstock again, thus, creating a closed carbon loop. Figure 2.1 also highlights necessary reaction steps to produce desired aromatics from the biorenewable resources. Firstly, lignocellulosic biomass gets delignified and depolymerized to yield C6 sugars. Isomerization of glucose follows up to yield fructose in the next step which yields 5-hydroxymethylfurfural (HMF) via dehydration reaction. Eventually, HMF produced may react with the dienophiles to yield TMLA via DA reaction due to the double bonds in the furanic ring. Alternatively, HMF may yield 2,5-dimethyl furan (DMF) via reduction reaction, which indeed serves

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15

as a precursor to derive p-xylene and TPA. A representative reaction mechanism for the production of p-xylene, TPA, toluene, and TMLA from biomass substrates is presented in Figure 2.2. p-Xylene production from DMF (a) mainly involves two steps: initially DMF (diene) reacts with ethylene (dienophile) via DA cycloaddition reaction and produces an oxanorbornene intermediate which on dehydration yields p-xylene. Similarly, isoprene (diene) and propenoic acid (dienophile) react via DA cycloaddition and produce an intermediate which after subsequent dehydrogenation and oxidation produces TPA (b). Furthermore, 2-methylfuran (diene) and ethylene (dienophile) via DA cycloaddition get converted to an oxanorbornene intermediate product and subsequent dehydration of it yields toluene (c). In case of TMLA, HMF (diene), and propenoic acid (dienophile) via DA cycloaddition form an oxanorbornene intermediate product, which follows dehydration and oxidation to yield TMLA. Table 2.1 illustrates different applications and market values for the concerned pxylene, TPA, toluene, and TMLA molecules. In this regard, p-xylene is an important aromatic compound that has applications as a precursor to produce several highvalue chemicals including TPA and dimethyl-terephthalate, resin for fibers, films, and beverage containers, as well as plasticizers [8, 9]. The current global market for pxylene is approximately $59 billion as of 2021 [10]. Similarly, TPA is another important building block aromatic molecule for the polymer industry to produce polyethylene terephthalate (PET) bottles, containers, and polymer films [11, 12]. The current market of TPA is approximately $45 billion and growing rapidly due to high demand of PET products worldwide [13]. Likewise, toluene is important for producing benzene, xylene, toluene diisocyanate, and trinitrotoluene. Other key applications of toluene include gasoline additive, and solvent for paints, sealants, and adhesives [14], with a worldwide market of approximately $23 billion [15]. In addition to p-xylene, TPA, and toluene, TMLA is an essential commodity chemical used for paints, coatings, resins, and adhesive applications. As an estimate, the global market of TMLA and its derivative will reach $470 million by 2025 [16]. Thus, this chapter discusses the contemporary state of the art to produce these aromatics from biorenewable resources via DA cycloaddition reaction. The effect of operating conditions, catalyst composition, and other parameters have been reviewed, which follows case studies on technoeconomic analysis (TEA) of p-xylene and TMLA production from biorenewable resources.

2.2 Production of aromatics from biorenewable resources DA cycloaddition reaction using biorenewable DMF as diene and ethylene as dienophile has been explored extensively for the production of p-xylene. In this regard, Rohling et al. [17] have used high- and low-silica alkali-exchanged faujasite catalysts to observe that low-silica faujasite shows better activity toward DA cycloaddition reaction for p-

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Figure 2.1: Fossil fuel (a) and biorenewable route (b) for the production of desired aromatics.

xylene production (Table 2.2, entry 1). The authors hypothesized that the cooperative nonlinear effects in faujasite micropores could be the major reason for their enhanced activity. Similarly, Wijaya et al. measured 60% p-xylene yield (Table 2.2, entry 2) in the presence of silica alumina aerogel catalysts having an equal ratio of Si/Al. The authors observed that the presence of Brønsted acid sites is a limiting factor for p-xylene yield due to their influence on the dehydration of cycloadduct product [24]. Similar observations have been made by Williams et al. [25] who measured 95% DMF conversion and 67.5% p-xylene yield (Table 2.2, entry 3) in the presence of Brønsted acid sites containing H-Y zeolite. Furthermore, Kim et al. [26] demonstrated that the presence of Brønsted acid sites on external surfaces of beta-zeolite further improves p-xylene yield to 79.4% (Table 2.2, entry 4) from DMF. Moreover, it is possible to enhance the p-xylene yield to 90% (Table 2.2, entry 5) in the presence of beta-zeolite by increasing the reaction pressure [27]. Alternatively, the reaction temperature can also be raised till 300 °C to achieve up to 97% p-xylene yield (Table 2.2, entry 6) from biorenewable DMF in the presence of alumina-doped H-beta-zeolite [28]. It is noteworthy that the appropriate Brønsted/Lewis acid ratio reduces the coke formation, thereby enhancing the desired product formation. In contrast, loading phosphoric acid on dealuminated beta-zeolite caused a drastic

17

2 Technoeconomic evaluation and life cycle assessment of biorenewable route

Figure 2.2: Reaction mechanism for the production of p-xylene, TPA, toluene, and TMLA (adapted from [17–20]).

Table 2.1: Fossil-derived p-xylene, terephthalic acid, toluene, and trimellitic acid. Aromatic compound

Applications

p-Xylene

Resins, plasticizers, and precursors for chemicals

 []

[, ]

Terephthalic acid (TPA)

Packaging material, plastic products, and plasticizers

 []

[, ]

Toluene

Precursor for chemicals, and gasoline blending

 []

[]

Trimellitic acid (TMLA)

Adhesives, paints, coatings, resin synthesis, plasticizers, and anticancer drugs

. []

[, ]

✶

Market value References (billion $ in )

2021 basis market values are calculated using compound annual growth rate from the base year of respective report.

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decrease in p-xylene yield (51%, Table 2.2, entry 7) which indicates that Brønsted acidity alone may not be the sole reason for higher activity of zeolites [29]. Indeed, the enhanced p-xylene yield could be attributed to the synergistic effect of zeolite acidity and porous structure. A very less (46%) p-xylene yield (Table 2.2, entry 8) from biorenewable DMF measured by Gao et al. [30] in the presence of hierarchical structured SAPO-34 zeolite catalyst having high surface area, but small Brønsted/Lewis acid ratio is indicative of the trade-off between acidity and structural effect of catalysts for DA cycloaddition reaction. Therefore, hierarchical structured NbOx-based catalyst with well-balanced Brønsted/ Lewis acid sites showed high activity to yield 80% (Table 2.2, entry 9) p-xylene [31]. In another study on interrelationship of SnPO catalyst’s structure–activity for p-xylene production shows that tetrahedrally coordinated Sn(IV) active sites may cause up to 93% pxylene yield (Table 2.2, entry 10) [32]. It is worth mentioning that p-xylene can also be produced from other reaction routes. For example, DMF and acrylic acid in the presence of ionic liquids using Sc(OTf)3 as catalyst can yield up to 57% p-xylene (Table 2.2, entry 11), which can further improve to 80–92% by the addition of H3PO4 as cocatalyst [33]. Similarly, Lyons et al. [34] have proposed p-xylene production directly from ethylene as a feedstock via the formation of hexadiene using the DA reaction to measure up to 93% p-xylene yield (Table 2.2, entry 12) in the presence of Pt/Al2O3 catalyst. Like p-xylene, TPA is another important fossil-derived chemical that can be prepared from a wide range of biorenewable resources in the presence of metal catalysts via oxidation and DA cycloaddition reaction. For example, biomass-derived p-cymene yields up to 51% TPA (Table 2.2, entry 13) on oxidation in the presence of Mn/Fe/O catalyst at 140 °C reaction temperature and 2 MPa pressure in 48 h [12]. Similarly, vanillic acid and syringic acid obtained from lignin also yield up to 58.7% TPA (Table 2.2, entry 14) in the presence of activated carbon-supported MoWBO and PdNiO catalysts [35]. TPA yield can further be improved to 85% (Table 2.2, entry 15) using biomass-derived propiolic acid and isoprene as reactants [36]. In particular, propiolic acid and isoprene undergo DA cycloaddition reaction to yield the intermediate 4-methyl-1,4-cyclohexadiene-1carboxylic acid, which on subsequent oxidation in the presence of Co(OAc)2/Mn(OAc)2 catalyst yields TPA [36]. Alternatively, isoprene and biomass-derived acrylic acid can also undergo cycloaddition reaction in the presence of TiCl4 catalyst and subsequent oxidation in the presence of Co2+/Mn2+ to yield up to 94% TPA (Table 2.2, entry 16) [18]. Furthermore, TPA yield can also be improved to 96% (Table 2.2, entry 17) by using p-xylene as a reactant via low-temperature ozone treatment and UV irradiation [37]. It is further noted that the TPA production from p-xylene proceeds via singlet O(1D)- and hydroxyl radical-mediated selective C–H functionalization [38]. Low-temperature p-xylene conversion is also attempted in the presence of CO2-expended solvents and Co/Mn/Br-catalyzed oxidation to yield up to 97% TPA (Table 2.2, entry 18). Similar TPA yield (up to 97%) is achieved by Ghiaci et al. [39] from p-xylene oxidation in the presence of Na-bentonite catalyst at 190 °C (Table 2.2, entry 19). Overall, it can be observed that several biomassderived feedstocks have potential to serve as a precursor to produce TPA, however, under different operating conditions and catalysts. On the contrary, only a few reports

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19

are available on toluene production from biorenewable resources via DA cycloaddition reaction. In particular, production of toluene via DA cycloaddition of 2-methylfuran and ethylene in the presence of zeolites has been reported by Green et al. [19]. The authors observed that the DA cycloaddition reaction rate does not depend much on the Brønsted acid site concentration. However, dehydration of the DA cycloadduct product depends on the Brønsted acid site concentration, thereby limiting the toluene yield to 45.5% (Table 2.2, entry 20). Recently, Dai et al. [14] have also reported the production of toluene using isoprene and acrolein to measure 91% yield (Table 2.2, entry 21) in a Zn-containing ionic liquid at room temperature. However, toluene production from biorenewable resources via DA cycloaddition reaction is yet to be studied in detail. Like toluene, TMLA production from biorenewable resources has not been explored much. In particular, Hu et al. [40] reported the TMLA production from biorenewable pinacol via DA cycloaddition reaction to measure 90% yield (Table 2.2, entry 22). Recently, Haider and coworkers [23] have also proposed several biorenewable pathways for TMLA production from biomass-derived dienes such as HMF, DMF, HMFA, and FDCA and dienophiles such as acrolein, acrylic acid, propylene, and methyl acrylate via formation of an intermediate oxanorbornene product. Moreover, authors have studied the technoeconomic viability of TMLA production from biorenewable precursors to find it commercially profitable at a selling price of $10/kg. The authors also suggested alternative routes to produce up to 100% TMLA yield from HMF (Table 2.2, entry 23) [20]. Table 2.2: Production of biomass-derived p-xylene, TPA, toluene, and TMLA. S. no.

Raw material

Catalyst/s

Operating parameters

Yield (%)

References

p-Xylene 

,-Dimethylfuran, ethylene

K-exchanged Faujasite (KY, Si/Al = .)

 °C,  MPa

−

[]



,-Dimethylfuran, ethylene

Silica alumina aerogel

 °C, – MPa



[]



,-Dimethylfuran, ethylene

H-Y zeolite

– °C, . MPa

.

[]



,-Dimethylfuran, ethylene

Nanosponge-beta zeolite

 °C,  MPa

.

[]



,-Dimethylfuran, ethylene

H-BEA

 °C, . MPa



[]



,-Dimethylfuran, ethylene

Al-modified H-beta zeolite

 °C,  MPa



[]

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Table 2.2 (continued) S. no.

Raw material

Catalyst/s

Operating parameters

Yield (%)

References



,-Dimethylfuran, ethylene

Phosphoric acid supported on deAl-BEA

 °C, . MPa



[]



,-Dimethylfuran, ethylene

Silicoaluminophosphates (SAPO-)

– °C



[]



,-Dimethylfuran, ethylene

NbO and NbOPO

 °C, . MPa



[]



,-Dimethylfuran, ethylene

Tin phosphate

 °C, . MPa



[]



,-Dimethylfuran, acrylic acid

Metal triflates Sc(OTf)

 °C



[]



Ethylene

Ir, Pt/AlO

 °C, . MPa



[]

Terephthalic acid (TPA) 

p-Cymene

Mn/Fe/O

 °C,  MPa



[]



Vanillic acid, syringic acid

Activated carbon-supported MoWBOx, PdNiOx

 °C,  MPa

.

