The E factor at 21. Roger A. Sheldon Delft University of Technology

Transcription

1 The E factor at 21 Roger A. Sheldon Delft University of Technology 1

2 The E factor at 21 Outline 1. Origins of the E factor 2. Green chemistry, catalysis & sustainability 3. Suspect solvents 4. Biocatalysis 5. The bio-based economy 6. The metrics of sustainability 7. Conclusions & prospects 2

3 Phloroglucinol Synthesis anno 1980 CH 3 COOH O 2 N NO 2 K 2 Cr 2 O 7 O 2 N NO 2 Fe/HCl H 2 N NH 2 HO aq.hcl OH H 2 SO 4 / SO 3 - CO 2 ΔT NO 2 TNT NO 2 NH 2 Ca. 40kg of solid waste per kg phloroglucinol O H phloroglucinol HO OH O H product MW = 126 > 90 % yield Selective? Efficient? + Cr 2 (SO 4 ) 3 + 2KHSO 4 + 9FeCl 2 + 3NH 4 Cl + CO 2 + 8H 2 O byproducts Atom Utilisation = 126/2282 = ca. 5 % E Factor = ca. 40 To measure is to know Lord Kelvin 3

4 Reaction Stoichiometry and Atom Economy 4

5 Conclusion? A new paradigm was needed for efficiency in organic synthesis From the traditional one of chemical yield to one that assigns value to waste elimination and avoiding toxic/hazardous materials An environmental factor was missing 5

6 Green (Clean) Chemistry Green chemistry efficiently utilises (preferably renewable) raw materials, eliminates waste and avoids the use of toxic and/or hazardous solvents and reagents in the manufacture and application of chemical products. Anastas & Warner, Green Chemistry : Theory & Practice,Oxford Univ. Press,New York,1998 Sheldon, Arends and Hanefeld, Green Chemistry and Catalysis, Wiley, New York,

7 Green (Clean) Chemistry Green chemistry is pollution prevention not end-of-pipe remediation Environmental pollution is an incurable disease. It can only be prevented. Barry Commoner The Closing Circle,

8 What is Sustainability? Meeting the needs of the present generation without compromising the needs of future generations to meet their own needs Making every decision with the future in mind Profit People Planet Brundtland Report, Our Common Future,

9 The Sustainability Venn Diagram Social (People) Equitable Sustainable Economic (Profit) Bearable Viable Environment (Planet) 9

10 Green Chemistry Waste minimization Environmentally acceptable solvents, reagents and end-products Renewable feedstocks Products & processes The Bio-Based Economy - Biomass as feedstock - Biodegradable products - (Bio)catalytic conversions 10

11 E Factor = kg waste/kg product Tonnage E Factor Oil Refining <0.1 Bulk Chemicals <1-5 Fine chemical Industry >50 Pharmaceutical Industry >100 Another aspect of process development mentioned by all pharmaceutical process chemists who spoke with C&EN is the need for determining an E Factor. A. N. Thayer, C&EN, August 6, 2007, pp R.A.Sheldon, Chem & Ind, 1992, 903 ; 1997, 12 11

12 The E factor (E)verything but the Product Is the actual amount of all waste formed in the process, including solvent losses and waste from energy production (c.f. atom utilisation is a theoretical nr.) E = [kgs raw materials- kgs product]/[kgs product] A good way to quickly show (e.g. to students) the enormity of the waste problem What about the process water? Only if it needs to be treated 12

13 Metrics of Green Chemistry MI = E = E factor Total mass of waste Mass of final product Mass intensity (MI) Total mass in process Mass of product Atom efficiency (AE) AE (%) = m.w of product x 100 Σ m.w. of reactants Reaction mass efficiency (RME) RME(%) = Mass of product C x 100 Mass of A + Mass of B Mass Productivity (MP) Carbon efficiency (CE) MP = Mass of product Total mass in process CE(%) = Carbon in product x 100 Total carbon in reactants Effective mass yield (EMY) EMY(%) = Mass of product x 100 Mass of hazardous reagents 13

14 The Goal Is Zero E-factor as a green chemistry metric E-factor M&M model Industry segment 0.1 Oil refining 1 Bulk Chemicals & Polymers Fine Chemicals 250 Pharmaceuticals & Electronics Irvin J. Levy Professor of Chemistry Gordon College, Wenham, MA E-factor = mass of waste mass of product E-factor = (mass of inputs - mass of outputs) mass of product 14

15 On the Way Towards Greener Processes, as Quantified by E Factors B. H. Lipshutz, N. A. Isley, J. C. Fennewald, E. D. Slack 15

