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Module 3: Evaluation of Alternative Reaction Pathways Chapters 7 and 8

This module covers the educational goals and topics related to evaluating alternative reaction pathways in chemical engineering. It explores green chemistry concepts, such as atom efficiency and environmental impact assessment, and introduces a green chemistry expert system. The module also includes case studies on adipic acid and maleic anhydride synthesis.

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Module 3: Evaluation of Alternative Reaction Pathways Chapters 7 and 8

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  1. Module 3: Evaluation of Alternative Reaction PathwaysChapters 7 and 8 David T. Allen Department of Chemical Engineering University of Texas at Austin

  2. Module 3: Outline • Educational goals and topics covered in the module • Potential uses of the module in chemical engineering courses • Green chemistry concepts - atom efficiency • Tier 1 environmental impact assessment • Green chemistry expert system (software) • Adipic acid and maleic anhydride cases

  3. Module 3: Educational goals and topics covered in the module Students will: • understand the hierarchical design-for-environment approach for chemical processes • learn qualitative and quantitative methodologies for Green Chemistry • be able to evaluate feedstocks, solvents, and alternative reaction pathways; both economically and environmentally.

  4. Module 3: Potential uses of the module in chemical engineering courses • Design course: Green Chemistry concepts and a screening of chemical products and raw materials on the basis of economics and environmental impacts • Reactor design course: Waste and risk minimization approaches

  5. Module 3: Hierarchical design process for pollution prevention

  6. Module 3: Green Chemistry - Ch 7 • Guiding principles for reactions • Simplicity • Safety • High yield and selectivity • High energy and atom efficiency • Use of renewable resources • Recyclable reagents and raw materials

  7. Module 3: Feedstocks and solvents • Important considerations • Human / ecosystem health properties • Bioaccumulative? • Persistent? • Toxic? • Global warming, Ozone depletion, Smog formation? • Flammable or otherwise hazardous? • Renewable or non renewable resource? • Life cycle environmental burdens? - Ch 13, 14

  8. Module 3: Alternative choices: raw materials Benzene • fossil fuel source • carcinogenic Glucose • renewable source • non-toxic

  9. Module 3: Alternative choices: Solvents Supercritical CO2 Non-toxic, non-flammable, renewable sources Selectivity enhancement with SC CO2 Water as alternative solvent (as a co-solvent with an alcohol) Reaction rate enhancements

  10. Module 3: Synthesis pathways

  11. Module 3: Atom and Mass Efficiency:magnitude of improvements possible Atom Efficiency - the fraction of starting material incorporated into the desired product - C6H5-OH+ NH3 C6H5-NH2 + H2O • Carbon - 100% • Hydrogen - 7/9 x 100 = 77.8% • Oxygen - 0/1 x 100 = 0% • Nitrogen - 100% Mass Efficiency (Basis 1 mole of product) C6H5-OH+ NH3 C6H5-NH2 + H2O Mass in Product = (6 C) (12) + (7 H) x (1) + (0 O) x 16) + (1 N) x (14) = 93 grams Mass in Reactants = (6 C) (12) + (9 H) x (1) + (1 O) x 16) + (1 N) x (14) = 111 grams Mass Efficiency = 93/111 x 100 = 83.8%

  12. Module 3: Software explorationGreen Chemistry Expert System TOPIC AREAS • Green Synthetic Reactions - search a database for alternatives • Designing Safer Chemicals - information on chemical classes • Green Solvents/Reaction Conditions - alternative solvents / uses - solvent properties

  13. Module 3: Software demonstration Green Chemistry Expert System search Green Synthetic Reactions for adipic acid references

  14. Module 3: Adipic Acid SynthesisTraditional vs. New Traditional Route - from cyclohexanol/cyclohexanone Cu (.1-.5%) C6H12O+ 2 HNO3 + 2 H2O C6H10O4 + (NO, NO2, N2O, N2) V (.02-.1%) 92-96% Yield of Adipic Acid • Carbon - 100% • Oxygen - 4/9 x 100 = 44.4% • Hydrogen - 10/18 x 100 = 55.6% • Nitrogen - 0% Product Mass = (6 C)(12) + (10 H)(1) + (4 O)(16) = 146 g Reactant Mass = (6 C)(12) + (18 H)(1) + (9 O)(16) + (2 N)(14) = 262 g Mass Efficiency = 146/262 x 100 = 55.7% hazardous global warming ozone depletion Davis and Kemp, 1991, Adipic Acid, in Kirk-Othmer Encyclopedia of Chemical Technology, V. 1, 466 - 493

  15. Module 3: Adipic Acid SynthesisTraditional vs. New New Route - from cyclohexene Na2WO4•2H2O (1%) C6H10 + 4 H2O2 C6H10O4 + 4 H2O [CH3(n-C8H17) 3N]HSO4 (1%) 90% Yield of Adipic Acid • Carbon - 100% • Oxygen - 4/8 x 100 = 50% • Hydrogen - 10/18 x 100 = 55.6% Product Mass = (6 C)(12) + (10 H)(1) + (4 O)(16) = 146 g Reactant Mass = (6 C)(12) + (18 H)(1) + (8 O)(16) = 218 g Mass Efficiency = 146/218 x 100 = 67% Sato, et al. 1998, A “green” route to adipic acid:…, Science, V. 281, 11 Sept. 1646 - 1647

  16. Module 3: Maleic Anhydride SynthesisBenzene vs Butane - Mass Efficiency Benzene Route (Hedley et al. 1975, reference in ch. 8) V2O5 2 C6H6 + 9 O2 2 C4H2O3 + H2O + 4 CO2 (air) MoO3 95% Yield of Maleic Anhydride from Benzene in Fixed Bed Reactor Butane Route (VO)2P2O5 C4H10 + 3.5 O2 C4H2O0 + 4 H2O (air) 60% Yield of Maleic Anhydride from Butane in Fixed Bed Reactor Felthouse et al., 1991, “Maleic Anhydride, ..”, in Kirk-Othmer Encyclopedia of Chemical Technology, V. 15, 893 - 928

  17. Module 3: Maleic Anhydride SynthesisBenzene vs Butane - Summary Table 1 Rudd et al. 1981, “Petroleum Technology Assessment”, Wiley Interscience, New York 2 Chemical Marketing Reporter (Benzene and MA 6/12/00); Texas Liquid (Butane 6/22/00) 3 Threshold Limit Value, ACGIH - Amer. Conf. of Gov. Indust. Hyg., Inc. , www.acgih.org 4 Toxicity Weight, www.epa.gov/opptintr/env_ind/index.html and www.epa.gov/ngispgm3/iris/subst/index.html 5 ChemFate Database - www.esc.syrres.com, EFDB menu item

  18. Module 3: Maleic Anhydride SynthesisBenzene vs Butane - Tier 1 Assessment Benzene Route Butane Route

  19. Module 3: Maleic Anhydride SynthesisBenzene vs Butane - Tier 1 Assessment Benzene Route Butane Route

  20. Module 3: Recap • Educational goals and topics covered in the module • Potential uses of the module in chemical engineering courses • Green chemistry concepts • Tier 1 environmental impact assessment • Green chemistry expert system (software) • Adipic acid and maleic anhydride cases

  21. Module 3: Explore Green Chemistry Expert System search Green Solvents/Reaction Conditions Designing Safer Chemicals

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