[]



Propiolic acid, isoprene

Co(OAc)/Mn

 °C



[]



Acrylic acid, isoprene

TiCl, Pd(), Co+/Mn+, O

 °C



[]



p-Xylene

 °C, . MPa



[]



p-Xylene

Co/Mn/Br

 °C,  MPa



[]



p-Xylene

Bentonite DAEP-modifiedCo/Mn nanoparticle

 °C, . MPa



[]

Toluene 

-Methylfuran, ethylene

H-BEA, Sn-BEA

– °C, . MPa

.

[]



Isoprene, acrolein

ZnCl, Pt/AlO

 °C



[]



[]



[]

Trimellitic acid (TMLA) 

Pinacol and diethyl Pd/C, Co/Mn/NHPI maleate



HMF, propenoic acid

RuCu/C

 °C, . MPa

2 Technoeconomic evaluation and life cycle assessment of biorenewable route

21

Numerous reaction pathways have been identified for the production of the aforementioned aromatics. However, to ensure profitable commercial-scale production, technoeconomic feasibility analysis is an important criteria, which should be evaluated in the initial stage. Noteworthy, life cycle assessment (LCA) of the selected route provides insights on the environmental impact during production, utilization, and disposal or recycling. In this regard, understanding of TEA and LCA is essential for synthesizing aromatics from biomass-based precursors. Section 2.3 discusses case studies on the TEA of p-xylene and TMLA production. Moreover, Section 2.4 discusses LCA case study on biomass-derived p-xylene production.

2.3 Technoeconomic analysis Technoeconomics is a tool to evaluate technical feasibility and economic viability of the production systems (Figure 2.3). In case of chemical production processes, technical feasibility relates to optimal sequencing of unit operations to obtain desirable conversion of raw materials and selectivity of products. On the contrary, economic viability measures profitability parameters such as net present value (NPV), payback period (PB), and internal rate of return (IRR) of the process for setting up manufacturing units. Overall, technoeconomic studies are necessary for evaluating different alternatives of plant design and production routes for a product scheme to ensure optimal performance output in terms of technical and economic aspects [20]. In this regard, case studies on the TEA of p-xylene and TMLA production are presented in the subsequent sections.

2.3.1 Technoeconomic analysis of p-xylene Ierapetritou and coworkers [41] have presented a comprehensive study on the technoeconomics of p-xylene production from 600,000 metric tons of biomass-derived starch/ year. Findings by the authors considering NPV as a key descriptor for the economic viability of p-xylene production system from starch are briefly described in this case study. The chemical conversion process of starch to p-xylene starts from depolymerization to glucose followed by isomerization to fructose. It follows fructose dehydration reaction to yield HMF which on subsequent hydrogenation yields 78% DMF and 22% by-products in the presence of CuRu/C catalyst and THF solvent. Eventually, DMF reacts with ethylene via DA cycloaddition reaction to produce 196,345 metric ton/year p-xylene. The authors have calculated the components of operating costs and fixed costs to analyze their impact on economics of the production system. The operating cost included raw materials (81%), utilities (13%), operating labor and maintenance (Op. L&M, 1%), and plant and administrative overheads (5%). It shows that the production of p-xylene largely depends on the raw material costs. Therefore, it is desired to have a low-cost raw material for the

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Figure 2.3: Overview of key parameters for technoeconomic analysis of chemical production.

production of green chemicals. Interestingly, the study has found the share of utilities as the second most important factor in the p-xylene production (Figure 2.4). This may be attributed to the energy required to operate the number of reactors in the production of p-xylene from starch, and a series of distillation column for separating desired products. However, the contribution of Op. L&M cost obtained is negligible compared to the raw material cost. The fixed costs include catalyst capital cost (76%), equipment costs (10%), contingency costs (4%), and other costs (10%) including piping, instrumentation, civil, paints, insulation, electrical, and contract fee (Figure 2.5). The large share of catalyst capital costs indicates the requirement of huge initial investment. Although low-cost new and novel catalyst with higher lifespan may reduce the catalyst capital cost and operating costs,

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Figure 2.4: Operating cost components in p-xylene production.

Figure 2.5: Fixed cost components in p-xylene production.

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which ultimately leads to the requirement of lesser initial investments. It is noteworthy that the simultaneous production of purified by-products with the desired product requires addition of a few separators which may have significant effects on the economics of the production unit. Interestingly, a significant (21%) decrement in the p-xylene cost has been obtained by considering by-product values. Profitability of biobased p-xylene production largely depends on the raw material costs, and consideration of commercial value of by-products. In this regard, the source of biomass such as second generation compared to first generation has potential to reduce the final product prices to a significant extent. Further, considering some of the by-products shows 21% reduction in the p-xylene price. This suggests that by achieving better integration of processes (as done in the conventional refineries), the by-products could accrue higher revenues which will ultimately reduce the per unit cost of biobased p-xylene production.

2.3.2 Technoeconomic analysis of TMLA Haider and coworkers [42] have studied the production of TMLA from biomassderived dienes (HMF, DMF, HMFA, FDCA, FDCA ester) and dienophiles (propylene, acrolein, methyl acrylate, and acrylic acid) via DA cycloaddition reaction, utilizing density functional theory simulations. DA cycloaddition reaction led to the formation of an intermediate oxanorbornene product, which after dehydration and oxidation yields TMLA. Noticeably, for ease of oxanorbornene formation, electron-deficient dienophiles such as acrylic acid with HMF (diene) form a suitable reactant combination. In solvent-free conditions, normal and inverse frontier molecular orbital (FMO) gaps for acrylic acid and HMF are 3.19 eV and 3.77 eV, respectively, with an activation energy of 48.1 kJ/mol. On the contrary, normal and inverse FMO gaps for acrylic acid and DMF are 2.22 eV and 6.13 eV, respectively, with an activation energy of 47.0 kJ/mol. Both routes suggest promising pathways for TMLA production. Further, the same research group has studied technoeconomic viability of TMLA production from biorenewable HMF. A 5 kmol/h HMF feed rate (6,093 tons/year) is considered for the analysis in twostep and one-step reactor process. Advance System for Process Engineering (ASPEN plus) has been employed to model process flow sheet and analyzing technical feasibility of TMLA production system. Furthermore, the economic viability of routes has been examined via ASPEN economic analyzer (base country: USA). Nonrandom twoliquid Redlich-Kwong (NRTL-RK) activity coefficient model is utilized to calculate liquid–liquid and liquid–vapor interactions in the process. It is noteworthy that the stoichiometric reactor has been employed for the analysis of both reactor setups. The proposed reaction pathways for TMLA production from HMF via two-step and onestep reactor setup are illustrated in Figure 2.6. In the first pathway (a), HMF is converted to DMF via hydrodeoxygenation (493 K, 8 bar) and produces DMF (diene) with

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50% selectivity, which after separation reacts with propenoic acid (dienophile) via DA cycloaddition reaction (573 K, 58 bar) to produce oxanorbornene intermediate-1. Dehydration and oxidation of oxanorbornene intermediate −1 yield 99% pure TMLA. Moreover, in the second pathway (b), HMF (diene) reacts with propenoic acid (dienophile) to form oxanorbornene intermediate-2, which after dehydration and oxidation produces 100% pure TMLA.

Figure 2.6: TMLA production from HMF via two-step and one-step reactor setup.

This is important to mention that the raw material cost accounts a major share (~80%) of total operating costs in the proposed pathways. Among the raw materials, heptane (solvent) costs were found to be the key influencing parameter for economic viability of the TMLA production system. Noticeably, in the two-step reactor process, TMLA production without recycle of the solvent was found to be economically unviable with a negative NPV of –$424 million. On the contrary, 95% recycle of solvent (considering 5% make-up in each cycle) in the process presents an economically viable alternative for TMLA production. With 95% solvent recycling in the two-step reactor setup, the financial parameters are calculated as $43 million NPV, 39.42% IRR, and 5.59-year PB. Moreover, in a single step-reactor system, the economic parameters improved to $182 million NPV, 105.94% IRR, and 2.44-year PB. The enhanced profitability in one-step reactor setup process could be attributed to high HMF selectivity and no by-product formation. Noticeably, both pathways consider $10/kg sale price of TMLA. Furthermore, the authors have presented a futuristic scenario, considering a decrease in HMF price to 10–40%, due to upgradation in biomass conversion technologies. This would have a positive effect on the profitability of TMLA production from biobased HMF. The authors reported that each 10% drop in HMF cost will enhance the IRR of ~ 4%. This indicates that the commercial-scale viability of TMLA production would enhance significantly in future by advancement in state-of-the-art biomass conversion technologies.

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In another scenario, the impact of an increase in TMLA sale price from $10/kg to $40/kg has been analyzed. It is noteworthy that the TMLA production was found to be economically viable at $10/kg sale price. However, with an increase in sale price to $40/kg, the IRR increased to 484.8% and PB reduced to 1.27 years. TMLA production from biomass substrates is economically viable if the solvent recycling is employed. TMLA production at $10/kg sale price is economically viable irrespective of the selected pathways (two-step and one-step). Furthermore, the reduction in raw material costs due to advancement in biomass conversion technologies has the potential to improve the profitability of TMLA production significantly. This indicates that biobased resources could provide sustainable alternatives for TMLA production in an economically viable manner.

2.4 Life cycle assessment LCA is a technique for the investigation of environmental impact of a product/service throughout its life. The LCA includes all stages of a product, from raw material generation to utilization, and finally recycling or waste disposal [43]. The key features of LCA include (a) a systematic environmental assessment according to the stated goals and scope; (b) provisions to ensure confidentiality and proprietorship matters; (c) a functional unit for relative analysis; (d) a methodological framework for upgradation in the state-of-the-art technologies; and (e) cradle-to-grave or gate-to-gate assessment options. The environmental impact assessment of biobased chemical production pathways on decarbonization of chemical market is essential to identify suitable utilization routes. With rising CO2 concentration in the atmosphere, the selection of appropriate raw materials should also be weighed upon their environmental emissions during production/cultivation, processing, application, disposal, and recycling. A case study of p-xylene production is discussed to provide a brief overview of LCA.

2.4.1 Life cycle analysis of p-xylene LCA of biomass-derived p-xylene production from first-generation (starch from maize) and second-generation (red oak) biomass compared to conventional fossil-derived route has been reported by Ierapetritou and coworkers [8]. The system boundary considers the generation of raw materials, processing, and p-xylene production. It is important to mention that this study does not consider further utilization of p-xylene in value-added applications such as manufacturing of PET. This indicates that the scope includes only the production of p-xylene from first- and second-generation biomass (gate to gate). It is noteworthy that the functional unit (quantitative measure of an LCA study) of this study selected 1 metric ton for p-xylene production.

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As illustrated in Figure 2.7, the goal of this study is to examine the environmental performance of biobased p-xylene production. Ecoinvent v2.2 database is utilized for inventory analysis, and cultivation of maize and red oak data is directly collected from the repository. Furthermore, the dataset for processing of maize is taken from Ecoinvent; however, the inventory data for processing of red oak to glucose is collected from ASPEN plus due to unavailability in the Ecoinvent database. It is important to mention that materials utilized for other than manufacturing are excluded from the LCA, and biomass feed is considered to be collected from 100 km radius from the plant. Water is utilized for cooling and steam is used for heating applications in the process. The inventory data is collected for 18 impact categories, namely, climate change, ozone depletion, human toxicity, photochemical oxidant formation, particulate matter formation, ionizing radiation, terrestrial acidification, freshwater eutrophication, marine eutrophication, terrestrial ecotoxicity, freshwater ecotoxicity, marine ecotoxicity, agricultural land occupation, urban land occupation, natural land transformation, water depletion, metal depletion, and fossil depletion. Noticeably, the authors have used SimaPro v7.3.3 platform for the environmental impact assessment. Further, ReCepi v1.0 tool is employed for the assessment of the databases considering with and without mass and economic allocations in the selected scenarios. The oak-based p-xylene production results showed relatively lesser environmental impacts compared to starch-based production. It is noteworthy that cultivation and processing of maize starch appeared the key contributors in poor environmental performance in the majority of impact categories. Moreover, utilization of heating steam during p-xylene production from maize starch is found to be another important contributor for higher environmental impact. Furthermore, interpretation of data is done through sensitivity and Monte Carlo uncertainty analysis. The sensitivity analysis results indicate that higher selectivity of p-xylene production could contribute to better environmental performance. Moreover, the use of biobased reactants may assist in reducing the environmental impact significantly. The starch-based (first-generation biomass) p-xylene production is more environmentally harmful compared to fossil-derived p-xylene due to its negative environmental externalities during biomass cultivation and processing. The processing stage utilizes solvents, acids, and energy which ultimately led to higher environmental impacts. Interestingly, the oak-based (second-generation biomass) p-xylene production shows promising results in LCA compared to fossil-derived route. It is noteworthy that the state-of-the-art integrated biorefineries must focus on aspects such as new catalyst development, process design and optimization, supply chain management, and utilization of biobased reactants to compete with conventional refineries in terms of economics and environmental impacts.

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Figure 2.7: Life cycle assessment of p-xylene.

2.5 Summary Production of aromatics from biorenewable pathways has a potential to fulfill the growing global demand in a sustainable manner. Indeed, the DA cycloaddition reaction could play a prominent role in commercial-scale aromatic production from biorenewable resources due to high atom efficiency, high selectivity, and low/mild operating conditions. However, often more than one production routes are possible from the same feedstocks. In this regard, TEA and LCA hold the key criteria for the selection of most appropriate production route. Technoeconomic studies suggest that raw material prices are the key contributors in the total operating cost; therefore, the abundantly available low-cost second-generation biomass such as agricultural residues can be suitable feedstock for the production of green aromatics. Furthermore, LCA also favors the production of aromatics from second-generation biomasses, due to lower environmental externalities associated with them.

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Awais Ahmad✶, Rafael Luque

3 Green chemistry and catalysis Abstract: The ultimate aim of green chemistry includes catalysis, processes, and design of all chemical goods that disregard the use of generation of noxious substances. Application and design of novel catalytic systems and catalysts are concurrently accomplishing the twofold goals of economic benefit and eco-friendly fortification. Green chemistry is an overarching approach, is intricate in the enterprise of chemical processes and products that eradicate the use of perilous materials, and is applicable to all features of chemistry. This tactic actively seeks ways and processes to synthesize products and materials that are auspicious for environment and human vigor. Recent accent on green chemistry imitates a swing away from eminent approach “command-and-control” to environmental problems that clean up through regulation and avert pollution at its source and it also mandated waste treatment and control. This approach seeks new skills and methods which are economically inexpensive and cleaner as waste peers and dumping are inevitable. Green chemistry validates the beauty and power of chemistry; it also utilizes pollution prevention through cautious design and humans can relish the goods on which they depend. In the advancement of green chemistry economic benefits are central drivers. As it rallies the corporate bottom line so every industry is adopting green chemistry day by day and its uses can decrease a wide assortment of operating outlays as well. Waste cohort loses the environmental compliance down and disposal technique becomes needless when waste is reduced or abolished. A fewer processing steps and less solvent usage can lessen the energy and material costs, so material proficiency is also increased.

3.1 Introduction Human health, economic, and environmental compensations realized through this tactic are plateful as a strong enticement to industry to implement green technologies. Adopting the practices of green chemistry has now become a big encounter for industries and other societies and may be viewed via outline of “Twelve principals of Green chemistry” [1]. The ethics of this framework identify that the catalysis is one of the most significant utensils for adoption green chemistry. The catalysis can offer frequent paybacks of green chemistry, including catalytic against stoichiometric amounts of materials, lower energy requirement, less usage of separation agents and processing, and increased ✶

Corresponding author: Awais Ahmad, Departamento de Quimica Organica, Universidad de Cordoba, EdificioMarie Curie (C-3), Ctra Nnal IV-A, Km 396, E 14014, Cordoba, Spain Rafael Luque, Departamento de Quimica Organica, Universidad de Cordoba, EdificioMarie Curie (C-3), Ctra Nnal IV-A, Km 396, E 14014, Cordoba, Spain, e-mail: [email protected] https://doi.org/10.1515/9783110745658-003

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selectivity, and allows lessen usage of hazardous materials. Goals of green chemistry are addressed by “Heterogeneous catalysis” as it provides ease of separation of catalyst and product and it also reduces the need for separation through extraction and distillation. Environmentally being’s catalysts for example zeolites and clays, substitute the toxic catalyst which are in formerly in usage. This chapter climaxes an array of methods in which catalysis will be used as litter thwarting tool of green chemistry. Focusing on catalysts design and its application, the aids to environment, human health and economic goalmouths comprehended via usage of catalysis in processing and manufacturing are also exemplified.

3.1.1 Principles of green chemistry 1. 2.

To preclude waste, design chemical syntheses which leave zero waste to clean up. Scheme such type of fusions which end product consists of the maximum fraction of the starting material as well as zero atoms or waste. 3. Design synthesis with zero or inconsequential toxicity toward the humans as well as environment. 4. Plan such type of chemical products which are copiously operative and nevertheless have petite or no noxiousness. 5. Always evade to such type of solvents, separation agents as well as some other supplementary chemicals. If there use is obligatory then always prefer safer one. 6. Always start the reaction at the room temperature and pressure at any time conceivable. 7. Always prefer feedstock which has renewable properties rather than depletable. Agricultural products, waste of other processes, and some depletable feedstock, i.e., petroleum, natural gas as well as coal, are the some examples of the renewable feed stock. 8. If conceivable then elude the use of blocking as well as protecting groups and temporary variation. Offshoots cause to engender the waste by the use of additional reagents. 9. Catalytic reaction produces less waste as well as they are effective in small proportions, and they can also carry out single reaction frequently. They are desirable toward the stoichiometric reagents, and they use many times to lead the reaction once. 10. To break down the toxic substances design such type of the chemical products which do not mount up in the environment. 11. To abate or eradicate the materialization of the byproduct, real-time monitoring as well as control in the process acquires importance. 12. To curtail the potential toward the chemical calamities such as detonations, fires as well as proclamations to the environment, design chemicals which have their physical forms.

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Figure 3.1: Green chemistry: a promising pillar toward sustainable development.

3.1.2 Catalyst design A catalyst’s design endeavors to enhance features such as gross revenue number, stability, solubility, and laidback to separate from the merchandise. Metal selection and variations in ligands enterprise can provide noteworthy enhancement in energy ingesting, selectivity, and also in solvent consumption. Sometimes catalyst’s better design authorizes the usage of naturally friendly feedstock and components. Bestowing to this we can easily find out that the benefits of green chemistry base on appropriately designing catalysts. Synthesis of a noteworthy class of polycarbonates that are used as binding agents in ceramics can facilitate the development of upgraded catalyst. Copolymerization of cyclohexene oxide and carbon dioxide has been skilled by using an assortment of Zn catalyst. Recently, Coates and coworkers [2] modified catalysts which afford polycarbonate products at milder conditions and enhanced rate versus previous catalysts. Stability of catalysts increased as substitution of bulky N2 ligands for O2 ligands tethered to Zn; thus, the stability and proficiency of catalysts increased. Moreover, a methoxide group of acetate group bound to Zn enables the monomer to link in an irregular sequence and also ensures the polymer chains are almost of the same length. There is also a prodigious benefit of green chemistry in the use of CO2 which is a renewable feedstock and it acts as solvent in the reaction as well as monomer. Furthermore, the strains of energy decrease and reaction rate increases when development of a robust catalyst for polymerization occurs in green chemistry. At Carnegie Mellon University, Terry Collins and team [3] recognized a number of catalysts which in every application activate the

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natural oxidant hydrogen peroxide. These Tetra Amino-Macrocyclic Ligands (TAMLTM) activators also carry elements which are devoid of toxic functional group and are also found in life processes. Collins group found in the designing of these activators; they control the lifetime of the catalyst by varying identify of R group. Catalyst is further vigorous with cyclopropyl group versus methyl group. In the paper and pulp industry, combining hydrogen peroxide and Tetra Amino-Macrocyclic Ligands can treat kraft pulp and also perform delignification process at low temperature. That scheme also reduces the use of chlorine hypochlorite oxidation which engenders chlorinated organics such as tetra chlorodibenzodioxin as an unwanted byproduct. Another application of Tetra Amino-Macrocyclic Ligand activators is found in the laundry sector, where these catalysts can accomplish activation of peroxide and they are also present in household bleaches. The Tetra Amino-Macrocyclic Ligands activator can efficiently inhibit the dye transfer which advance the probable for washing machines hence lessen the water usage and also effective at low temperature. In the field of laundry, the dye hang-up and stain removal property of these catalysis enable both energy and water conservation. In catalyzing peroxide reaction, the versatility of Tetra Amino-Macrocyclic Ligands aptitudes application potentially in the segment of water disinfection. A thoughtful catalyst design in green chemistry enables a waste-free progression and a Cl-free oxidation reaction by means of a non-toxic heavy metal in slight reaction conditions. In numerous chemical processes the advancement in the field of genetic engineering allows the customization of organisms to catalyze significant transformation that are presently verdict application. Frost and Draths [4, 5] demonstrated the usage of bio-catalysts in the synthesis of organic compound. The conversion of d-glucose to cis, cis-muconic acid then abridged to adipic acid in non-virulent strain of E. coli while using genetically engineered Klebsiella pneumoniae. Adipic acid is also a monomer in the manufacturing of nylon-6,6. Production of greenhouse gases and nitrous oxide as a spinoff in traditional synthesis of adipic acid. Additionally, the usage of benzene which is also a renewable carcinogenic compound, at high temperature and pressure. Bio-catalytic technique features all renewable byproducts, uses slight reaction condition, and releases no greenhouse gas and nitrous oxide. Similarly, the usage of E. coli in the genetic engineering field results in an operative catalyst in the manufacturing of catechol which is involved as a chemical building block in the amalgamation of flavors, i.e., vanillin. Thomas [6] reported two new techniques for adipic acid. In one technique, selective air oxidization of terminal methyl group of n-hexane to carboxylic acid occurs using alumino-phosphate molecular-sieve-catalyst with Co ions. N-hexane is slanted toward molecular sieve in such a way that tops of the chains are in close proximity to the radical-generated Co ions; this free radical mechanism has also been anticipated. Molecular sieve catalyst’s oxidation containing iron (III) occurs in the second route of Thomas. This heterogeneous catalyst permits straight oxidation of cyclohexene to adipic acid and also performs leave-taking and salvaging of the catalyst and

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avoids the usage of high toxic and perilous reagents. Thomas’s mutually these routs eradicate the usage of HNO3 which were found in conservative technique of adipic acid synthesis, as well as no creation of greenhouse gas and nitrous-oxide as spinoff. Fish et al. demonstrated the oxidation of alkenes and alkanes by means of t-butyl hydroperoxide and oxygen as oxidant [7, 8]. They also used FBC (fluorous biphasic catalysis). A difficult separation of catalyst and product get by the oxidation of alkanes with t-butyl hydroperoxide occurs in homogenous phase. By exploitation of fluorous biphasic catalysis the oxidation of catalyst and other products residing in separate phase facilitates the recovery and separation. This reaction’s progress depends upon the in situ synthesis of metal complex and precatalyst of a fluor ponytailed ligand. Solid acid catalyst proves more environmentally benevolent alternative toward the conventional process in the nitration of the aromatic composites and they employing mixture of nitric as well as sulfuric acids. Choudary et al. [9] performed an experiment on the frequent zeolite and clay in the nitration of benzene and monosubstituted benzene rings. Results indicate that Fe3 + montmorillonite is the furthermost vigorous catalyst but premier paraselectivity was accomplished through 60% nitric acid and high shape selectivity indicated through the zeolite beta-1 (i.e., catalyst). In the zeolite beta catalyst, improved discrimination and reactivity were perceived as silicon and aluminum ratio and it was declined. Azeotropic amputation of water designed in course of the rejoinder rejuvenated the dynamic acid positions of catalyst, authorizing salvage of the solid acid catalyst. Solid acid catalysis compromises extraordinary cosmos time revenues when associated with the typical mixed acid nitration of aromatics. And from the reaction, paraselectivity and simple separation of the catalyst developed. To transfigure ketones to lactones through Baeyer-villiger reaction, two diverse catalytic etiquettes have been followed. Gupta et al. [10] used atmospheric carbon dioxide as the oxidizing agent to transmute the cyclohexanone to ε-caprolactone and it is contrived through baker’s yeast. Baker’s yeast is also used in place of the m-chloroperoxybenzoic acid and it is very important for shock profound, quick-tempered as well as frequently castoff for test site gauge Baeyer-villiger oxidations. Furthermore, in Baeyer-villiger reaction m-chloroperoxybenzoic demonstrate deprived atom economy. So, an oxygen atom is amalgamated into the product and leave-taking m-chlorobenzoic acid as derivative. Designer yeast produces the anticipated lactone in extraordinary yield and pureness, empowers the reaction to run in an aqueous medium, and yields water as individual derivative. Second discrepancy on the Baeyer-villiger reaction practices air oxidation in the aggregation with molecular sifter catalyst and scratched oxidant [11]. To conform the lactones, metal ion exchanged aluminophosphate catalyst are operative in renovating a sequences of ketones. Cobalt (III) and manganese (III) ions lining the microporous catalyst provide the dynamic positions where the sacrificial oxidant is transformed thru oxygen to peroxy acid. Outside the catalyst, peroxy acid consequently transmuted the ketone to the lactone. Waste acid generated via this method as well as redox molecular filter catalyst eliminates the use of challenging oxidants (i.e CrO3,

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KMnO4). These are frequently used in the stoichiometric. Reactions continue at the low temperature as well as selectively yield the lactone product. Thus it depresses the energy costs as well as curtails the waste generation. Cresol methylation generates as a result methyl anisoles, which are used in the manufacture of dyes as well as agrochemicals. Cresols are blended in tetrahydrofuran with the combination of a methylating agent, including such dimethyl sulphate as well as alkali or a methyl halide and sodium hydroxide, resulting to produce methyl anisoles. Most of chemicals are caustic and noxious, and the aforementioned practice is grossly incompetent of salt. The subsequent invention of a cesium-loaded silica (Cs/SiO2) catalyst stimulates significant specific surface area and conversions in vapor phase methylation of cresols [12]. Undeviating methylation of cresols with methanol promotes atom frugality, as result processed water like merely derivative, but also eradicates salt waste production. Additionally, secure bed vapor level of methylation above a solid catalyst involves uninterrupted dispensation instead than of bunch handling, which seems to be currently employed. Way to manage is preferable in this reaction since that allows for easy dissociation of catalyst and product, regeneration of catalyst, simpler product work-up, and operator steadiness. Paciello et al. [13] detailed the molecular modelling adopted by way of a technique for generating catalytic agent with increased fussiness in olefin hydroformylation. Chelating ligands like bisphosphanes and bisphosphites have been mainly encountered in rhodium catalysts used in the hydroformylation progression. In the transformation of 1-octene to n-nonanal, a calixarene bisphosphite ligand was revealed to have extraordinary regioselectivity (99.5%). Molecular modelling simulations on the catalyst indicate the improvement of the reaction rate without affecting regioselectivity that might be accomplished by reducing the steric requirements of the ligand. Subsequent studies supported this assumption; strong regioselectivity was maintained despite halving the reaction proceeding duration including using gentler reaction conditions. This reaction is dominant green chemistry benefits which include better choosiness and diminished energy needs in advantage of the low temperature and pressure necessities. Bandgar and Kasture [14, 15], invented a system to eliminate carbonyl protecting compounds catalytically underneath microwave radiation as well as solvent-free circumstances. Heavy metals such as mercury (II) chloride but also selenium dioxide are predominantly based on thioacetal and thioketal fragmentation and elimination. Depending on environmental issues involved with mercury usage, less hazardous options to mercury salts are preferred. Warm through the thioacetal or thioketal with a catalytic proportion of kaolinitic clay generates a high yield of the carbonyl chemical. A parallel method for deprotecting 1,1-diacetates has already been developed. In the exclusion of solvent, microwave stimulation of the diacetate also with solid-supported reagent envirocat EPZG (Contract Chemicals Ltd.) generates the aldehyde in higher production. Although it is preferable to avoid prevention stages in green chemistry, once they are inevitable, either of these approaches improved on

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current deprotection procedures. Catalysis abolishes the necessity for organic diluters, including the use of hazardous and destructive chemicals

3.1.3 Catalyst application Catalysts show an imperative starring role in the disciplines of pharmaceuticals, polymers as well as in the petroleum processing and their application is permeating these disciplines. In industries, approximately about 90% processes work under catalysis [16]. Widespread deployment of industrial catalytic processes echoes economic and environmental reimbursements via catalysis. Among over-the-counter pain relievers, ibuprofen is commonly used, and their synthesis needs six steps. In their synthesis, larger portion of the solvent, stoichiometric quantities as well as scarring reagents are used. In their starting process, only 40% of the atoms are amalgamated with the manufactured article, so this protocol demonstrates poor atom economy. On the other hand, manufacturing of benzene hexachloride ibuprofen is consummated in three phases [17]. Reagents are used in the catalytic amounts, but their concentration is greater than 99% of the hydrogen fluoride catalyst which are reprocessed and salvaged. Economy of the atoms gets doubled to 80% and it eventually condenses the amount of the waste engendered. So, it is an important apprehension that this value-added amalgamation of the ibuprofen depends on the anhydrous hydrogen fluoride. Conversely, it serves as both a catalyst and a solvent and works for minimization of the carbon-based and aqueous remaining and in the same way it also enhances the proficiency of the reaction. Naproxen is also used as an anti-inflammatory drug, and it can be amalgamated in elevation yield through the catalytic way [18]. In their synthesis, the final step is the chiral transition metal catalyst and it involves the C₄₄H₃₂P₂ [2, 2-bis (diarylphospheno)-1,1-binaphthyl] in the direction of produce the preferred enantiomer in the 97% yield. To hamper the revolution, high discrimination of the transition metal catalyst is endorsed to steric dynamics. Exercising judgment of the catalysis is very important for underrates and eradicates the prerequisite for the product separation and plummet the use of the solvents as well as separation proxies. Reagents which frequently practice in the oxidation reactions e.g chromium also known as carcinogenic, catalyst be responsible for innocuous replacements for their. To develop the synthesis process of bisnoraldehyde, Pharmacia and Upjhon [19] play an important starring role. Key deriver is used to intermediate the reaction of the progesterone and corticosteroids and they shift from substantial metal oxidant to peroxide, promoter as well as cofactor system. In the revised manufacturing process, it provides the services for natively amended bacterium and whole soya sterols; renewable feedstock is used for this purpose. And these are more competent as well as they enhance the utilization of the feed stock from 15 to 100%. Fabrication of aqueous discarded

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reduces up to 79% via advanced catalytic procedures as well as 89% reduction comes about in non-recoverable carbon-based solvent surplus. Customary catalyst may be accompanied by means of enzymes which are responsible for astonishing discrimination in organic fusion. A correspondent of the castanospermine having the potential toward the AIDS drug and it is amalgamated with the use of the enzyme reagent subtilisin [20]. The regioselectivity of the catalytic agent allows acylation absolutely at the C-1 hydroxyl group and parting the enduring three secondary hydroxyl groups unscathed. Esters of castanospermine necessitate fortification and expatriation of the adjoining hydroxyl groups in the period of their individual synthesis. Rather than enzymatic synthesis of the castanospermine byproducts allows the unpretentious segregation and sanitization of the manufactured goods. And they also recuperate and reclaim the unreacted preliminary substantial as well as eradication of the protection and deprotection strides. Wong and co-workers [21] widely practiced the chemo enzymatic techniques to manufacture an assortment of the biologically imperative composites. Cyclic imine sugars work as the inhibitors of the glycoprocessing enzymes, and it is the one of the best example of the chemo enzymatic methods. Enzymatic aldol condensation revenue (i.e., assortment of azido sugars) is successively hydrogenated underneath the catalytic circumstances to cyclic imine sugars. The amino-carbonyl sugar intermediary was ensnared as its hydrochloride salt to preclude the terminated lessening of the azido sugar, acquiescent of anticipated cyclic imine somewhat the hydrogenated iminocyclitol. In the amalgamation of the nitrogen heterocycles and iminocyclitols, cyclic imines oblige as key role in it. In restructuring the production of the anticonvulsant drug candidate, Eli Lilly and company used an interdisciplinary methodology [22]. In a basic step, to selectively condense the preliminary ketone to optically pure alcohol, a biocatalyst was engaged. To effect the conversion, yeast was preferred and with increasing organic concentration Z. rouxii was deactivated, requiring the design of a three-phase system to preclude the buildup of the product. In a consequent step, additional environmental benefits were comprehended via interchanging chromium oxidation to air oxidation. The net production of the pharmaceutical product was enhanced by threefold with the help of advancement in the processes as well as significant decrease in the bulk of solvent used and magnitudes of the waste produced. For the synthesis of the 100 kg product, 34,000 solvent and 300 kg chromium waste were eradicated. Catalysis process is one of the important findings of new applicable approaches in alternative modification of reaction media. For illustration, the mechanism of an autocatalytic approach has been indorsed for the transformation of benzoic acid esters keen to form benzoic acid in the presence of critical absolute water [23]. Nearcritical water (250–300 °C) displays the high magnitude of ionization constant orders as compared to ambient water by considering a hydroxide as source along with hydronium ions. However, the catalysis of conventional acid or base, the hydroxide as well as hydronium ions do not need to neutralize as a result of eradicating the

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formation of salt byproducts. Moreover, under ambient conditions solvent easily separates out the products. In an aqueous environment, many types of reactions can take place by using specific catalysts in medium. Basically, water in process proved a stable choice of solvent because it is cheap as well as readily accessible, non-toxic in nature, and inflammable. Paquette et al. [24] have performed successfully in his work, especially on an indium catalyst in regard to a variety of carbon–carbon bond in proceeding reactions that were directed in aqueous environment. Allylation of 1,3-dicarbonyl combinations is an illustration that is efficiently endorsed in aqueous solution by using an indium catalyst. Usually processes like cyclization as well as ring expansion and isomerization reaction leading to metal-mediated responses in water have been used. In addition, another ecologically benign solvent, that is supercritical carbon dioxide (SC-CO2), has proved as a worthwhile substitute among the traditional ongoing organic solvents. Moreover, Rayner and coworkers in recent times inspected the catalysis reaction between n-butyl acrylate and as well cyclopentadiene of the Diels–Alder reaction in the substitute of SC-CO2 [25]. In advancement of reaction Scandium tris (trifluoromethanesulfonate) was still more carefully chosen as a catalyst of the Lewis acid, mainly as a consequence of its specific solubility as in SC-CO2. However, selection toward endo or exo was increased up to 24:1 by changing the pressure of the solvent which is a stratifying progress over the attaining selectivity procedure which accomplished in term of solvents (11:1). Under the SC-CO2 conditions, the rate increased was also observed. In this approach, the green manner chemistry lead to benediction having less harmful solvent following the less energy consumption, provide easiness of segregation, as well as the selectivity regarding waste reduction are manifested. Ensuing the contemporary organic solvents along with ionic liquids are also achieving approval as a substitutes. Ionic solvents or liquids are stable as well as non-combustible that are eradicating the threat or risk connected with mostly volatile organic compounds (VOCs). Furthermore, detailed characteristics of ionic form solvent might have changed by modifying the cationic as well anionic identities by enabling the solvent-liquids to be tuned to such a given purpose especially. Kitazume and Zulfiqar [26] described in their research report about the Aza–Diels–Alder conducting a reaction including ionic liquids. The Aza-Diels-Alder reaction is mainly executed in terms of organic solvent involving the advancement of corrosive Lewis acid catalyst reactions. This innovative approach contributed a microencapsulated regarding Lewis acid catalyst, i.e., scandium trifluoromethanesulfonate, which itself is recoverable as well as reusable. During purification, the ionic liquid is, however, reused. This synthesis reveals whether ionic liquids could be used as alternate solvents in conventional organic reactions. Catalysts are crucial for the production of biopolymers. As an example, the Donlar Corporation adopted a catalytic reactive mechanism to modulate polymerize thermal polyaspartic acid (TPA) [27]. The catalytic reaction leads to lower temperature range and enhanced physical as well as performance aspects of the polymer. TPA, is however, a non-toxic abled-bodied biodegradable polymer which indeed is considered

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as a feasible substitute idiomatic to non-biodegradable polyacrylic acid (PAC) as well. TPA was shown to be functional in agricultural applications via improving fertilizers and mineral absorption of plants. TPA proved to be beneficial in the water treatment industry as a struvite inhibitor. Organic polyhydroxyalkanoates (PHAs) are still biodegradable embodiment polymers. These natural attained polyesters driven straight from recombinant different plants either from renewable energy sources using microbial fermentation in aqueous conditions. Gross and colleagues devised PHAs featuring superior physio-mechanical attributes with including mainly poly (ethylene glycol) (PEG) involving the broth culture [28]. Additionally, PEGs are mostly shown to be efficacious in modulating the molecular weight as well as structure of PHAs. In conjunction to the product’s biodegradability, such technique provides significant environmental benefits by exploiting renewable fuel sources inhabiting fructose and water more even in the reaction medium.

3.2 Conclusions This chapter focused on catalysis application in line with green chemistry aspirations for a more sustainable future. Catalysis plays a promising role toward the goals of green chemistry like water or SC-CO2 which are used as alternative solvents, by utilization of biobased renewable feedstock such as energy minimization as well as glucose. However, prospect and catalytical potential surpass their results. Further recent trends in catalysis clinch scientist to work on it for green chemistry. Catalysts that stimulate potentially innocuous starting materials while also boosting reaction speeds will minimize the existing reliance on volatile as well as harmful chemicals. With this heterogeneous catalysis also help toward green energy production to meet the global energy crises such as production of hydrogen energy, thermal energy production as well as producing new innovations in energy storage devices. Green chemistry approach using catalysis boosts the level of science with its modern ideas such as organic conversion into useful products. Green chemistry with catalysis is cost-effective, productive as well as ecofriendly for tackling recent trends in science and environmental issues

References [1] [2] [3]

Anastas, P. T.; Warner, J. C. Green Chemistry: Theory and Practice, Oxford University Press, New York, 1998, p. 30. Cheng, M.; Lobkovsky, E. B.; Coates, G. W. J. Am. Chem. Soc. 1998, 120, 11018. Collins, T. J. The Presidential Green Chemistry Challenge Awards Program, Summary of 1999 Award Entries and Recipients, EPA744-R-00-001. in: US Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington, DC, 2000, p. 3.

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[9] [10]

[11] [12] [13] [14] [15] [16] [17]

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Draths, K. M.; Frost, J. W.; Anastas, P. T.; Williamson, T. C. (Eds.) Green Chemistry: Frontiers in Benign Chemical Syntheses and Processes, Oxford University Press, New York, 1998, Ch. 9, p. 150. Draths, K. M.; Frost, J. W. The Presidential Green Chemistry Challenge Awards Program, Summary of 1998 Award Entries and Recipients, EPA744-R-98-001. in: US Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington, DC, 1998, p. 3. Thomas, J. M. Chem. Eng. News. 2000, 78(27), 7. Vincent, J.-M.; Rabion, A.; Yachandra, V. K.; Fish, R. H. Angew. Chem. Int. Ed. Engl. 1997, 36(21), 2346. Fish, R. H. The Presidential Green Chemistry Challenge Awards Program, Summary of 1999 Award Entries and Recipients, EPA744-R-00-001. in: US Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington, DC, 2000, p. 14. Choudary, B. M.; Sateesh, M.; Kantam, M. L.; Rao, K. K.; Prasad, K. V. R.; Raghavan, K. V.; J. A. R. P. Sarma. Chem. Commun. 2000, 25. Stewart, J. D. The Presidential Green Chemistry Challenge Awards Program, Summary of 1998 Award Entries and Recipients, EPA744-R-98-001. in: US Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington, DC, 1998, p. 12. Raja, R.; Thomas, J. M.; Sankar, G. Chem. Commun. 1999, 525. Bal, R.; Sivasanker, S. Green Chem. 2000, 2, 106. Paciello, R.; Siggel, L.; Röper, M. Angew. Chem. Int. Ed. 1999, 38(13/14), 1920. Bandgar, B. P.; Kasture, S. P. Green Chem. 2000, 2, 154. Bandgar, B. P.; Kasture, S. P.; Tidke, K.; Makone, S. S. Green Chem. 2000, 2, 152. Simmons, M. S.; Anastas, P. T.; Williamson, T. C. (Eds.) Green Chemistry: Designing Chemistry for the Environment, American Chemical Society, Washington, DC, 1996, Ch. 10, p. 116. BHC Company. The Presidential Green Chemistry Challenge Awards Program, Summary of 1997 Award Entries and Recipients, EPA744-S-97-001. in: US Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington, DC, 1997, p. 2. Simmons, M. S.; Anastas, P. T.; Williamson, T. C. (Eds.) Green Chemistry: Designing Chemistry for the Environment, American Chemical Society, Washington, DC, 1996, Ch. 10, p. 121. Pharmacia and Upjohn Inc. The Presidential Green Chemistry Challenge Awards Program, Summary of 1996 Award Entries and Recipients, EPA744-K-96-001. in: US Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington, DC, 1996, p. 18. Margolin, A. L.; Delinck, D. L.; Whalon, M. R. J. Am. Chem. Soc. 1990, 112, 2849. Takayama, S.; Martin, R.; Wu, J.; Laslo, K.; Siuzdak, G.; Wong, C.-H. J. Am. Chem. Soc. 1997, 119, 8146. Lilly Research Laboratories. The Presidential Green Chemistry Challenge Awards Program, Summary of 1999 Award Entries and Recipients, EPA744-R-00-001. in: US Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington, DC, 2000, p. 5. Lesutis, H. P.; Gläser, R.; Liotta, C. L.; Eckert, C. A. Chem. Commun. 1999, 2063. Li, C.-J.; Anastas, P. T.; Williamson, T. C. (Eds.) Green Chemistry: Frontiers in Benign Chemical Syntheses and Processes, Ch. 14, Oxford University Press, New York, 1998, p. 234. Oakes, R. S.; Heppenstall, T. J.; Shezad, N.; Clifford, A. A.; Rayner, C. M. Chem. Commun. 1999, 1459. Zulfiqar, F.; Kitazume, T. Green Chem. 2000, 2, 137. Donlar Corporation. The Presidential Green Chemistry Challenge Awards Program, Summary of 1996 Award Entries and Recipients, EPA744-K-96-001. in: US Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington, DC, 1996, p. 5. Shi, F.; Gross, R. A.; Ashby, R.; Anastas, P. T.; Williamson, T. C. (Eds.) Green Chemistry: Frontiers in Benign Chemical Syntheses and Processes, Oxford University Press, New York, 1998, Ch. 11, p. 178.

Mara R. Livezey

4 Green chemistry and environmental justice in the biochemistry classroom Abstract: Publication of manuscripts that directly address justice in the chemistry discipline is of recent interest to the American Chemical Society, as shown in the 2021 Special Issue of the Journal of Chemical Education on Diversity, Equity, Inclusion, and Respect in Chemistry Education Research and Practice. This chapter extends this effort by describing three reflection activities for a biochemistry classroom that incorporate green chemistry and environmental justice themes. These activities relate to classroom content, and encourage students to push beyond what they are learning in class, to how science can impact people’s lives. In particular, students are provided the opportunity to read linked articles that discuss the impact of chemistry on various populations, then write a one- to two-paragraph reflection on the article. These reflective activities engage students in discussions of scientific ethics, racism, and socioeconomic status, and can also provide a way for students to think about their role as change-makers. Activities such as those described here can be a way to holistically develop our chemistry students and prepare them for careers as civic-minded chemists. The American Chemical Society (ACS) Committee on Environmental Improvement’s mission is “to advance sustainability thinking and practice across ACS and society for the benefit of earth and its people” [1]. As chemistry faculty and members of the ACS, we are able to, and should, contribute to this mission in meaningful ways within our classrooms on a daily basis. Indeed, there are an increasing number of publications describing the incorporation of green chemistry into chemistry curricula with the explicit purpose of increasing student knowledge of sustainability [2, 3]. Furthermore, the ACS Committee on Professional Training has released a guide framing ways to incorporate green chemistry throughout the chemistry curriculum [4]. Beyond simply developing students’ awareness of green chemistry, incorporation of sustainability into the chemistry curriculum provides an avenue for faculty to develop students holistically, as ethical-minded chemists. In particular, environmental justice seems an appropriate addition to discussions of green chemistry and sustainability, as its principles center diversity, equity, inclusion, and respect, values shared by the ACS [5, 6]. Briefly, environmental justice looks at sustainability through a lens of equity; all people should be equally protected from harmful environmental hazards and are invited to participate in the regulatory and decision-making processes at every level [7, 8].

Mara R. Livezey, Department of Chemistry and Biochemistry, University of Detroit Mercy, Detroit, MI 48221 https://doi.org/10.1515/9783110745658-004

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It was reported in 2007 that science, technology, engineering, and math (STEM) majors tend to be less civic-minded, as compared to their non-STEM counterparts when entering college [9]. In 2015, another study suggested that STEM students leaving college view working for social change as less important to their careers than nonSTEM students [10]. However, these data are averaged across all STEM students, and important differences can be seen when differentiating students based on reported identities. It has been noted that students with underrepresented identities, such as Black, Latinx, and female, tend to be more interested in working for social change, or are more motivated by altruism [10–12]. A more thorough incorporation of green chemistry, climate change, and environmental justice into chemistry curricula could increase the civic-mindedness of all graduating chemists, and better fulfill the Committee on Environmental Improvement’s mission. Well-placed environmental justice content across all chemistry courses can prompt students to actively engage the impact chemistry has on the world [13, 14]. Academic institutions can be producing not just chemists, but chemists who will contribute to the betterment of society [15]. Of course, in order to produce more civic-minded chemists, faculty must reorient and redesign their classrooms to contain environmental justice content [16]. Recent examples of such work in the chemistry classroom include a lab activity where students collected and measured the metal ion content of water samples in Baltimore [17] and a seminar class where students were asked to connect recent chemistry research to environmental racism [18]. Similar examples of incorporating social justice into the classroom exist for biochemistry as well, although the activities tend to relate more directly to human health. Two such activities include incorporating discussions of medical racism in the classroom [19] and urinalysis lab experiments that relate to prenatal health equity [20]. This chapter describes three reflection-based assignments suitable for a biochemistry class that directly incorporate environmental justice.

4.1 Course design and objectives The assignments described in this chapter were developed for students in 4,000-level biochemistry classes at the University of Detroit Mercy, located in Detroit, MI. Detroit Mercy is a Catholic institution in the Jesuit and Mercy traditions. Importantly, both the Sisters of Mercy and the Society of Jesus emphasize antiracism and environmental sustainability as critical concerns of their orders [21, 22]. During the first week of class, students are introduced to the Sisters of Mercy and the Society of Jesus so that they understand how the university mission will be incorporated into the class and homework assignments. Importantly, the students are also told at this time that some of these assignments will incorporate challenging topics like racism.

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The environmental justice assignments are incorporated into the first semester of a two-semester biochemistry series (CHM 4710), as well as a single-semester comprehensive course (CHM 4700). The course objectives for CHM 4710 are as follows: I. Predict the function of biologically important molecules based on their structure. II. Synthesize and explain how thermodynamics and kinetics underlie biological processes, enzymes, and metabolism. III. Determine the result of enzyme inhibition and allosteric effects and analyze data showing the same. Create hypothetical active sites for known biomolecules. IV. Be able to conceptualize and connect core biochemical pathways: glycolysis, citric acid cycle, and oxidative phosphorylation. V. Be able to apply learned knowledge to new biochemical phenomena, predict the result of mutations on known systems, and determine the broad effects of small changes within biological pathways. VI. Demonstrate an understanding of the impact of science on diverse populations. Students demonstrate objective VI in a series of homework reflection essays called “Mission Moments.” These assignments provide an opportunity to directly relate classroom content to green chemistry, climate change, and environmental justice. For each assignment, students are asked to read a linked article, and reflect by writing a oneto two-paragraph response to a given prompt. Students are reminded throughout the semester that assessment of written reflections is based on a good-faith effort and the quality of the response; alignment with the instructor’s opinions and political beliefs is not required to receive full marks.

4.2 Environmental justice activity: Flint water crisis The first environmental justice reflection aligns with the class content covering the physical and chemical properties of water. Included in the class is a review of noncovalent interactions and intermolecular forces, Coulomb’s law, and the hydrophobic effect. In this Mission Moment, students read an article that describes the $626 million settlement awarded to residents of Flint following the year-long lead contamination of Flint water (Table 4.1) [23]. They are then asked to reflect on whether the settlement is an adequate response to the Flint water crisis for the residents of that area. Later in the semester, students are reminded of the importance of metal ions in human physiology when learning about metal ion cofactors and enzyme mechanisms.

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Table 4.1: Flint water crisis mission moment prompt.a Question text After reading the above article, please comment on the following in one to two paragraphs. A monetary settlement has been reached that will provide funds to families that have been impacted by high levels of lead in Flint’s water. () Is this settlement justice for families with children who might have suffered irreversible damage? Why or why not? () What would you propose is an appropriate solution for families impacted by the flint water crisis? a

https://www.npr.org/2021/11/10/1054487544/judge-oks-flint-water-settlement-lead.

4.3 Green chemistry activity: the Bhopal disaster Another mission moment integrates with the class content covering enzyme inhibition and kinetics. In particular, the relevant class content covers competitive, uncompetitive, and mixed inhibitors, and their effects on enzyme activity. In the article, students read about the long-term health effects of the residents of Bhopal, their families, and their children on exposure to methyl isocyanate (Table 4.2) [24]. Students are then asked to reflect on the 12 principles of green chemistry, and discuss the responsibility of chemists for the chemistry they do through that lens [25]. Finally, students are asked to expand their reflection beyond personal responsibility, to the level of company and government oversight. This homework assignment further incorporates relevant biochemical content by asking students to determine the type of inhibition caused by methyl isocyanate, given hypothetical enzyme kinetics data.

Table 4.2: Bhopal disaster mission moment prompt.a Question text The article discusses the many impacts of the Bhopal disaster on those who were living during that time, and also those born after. In your one- to two-paragraph reflection about the article, make sure to touch on all of the following three questions. () To what extent are chemists responsible for the safety of the chemistry they do? Please relate this to the  principles of green chemistry you learned in organic chemistry, by choosing one principle to discuss. () To what extent is Union Carbide, now DOW chemical, responsible for this event? () To what extent are nations responsible for ensuring environmental justice for their citizens, and citizens of the world? a

https://www.theguardian.com/cities/2019/dec/08/bhopals-tragedy-has-not-stopped-the-urban-disasterstill-claiming-lives-35-years-on.

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4.4 Environmental justice activity: air pollution in urban settings The last mission moment is introduced when the class is learning about oxidative metabolism. The class content at this time covers glycolysis, and students are introduced to the phenomenon that cancer cells have increased glucose metabolism, compared to the normal tissue. Students read an article that describes how air tends to be more polluted with potentially carcinogenic particulate in neighborhoods that are of low socioeconomic status, or whose residents are largely Latinx, Asian, or Black (Table 4.3) [26]. Students are then asked to reflect on the impact of social power on exposure to air pollution. Table 4.3: Air pollution mission moment prompt.a Question text The above article describes the disproportionate impact that air pollution has on people of lower socioeconomic status. In the article, a number of factors are mentioned about why the impact is inequitable, for example, racist discrimination in housing and loans (redlining), and low education or income status. In one to two paragraphs, comment on how lack of social power caused by racism, education, or income can have significant, and long-lasting effects on human health. a

https://www.scientificamerican.com/article/people-poor-neighborhoods-breate-more-hazardous-par ticles/.

4.5 Discussion In order for our institutions to graduate ethical-minded chemists with a capacity to discern the impact of their field on people, faculty across all chemistry disciplines should incorporate materials into their classroom that integrate green chemistry and environmental justice. Exposure to such a material should have a positive influence on our students in a number of areas. For example, the reflective activities described in this chapter will introduce some students to topics they were not previously familiar with, and at the very least, should expand their awareness of the impact of chemistry on people. At most, writing reflective responses will allow students to develop ethically, practice civic-mindedness, and engage holistically with the subject of chemistry beyond class content. Arguably, students are already learning this in other elective courses such as humanities electives, but, ideally, we also scaffold these ideas into the chemistry curriculum so our students practice ethics and civic-mindedness within the context of our fields. Moreover, by asking students to reflect on what part they can play in promoting environmental justice, students might develop increased self-efficacy, confidence that their

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choices matter, and belief that their personal and professional choices can make a difference for others. Incorporation of environmental justice into the chemistry classroom may present challenges from student’s perspective. Students can assume that faculty are politically motivated, or are looking for students to align themselves with the faculty’s own personal belief system. Indeed, these are criticisms that the author has experienced. To mitigate this, students can be reminded of the ways that environmental justice content aligns with the institution’s mission. At Detroit Mercy, there is a clear connection between Jesuit and Mercy values, and environmental justice. At other institutions, it may be more prudent to cite ACS’s values of diversity, equity, inclusion, and respect, and sustainability [1, 5]. Students should also be made aware at the beginning of the term that the class material will include readings and reflections on topics such as racism. Warning students early on can help them mentally prepare for such topics and will ensure they are not taken by surprise later in the term. Importantly, students should also be periodically reminded that grading of environmental justice assignments is based on a good-faith effort, and not on whether the response matches the instructor’s own beliefs and opinions. Challenges may also exist for faculty who are new to discussions of sustainability, environmental justice, and racism, as these topics can sometimes be uncomfortable. Even so, faculty and students have the ability to rise to this challenge and work through the discomfort together. Inviting students into thinking of and building toward a future where environmental justice is practiced by all chemists is an opportunity we should not pass up as faculty. Possibly, the most rewarding part of engaging students in this type of reflective work is reading their responses. Following are excerpts from two such reflections. The first is in response to the Flint water crisis, and the second is in response to the Bhopal reading: I would propose that a larger compensation be allocated towards families, based on lifetime calculations of the effects of lead exposure (lost salary, medical costs, disabilities, etc.). Lead poisoning may cause problems year later, thus it is also important that the government is prepared to allocate funds to these people in the future. I would also propose that the government provide a strong plan demonstrating restructuring in the government hierarchy and policies regarding water to begin the healing process for citizens reassuring them that change is coming. In a very basic way, environmental justice is about the intersection of human rights, infrastructure and how people – rich and poor, living in rich or developing countries – equitably and sustainably access the resources and things they need to survive and prosper. Climate change, acid rain, depletion of the ozone layer, species extinction – all of these issues point to one thing: environmental health is a global issue that concerns all nations of the world. Now add environmental justice to the list.

Furthermore, faculty have the opportunity to engage their students with environmental justice at whatever level will be best for their class. Environmental justice can be integrated into one assignment, or all assignments. Additionally, faculty can

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create assignments that reflect their local neighborhood or city, the country, or the world. An exciting area of expansion would be to incorporate recent research into discussions of environmental justice. For example, Lu et al. recently described an enzyme that de-polymerizes plastics, and enzymatic degradation of organic polymers is of recent interest [27–29]. This could seamlessly integrate with class content on enzyme mechanisms, and would allow discussion of plastic production, recycling, and pollution. The climate change literature could be discussed alongside oxidative metabolism and could be expanded to address equity issues in the face of a warming climate [30–32].

References [1]

Committee on Environmental Improvement. American Chemical Society. https://www.acs.org/content/ acs/en/about/governance/committees/environmental-improvement.html (accessed 2022-06-22). [2] Aubrecht, K. B.; Bourgeois, M.; Brush, E. J.; MacKellar, J.; Wissinger, J. E. Integrating Green Chemistry in the Curriculum: Building Student Skills in Systems Thinking, Safety, and Sustainability. J. Chem. Educ. 2019, 96(12), 2872–2880, https://doi.org/10.1021/acs.jchemed.9b00354. [3] Herranen, J.; Yavuzkaya, M.; Sjöström, J. Embedding Chemistry Education into Environmental and Sustainability Education: Development of a Didaktik Model Based on an Eco-Reflexive Approach. Sustainability. 2021, 13(4), 1746, https://doi.org/10.3390/su13041746. [4] ACS CPT Supplement Green Chemistry in the Curriculum. [5] ACS Statement on Diversity, Equity, Inclusion and Respect. American Chemical Society. https://www.acs. org/content/acs/en/policy/washington-science/2021-public-comments/2021-acs-comments/2021deir-statement.html (accessed 2022-10-11). [6] Winfield, L. L.; Wilson-Kennedy, Z. S.; Payton-Stewart, F.; Nielson, J.; Kimble-Hill, A. C.; Arriaga, E. A. Addition to “Journal of Chemical Education Call for Papers: Special Issue on Diversity, Equity, Inclusion, and Respect in Chemistry Education Research and Practice. J. Chem. Educ. 2021, 98(3), 1057–1058, https://doi.org/10.1021/acs.jchemed.1c00163. [7] US EPA, O. Environmental Justice. https://www.epa.gov/environmentaljustice (accessed 2022-06-22). [8] Principles of environmental justice. National Black Environmental Justice Network. https://www.nbejn. com/projects (accessed 2022-06-22). [9] Nicholls, G. M.; Wolfe, H.; Besterfield-Sacre, M.; Shuman, L. J.; Larpkiattaworn, S. A Method for Identifying Variables for Predicting STEM Enrollment. J. Eng. Educ. 2007, 96(1), 33–44, https://doi. org/10.1002/j.2168-9830.2007.tb00913.x. [10] Garibay, J. C. STEM Students’ Social Agency and Views on Working for Social Change: Are STEM Disciplines Developing Socially and Civically Responsible Students? J. Res. Sci. Teach. 2015, 52(5), 610–632, https://doi.org/10.1002/tea.21203. [11] McGee, E.; Bentley, L. The Equity Ethic: Black and Latinx College Students Reengineering Their STEM Careers toward Justice. Am. J. Educ. 2017, 124(1), 1–36, https://doi.org/10.1086/693954. [12] Lederman, M. Teaching Science with the Social Studies of Science or Equity. J. Women Minor. Sci. Eng. 2005, 11, 3, https://doi.org/10.1615/JWomenMinorScienEng.v11.i3.40. [13] Lasker, G. A.; Mellor, K. E.; Mullins, M. L.; Nesmith, S. M.; Simcox, N. J. Social and Environmental Justice in the Chemistry Classroom. J. Chem. Educ. 2017, 94(8), 983–987. [14] Aoki, E.; Rastede, E.; Gupta, A. Teaching Sustainability and Environmental Justice in Undergraduate Chemistry Courses. J. Chem. Educ. 2022, 99(1), 283–290, https://doi.org/10.1021/acs.jchemed.1c00412.

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[18] [19] [20]

[21] [22] [23] [24] [25] [26]

[27]

[28] [29] [30] [31]

[32]

Mara R. Livezey

Beckwith, J.; Huang, F. Should We Make A Fuss? A Case for Social Responsibility in Science. Nat. Biotechnol. 2005, 23(12), 1479–1480, https://doi.org/10.1038/nbt1205-1479. Matlin, S. A.; Mehta, G.; Hopf, H.; Krief, A. One-World Chemistry and Systems Thinking. Nat. Chem. 2016, 8(5), 393–398, https://doi.org/10.1038/nchem.2498. Neu, H. M.; Lee, M.; Pritts, J. D.; Sherman, A. R.; Michel, S. L. J. Seeing the “Unseeable,” A StudentLed Activity to Identify Metals in Drinking Water. J. Chem. Educ. 2020, 97(10), 3690–3696, https://doi. org/10.1021/acs.jchemed.9b00553. Gerdon, A. E. Connecting Chemistry to Social Justice in a Seminar Course for Chemistry Majors. J. Chem. Educ. 2020, 97(12), 4316–4320, https://doi.org/10.1021/acs.jchemed.0c01043. Hollond, C.; Sung, R.-J.; Liu, J. M. Integrating Antiracism, Social Justice, and Equity Themes in a Biochemistry Class. J. Chem. Educ. 2021, https://doi.org/10.1021/acs.jchemed.1c00382. Clark, G. A.; Humphries, M. L.; Perez, J.; Udoetuk, S.; Bhatt, K.; Domingo, J. P.; Garcia, M.; Daubenmire, P. L.; Mansuri, N.; King, M. Urinalysis and Prenatal Health: Evaluation of a Simple Experiment that Connects Organic Functional Groups to Health Equity. J. Chem. Educ. 2020, 97(1), 48–55, https://doi.org/10.1021/acs.jchemed.9b00408. Mercy for Justice. Sisters of Mercy. Apostolic Preferences | The Society of Jesus. https://www.jesuits.global/uap/ (accessed 2022-10-11). Press, T. A. People Exposed to Lead in Flint, Mich., Water Will Get a $626 Million Settlement. NPR. 2021. Ellis-Petersen, H. “Bhopal’s Tragedy Has Not Stopped”: The Urban Disaster Still Claiming Lives 35 Years On. The Guardian. December 8, 2019. 12 Principles of Green Chemistry. American Chemical Society. https://www.acs.org/content/acs/en/ greenchemistry/principles/12-principles-of-green-chemistry.html (accessed 2022-10-13). News, C. K. Environmental Health. People in Poor Neighborhoods Breathe More Hazardous Particles. Scientific American. https://www.scientificamerican.com/article/people-poor-neighborhoods-breatemore-hazardous-particles/ (accessed 2022-10-13). Lu, H.; Diaz, D. J.; Czarnecki, N. J.; Zhu, C.; Kim, W.; Shroff, R.; Acosta, D. J.; Alexander, B. R.; Cole, H. O.; Zhang, Y.; Lynd, N. A.; Ellington, A. D.; Alper, H. S. Machine Learning-Aided Engineering of Hydrolases for PET Depolymerization. Nature. 2022, 604(7907), 662–667, https://doi.org/10.1038/ s41586-022-04599-z. Mohanan, N.; Montazer, Z.; Sharma, P. K.; Levin, D. B. Microbial and Enzymatic Degradation of Synthetic Plastics. Front. Microbiol. 2020, 11. A Better Plastic-Degrading Enzyme. CEN Glob. Enterp. 2022, 100(17), 6–6. https://doi.org/10.1021/cen10017-scicon2. Haines, A. Use the Remaining Carbon Budget Wisely for Health Equity and Climate Justice. Lancet. 2022, 400(10351), 477–479, https://doi.org/10.1016/S0140-6736(22)01192-8. Reckien, D.; Lwasa, S.; Satterthwaite, D.; McEvoy, D.; Creutzig, F.; Montgomery, M.; Schensul, D.; Balk, D.; Alam Khan, I.; Fernandez, B. Equity Environmental Justice, and Urban Climate Change. 2018. Khanal, S.; Ramadani, L.; Boeckmann, M. Health Equity in Climate Change Policies and Public Health Policies Related to Climate Change: Protocol for a Systematic Review. Int. J. Environ. Res. Public. Health. 2022, 19(15), 9126, https://doi.org/10.3390/ijerph19159126.

Mythreyi Sivaraman, Cole Radke, Weile Yan✶

5 Quantifying microplastics in beach sand and river sediment using thermal analytical methods Abstract: Microplastics are emerging contaminants that have gained significance in the recent years. To understand the generation, transport, and transformation of microplastics in the environment, it is important to be able to identify plastics by their type and quantify their levels in environmental matrices. This study reviewed existing thermal analytical techniques employed in microplastics research and discussed their advantages and limitations. As a case study, we examined microplastics in beach sand and river sediment samples collected at two locations in Massachusetts, USA using pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS). Multiple-step pretreatment processing based on size fractionation, density separation, wet peroxide oxidation, and solvent extraction was necessary to remove inorganic constituents and natural organic matter in samples prior to PY-GC-MS analysis. Pretreatment sequence was optimized separately for beach sand and river sediment as the latter carried very high levels of plant debris and organic matter. PET was identified in the fine fraction (< 100 μm) of the beach sand at 8.1 mg/kg and it was not detected in the medium size fraction (100 μm – 1.2 mm). This suggests the degradation of macro-plastics on beach due to UV exposure and mechanical abrasion caused by water and sand. For the river sediment sample, PET was detected in both the fine and medium fractions and the mass concentrations were on the order of 1 mg/kg. PP was also detected in both fractions of the river sediment at 0.1 – 0.3 mg/kg. The results validate the ability of PY-GC-MS in conjunction with appropriate pretreatments to quantitatively analyze low levels of microplastics in the coastal and terrestrial environments.

5.1 Introduction Due to high volumes of plastic usage and the ubiquitous presence of plastics in consumer products, the contamination of the environment with plastics has become an increasingly vexing situation. In particular, micro- and nanoplastics, defined as plastic debris smaller than 5 mm and 1 µm in size [1], respectively, have been detected in all environmental media across the world and are considered an imminent environmental issue. They are ubiquitously occurring in terrestrial, marine, and freshwater environments [2]. The ✶

Corresponding author: Weile Yan, Department of Civil and Environmental Engineering, University of Massachusetts Lowell, Massachusetts, United States of America, e-mail: [email protected] Mythreyi Sivaraman, Cole Radke, Department of Civil and Environmental Engineering, University of Massachusetts Lowell, Massachusetts, United States of America https://doi.org/10.1515/9783110745658-005

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distribution of micro- and nanoplastics in these different environments remains unclear. Better understanding on the occurrence, fate, transport, and interaction of these plastic debris in these different environments becomes significant. Once that understanding is obtained it would be easier to extrapolate the potential risks micro- and nanoplastics pose to living organisms and human health. The first step therefore in understanding the occurrence is identification and quantification of microplastics in these environments [3]. Quantification and identification of microplastics in environmental matrices are challenging due to high concentrations of inorganic solids, natural organic matter, and other debris [4]. Pretreatment methods facilitate the purification and extraction of microplastics from their original matrices. This in turn is expected to improve identifying microplastics. Wet peroxide oxidation, density separation, and enzymatic digestion are the pretreatment methods used extensively for separation of microplastics. Wet peroxide oxidation is used to remove organics and biological matter and preconcentrate microplastics from environmental matrices [5]. During wet peroxide oxidation, samples are digested with Fenton’s reagent, typically consisting of ferrous sulfate and hydrogen peroxide [16]. The method does not affect microplastic debris and is a necessary step for samples with high organic carbon content such as wastewater samples, soils, and river or marine sediments [2, 4, 6–10]. Density separation uses the density differences between microplastics and inorganic background constituents (e.g., sand, silt, and clay) to separate plastics from the sample matrices. Density separation is usually performed in a fluid medium of a suitable density. Ideally, the density of the fluid medium should be higher than common plastics of interest and lower than the background solids, and for this reason, most studies use Table 5.1: Density separation methods used in sample processing for microplastics analysis. Medium used in density separation

Type of samples

References

Sodium chloride (NaCl)

River sediment Marine sediment Shoreline debris Sea salt Surface soils Fish

[, –]

Sodium iodide (NaI)

Marine sediment Fish Wastewater

[, , ]

Zinc chloride (ZnCl)

Artificial samples Wastewater Marine sediments

Sodium metatungstate (HNaOW)

Riverbed sediments Artificial samples

[, ]

[]

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concentrated salt solutions. Of the different media suggested in literature and described in Table 5.1, zinc chloride is low-cost, easily recoverable, and chemically more benign than tungstate salts and has a density significantly above the common plastics. Upon pretreatment, microplastics are amenable to detection using visual or microscopic inspection based on their physical appearance (e.g., shape, size, color, and surface morphology). As particle size decreases, properties used in visual or microscopic detection are less distinctive and may lead to significant errors [5]. Identification of chemical structure is therefore indispensable [15]. Currently, identifying plastics in environmental samples is achieved with spectroscopic and thermoanalytical methods. Vibrational spectroscopic methods such as Fourier transform infrared (FTIR) and Raman spectroscopy can inform the type of plastics [11]. More recently, the advent of micron-sized FTIR and Raman probes that can conduct automated scans across a large area in search for synthetic polymers has given rise to μ-FTIR or μ-Raman microscopic spectroscopy [17, 18]. However, the analytical microscope instruments are of high costs and the analysis speed is relatively slow, especially when high resolution scans are needed to identify smaller particles [5]. They generate information related to the size and the number of plastic particles but cannot quantify the mass concentration in environmental samples. Currently, the size limits of FTIR (>20 µm) and Raman (>1 µm) detection imply that they are not able to detect smaller-sized plastic debris, leading to underestimation errors [3]. For complex matrices such as biosolids and digestion residues, laborious pretreatment methods to remove potential interferences caused by the high background organic matter are essential [1]. Thermoanalytical techniques provide an alternative for quantification and identification of microplastics. Unlike spectroscopic techniques, these methods are not sizedependent. These techniques are considered more robust against impurities and potential interference from environmental matrices [3]. The most applied thermoanalytical techniques are thermogravimetric analysis (TGA, often hyphened with mass spectrometry or other analytical techniques), thermal desorption-gas chromatography-mass spectrometry (TED-GC-MS), and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). In general, thermal analysis requires the pretreatment of the environmental samples to remove background organics and concentrate trace levels of microplastics to facilitate their identification. These pretreatment can be laborious and, if not properly designed, inefficient in separating microplastics from other sample constituents, and introducing errors [1]. Table 5.2 summarizes pretreatment steps and the pertinent analysis conditions employed in recent microplastic studies that used thermal-analytical techniques, and the advantages and drawbacks of each technique are briefly discussed below. TGA is a method in which the mass of a sample is measured over time as the sample experiences a temperature gradient. This measurement provides information about physical changes such as phase transitions, absorption, and adsorption/desorption as well as chemical transformation including chemisorption, thermal decomposition, and solid-gas reactions [22]. Since polymers such as PE and PP have distinct phase transition and thermal degradation behavior, TGA has been employed in polymer science to measure the purity of plastics [6]. When coupled with differential

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Table 5.2: Summary of thermal analytical methods for plastic analysis in the literature. Analysis method

Type of samples

Pretreatment involved

Key analysis conditions

Pyrolysis Single-shot pyrolysis

Soil spiked with MPs River water Seawater Influent and effluent of WWTP

Solvent extraction Cloud point extraction Methanol cleanup Flocculation Wet peroxide oxidation

Pyrolysis: – °C

[, ]

Pure plastics Biosolids Marine sediment

Pressurized liquid extraction Density separation

First shot: – °C Second shot: ~ °C

[, ]

Sieving Wet peroxide oxidation Density separation Enzymatic digestion Degreasing with petrol

Reagent: TMAH Pyrolysis:  °C Internal standard (IS): dodecyl-,,,,,,,octahydro anthracene, anthracene d-, androstane, cholanic acid

Filtration Density separation Wet peroxide oxidation

Temperature range: –, °C IS: cysteine

[, ]

Temperature range: – °C

[, ]

Double-shot pyrolysis

Thermochemolysis Pure plastics Sea salt Marine sediment Fish spiked with MPs Riverbed sediment

Thermogravimetric analysis

Artificial MPs Wastewater effluent Soil spiked with MPs

Thermodesorption

Artificial MPs Cryomilling Solid and liquid residues from a biogas plant River sediments

References

[, , ]

scanning calorimetry (DSC), a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and a reference is measured as a function of temperature, TGA-DSC was able to identify and quantify the presence of microplastics in wastewater samples [6]. TGA-DSC analysis does not require

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sophisticated instrumentation or complex sample cleaning steps [19]. However, overlapping transition temperatures of certain polymers may limit the identification and estimation of some microplastics. In addition, phase transition temperatures are affected by particle sizes and the presence of additives, and this can complicate data analysis for environmental samples that carry mixture of plastics of varying characteristics [19]. The method also suffers poor accuracy for low levels (1.2 mm), medium (100 μm–1.2 mm), and fine ( 0.99). Apart from direct pyrolysis of particulate plastics, solvent extraction of plastics has gained significance due to the ease of preparation of plastic standards over a large range of mass quantities, particularly at the lower end where standards may be prepared via dilution, and the ability to extract plastics selectively leaving behind background constituents in environmental samples. This approach has led to higher quality of calibration and improved LOD and LOQ values. Measurement inaccuracy caused by weighing microamounts of plastic standards for direct pyrolysis is minimized by the use of solvent extraction. Various solvents have been used in previous studies. 1,2,4-TCB was attempted by one group to extract PS, PE, and PP [3]. All three plastics were extracted together and good calibration results (r2 > 0.99) were attained for each of the plastics, suggesting that the individual plastics analyzed at similar levels did not interfere with each other during pyrolysis. However, extending this method to other plastics is difficult due to limited dissolution in 1,2,4-TCB. Another solvent used in the literature to dissolve polymers is DCM. At room temperature, DCM dissolves PS readily but not

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other polymers (Table 5.3). Extraction efficiency was improved via pressurized liquid extraction [1] or microwave-assisted extraction [32]. Pressurized liquid extraction was performed at 180 °C and 1,500 psi to partially extract PS, PMMA, and PC. Microwaveassisted solvent extraction with DCM was performed at up to 80 °C with 600 W irradiation powder [32]. This method was effective for the extraction of PS and several phthalates, but no significant dissolution of HDPE and PP in DCM was achieved. Calibrations of the latter polymers had to resort to direct pyrolysis [32]. Solvent mixtures were used in some studies [33]. A mixture of DCM and tetrahydrofuran was used for extracting PS, PVC, PMMA, and ABS copolymer. For Nylon 6, Nylon 66, and PET, hexafluoroisopropanol (HFIP) was used. PE and PP were in solid state and introduced with inorganic diluent silica. Notably, these solvents are not able to extract some common plastics widely used in consumer products and likely found in the environment such as PET. In this study, we used 2-chlorophoenol to extract plastics because of its availability and its ability to dissolve a variety of common plastics. As shown in Table 5.3, 2chlorophenol is able to dissolve PET, PS, PVC, and Nylon 66 at room temperature. We had initially attempted to set up PET calibration via direct pyrolysis of commercial PET powder (from Sigma Aldrich); however, the quality of calibration is poor due to limited accuracy of the weighing balance. This is consistent with the observations of other research groups that attempted calibration of solid plastic standards [5, 25]. By preparing PET standards in 2-chlorophenol followed by double-shot pyrolysis, linear response of m/z 105 signal (normalized by the signal of deuterated PS as the IS) vs. PET mass in the range of 1–6 μg was achieved (Figure 5.3). The signal-to-noise ratio

Normalized Abundance

(a)

PET m/z 105

2.0 1.5

y = 0.2862x R² = 0.991

1.0 0.5

0.0

0

(b)

8

PP m/z 126

2.E+06 Abundance

2 4 6 Mass pyrolyzed, ug

2.E+06 1.E+06

y = 45,189x R² = 0.988

5.E+05 0.E+00

0

10 20 30 Mass pyrolyzed, ug

40

Figure 5.3: Calibration results of (a) PET and (b) PP.

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suggests that the lower end of the range can be pushed down further, and this coupled with the concentration effect of solvent evaporation and sample pretreatment operations enables reliable detection of PET at environmentally relevant concentrations (mg/kg or lower). The quality of the linear fit (r2 > 0.99) and LOQ exceed those obtained in studies that either directly pyrolyze PET or use other solvents such as HFIP for PET extraction [1, 32, 33]. Previous studies indicate that calibration using a plastic standard mix is not preferred due to interference arising from interactions among pyrolysis products. Performing calibrations with individual plastic standards is a better practice and is adopted in this study. Similar to PET, linear responses of PS, PVC, and Nylon 66 were obtained using standards prepared in 2-chlorophenol (results not shown). Our ongoing work is extending the calibration ranges of these plastics to below 1 μg. Unlike DCM or HFIP, which can only dissolve a limited set of plastics at room temperature and requires multiple extraction steps to dissolve plastics of common interest [1, 32, 33], the use of 2-chlorophenol can effectively simplify extraction to a single-step process involving one solvent, thereby reducing operation effort and solvent use in microplastic analysis. Polyolefins including PE and PP are resistant to solvent extraction even at an elevated temperature or pressure. We followed the method of solvent extraction with 1,2,4-TCB as suggested in a prior study [3]. Nonetheless, our data indicated minimal solubility of PE in 1,2,4-TCB even as we tried to extend extraction time to 4 h at 120 °C (note that a slightly higher temperature, 140 or 160 °C was used in the cited study). Given this result, PE and PP were calibrated through direct pyrolysis of standards. Minute portions of the standards were created by depositing one to several individual pieces of 250 µm PE powder or 1 cm strands of thin PP fibers in the sample cups. Using this method and m/z 55 as the PE quantifier, good calibration result was achieved. However, as will be noted later, significant interference caused by pyrolysis products of fatty acids and wax of natural origins in environmental samples hampers PE quantification. For PP, the calibration curve was constructed using m/z 126 as the quantifier, which gave a robust linear fit in the range of 2–30 μg (r2 = 0.99) as shown in Figure 5.3. The quality of PP and PE calibrations is consistent with other studies [1, 32, 33].

5.3.2 Results of beach sediment samples This choice of 2-chlorophenol as the solvent offers some advantages for plastic standard calibration as well as extracting environmental samples. 2-Chlorophenol is of low volatility with a boiling point of 175 °C, which is lower than the melting temperatures of most plastics analyzed, and it is immiscible with water. The density of 2chlorophenol is 1.26 g/ml higher than most common plastics except for PVC and PET. In contrast, DCM is highly volatile with a boiling point of 39.6 °C and is a known carcinogen. As mentioned before, DCM extraction requires pressurized conditions or microwave heating, and this adds to the safety concerns of sample handling [32, 33].

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Since 2-chlorophenol was able to dissolve most of the common plastics as shown in Table 5.3, it reduced the need for sequential solvent extraction as used in previous studies. For instance, Castelvetro et al. [21] used sequential solvent extraction to analyze microplastics in beach sand obtained from northern Tuscany and lake sediments from Lake Bracciano both in Italy. The extraction steps constitute a lengthy procedure in the sequence of DCM extraction (to isolate PS and low molecular-weight oxidized polyolefin fragments for SEC analysis), xylene (to extract high molecular-weight PE and PP for FTIR or Py-GC-MS analysis), acid hydrolysis (to identify Nylon6 and Nylon 66 by HPLC after derivatization), and alkaline depolymerization (to identify PET via HPLC) [21]. PS and PET were quantified for the beach sand samples after the complex pretreatment process. In comparison, the use of 2-chlorophenol at room temperature eliminates the need for multiple solvents, thereby reducing the complexity in sample processing. Each additional processing stage could introduce contamination or loss of analytes. The need for using different instrumentation for quantifying different plastics could be avoided in our process flow. Figure 5.4 indicates the concentration of PET found in the fine and medium fractions of the surface layer (0–5 cm deep) of Salisbury Beach. PET was detected in the fine fraction (particle size < 100 μm) at about 8.1 mg/kg. PET was not detected in the

Figure 5.4: Comparison of the MS spectra of a sediment sample that received (a) nonoptimized pretreatment and (b) optimized pretreatment prior to Py-GC-MS analysis.

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medium fraction. One objective of analyzing plastic debris in environmental samples was to understand the size distribution of plastic pollutants. The detection of a higher quantity of PET on the surface than in the medium fraction indicates that the macrosized, discrete plastics that were originally released from anthropogenic sources were degraded into finer pieces by different forces of nature. Constant fragmentation of discrete plastics disposed on the beach may occur due to exposure to the sunlight (UV) and mechanical stress and friction caused by water and sand. Other studies that used lab simulated UV and mechanical stress observed surface abrasions on plastic, particularly with the concerted effects of UV and mechanical attrition together [34]. The fine fraction could also be brought onto the surface by the regular tidal activities on the beach or transported around in air. It can be confirmed that the size of the plastics plays a significant role in its distribution in the environment. PS was detected in the beach sand as well; however, its quantitation was complicated by the presence of a small quantity of PS impurities in the IS. Other plastics were not identified in the beach sand samples. The results obtained for PET in the beach sand samples had high variability between replicates. Relatively large standard deviations among subsamples were noted in other studies, suggesting the need for larger sample sizes and sample replicates [21]. When the size of the plastic analyzed is larger, visual techniques can work complementary with thermal analysis methods to give a clearer picture of all plastics detected. However, as the size of particles of interest decreases to below ca. 100 μm, the quantification capability through visual inspection is severely constrained. This is where the use of an appropriate organic solvent to extract plastics can enable more accurate quantification of plastic pollutants

5.3.3 Results of river sediment samples The river sediment sample carried a significantly higher amount of natural organic matter than the beach sand sample. The river sediment sample appeared dark in color and clumpy in texture. Initially, the same sample pretreatment protocol employed for the beach sand samples was applied to processing the river sediment sample. The dense presence of organic carbon in the river sediment sample manifests in almost every stage of sample processing. Clumping was observed during sieving and various filtration operations. ZnCl2 solution for density separation became turbid after single use, preventing reuse of this highly concentrated metal solution. In comparison, the bulk portion of the ZnCl2 solution was clear after processing beach sand samples and was reused by two times filtration through 0.2 μm filter paper. Wet peroxide oxidation reactions were vigorous, which confirms high organic content in the river sediments. Figure 5.4 shows MS spectrum acquired during Py-GC-MS analysis of the sample processed using the original unoptimized pretreatment protocol. It reveals high background interference, and it was difficult to identify plastics; however, the

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spectrum indicated the presence of di-tertiary butyl phenol (m/z 191), a plastic additive and thermal degradation product of commonly used UV stabilizers. Although the presence of di-tertiary butyl phenol may indirectly infer the presence of plastics, it does not provide further info regarding the type and quantity of plastics present in the sample. Due to concern of high organic carbon content, Py-GC-MS was not performed on the solid residue after solvent extraction. We also evaluated sequential solvent extraction using DCM and 2-chlorophenol, but this did not help to eliminate the high background. To reduce the influence of background natural organic matter, sample pretreatment process was optimized. Additional steps were added to the flow including homogenization, ethanol disinfection, and one round of density separation using ethanol, and town rounds of density separation using ZnCl2, one before and one after wet peroxide oxidation (Figure 5.2). Specifically, homogenization was added to reduce the formation of clumps, as aggregates prevent complete contact with the subsequent separation/reaction media. Ethanol disinfection serves to prevent biomass growth during sample handling. Additionally, it helps to remove light organic debris such as leaves and plant tissue and waxy substances that bind particles together. The samples were dried and sieved to create different size fractions, after which ethanol density separation was used to remove any remaining discrete floating organic matter. As a result, wet peroxide oxidation was a less intense reaction compared to the un-optimized flow. The second density separation after WPO helped with further reducing environmental matrix. After solvent extraction with 2-chlorophenol, the solvent extract and solid phases were subjected to thermal analysis separately. Figure 5.4 shows the MS spectrum of the sample receiving the improved sample pretreatment flow (note that both Figures 5.4 and 4 are from analysis of the solvent extract). The background signals were significantly reduced, which enables identifying and quantifying microplastics with higher confidence for the river sediment sample. The Py-GC-MS results obtained using the optimized sample pretreatment protocol are summarized in Figure 5.5. PET and PP were identified in both the fine and medium fractions. The amount of PET detected in the fine fraction was 3.1 mg/ kg and the amount quantified in the medium fraction was 1.0 mg/kg. The PP in the fine fraction was 0.14 mg/kg and the medium fraction is 0.27 mg/kg. While a higher amount of PET was found in the fine fraction, the amount of PP in medium fraction is slightly higher than in the fine fraction. Prior studies have used to TED-GC-MS to analyze samples of high organic content. While plastics such as PE and PS had been qualitatively observed, quantification was proven difficult [12]. The application of Py-GC-MS analysis coupled with well-designed pretreatment greatly expands the ability of thermal analysis method to complex environmental samples. After solvent extraction, the solid residue was analyzed for identifying and quantifying PE and PP. Analysis of solid residue was found to be more challenging than the solvent extract due to the presence of remaining background organic matter not removed by sample pretreatment. Another reason is related to the pyrolysis by-products of PE and PP being short-chain alkanes and alkenes, which may also come from natural

5 Quantifying microplastics in beach sand and river sediment

Concentration, mg/kg

100.00

(a)

PET

10.00 1.00 0.10

0.01

N.D.

0.00

10.00 Concentration, mg/kg

71

Fine

Medium