16 The Environmental Impact EQ EQ = E(kg waste) Q Q = Unfriendliness Multiplier e.g. NaCl : Q = 1 ( arbitrary) Cr salts : Q = 1000? There are many shades of green! Quantification of Q R.A.Sheldon, Chem & Ind, 1992, 903 ; 1997, 12 16

17 Environmental Assessment Tool for Organic Syntheses EATOS Combines raw material efficiency with LCA and economic indicators - Mass and Energy Flow - Environment, Health and Safety - Persistence, bioaccumulation and toxicity (PBT) - Costs J. O. Metzger and M. Eissen, Chem. Eur. J. 8, (2002) 17

18 Environmental Assessment Tool for Organic Syntheses EATOS 18

19 Major Sources of Waste Stoichiometric Reagents - Acids & Bases - Oxidants & reductants - Na 2 Cr 2 O 7, KMnO 4, MnO 2 - LiAlH 4, NaBH 4, Zn, Fe/HCl Solvent losses ( 85% of non-aqueous mass) The Solution : Atom & step economic catalytic processes in alternative reaction media (the best solvent is no solvent) 19

20 Bridging the Gap J. J. Berzelius Organic Chemistry (1807) Catalysis (1835) Urea synthesis 1828 ( Wöhler ) First synthetic dye 1856 Aniline purple (Perkin) Dyestuffs Industry (based on coal-tar) ca Catalysis definition (Ostwald) Catalytic Hydrogenation (Sabatier) ca Petrochemicals 1936 Catalytic cracking 1949 Catalytic reforming 1955 Ziegler-Natta catalysis Fine Chemicals Bulk Chemicals & Polymers Catalysis in Organic Synthesis 20

21 The Ideal Synthesis 100% Yield One Step Simple & Safe Economical in Time & Waste Environmentally Acceptable - atom economy - step economy - human economy Urea Taxol Apoptolidine s 2005 #Steps Shorten the synthesis or change the target N O 13 steps 1. Ni cat. 2. H 2 / cat. + Wilstatter 21

22 The Ideal Process "The ideal chemical process is that which a one-armed operator can perform by pouring the reactants into a bath tub and collecting pure product from the drain hole" Sir John Cornforth (Nobel Prize 1975) 22

23 Catalysis & Green Chemistry Organocatalysis Biocatalysis Catalysis Homogeneous Heterogeneous Sheldon, Arends and Hanefeld, Green Chemistry And Catalysis, Wiley, New York,

24 The Solvent Problem : Catalysis in Non-conventional Reaction Media Two challenges : Toxicity and/or hazards of atmospheric and ground water pollution by conventional solvents Separation/recycling of homogeneous catalysts (Biphasic) catalysis in non-conventional media - water - supercritical carbon dioxide - ionic liquids The best solvent is no solvent 24

25 Solvent Selection Guide Pentane Hexane(s) Di-isopropyl ether Diethyl ether Dichloromethane Dichloroethane Chloroform NMP DMF Pyridine DMAc Dioxane Dimethoxyethane Benzene Carbon Tetrachloride Cyclohexane Toluene Methylcyclohexane TBME Isooctane Acetonitrile 2-MeTHF THF Xylenes DMSO Acetic Acid Ethylene Glycol Water scco 2 Acetone Ethanol 2-Propanol 1-Propanol Heptane Ethyl Acetate Isopropyl acetate Methanol MEK 1-Butanol t-butanol P. Dunn et al, Green Chem. 2008, 10,

26 Biocatalysis is Green & Sustainable Enzymes are derived from renewable resources and are biodegradable (even edible sometimes) Avoids use of (and product contamination by) scarce precious metals Mild conditions: ambient T & P in water High rates & highly specific : substrate, chemo-, regio-, and enantiospecific Higher quality product No special equipment needed Reduced environmental footprint 26

27 Historically: Adapt Process to fit Catalyst Available Catalyst Dream Process 27

28 Future: Adapt Catalyst to fit Ideal Process EVOLVE Catalyst Adapted Catalyst Nightmare Process Dream Process Compromise process to accommodate catalyst Directed Evolution Adapt catalyst to optimum process 28

29 The Challenge Disadvantages of Enzymes Low operational stability & shelf life Cumbersome recovery & re-use Product contamination Allergic reactions to proteins Non viable biocatalytic applications Costs are too high Not practical The Solution: Immobilization 29

30 Heterogeneous Catalysis with Enzymes Available Technologies Proprietary CLEA (Cross-Linked Enzyme Aggregate) Technology On various carriers Encapsulation Combinations 30

31 Conclusions & Take Home Message 1. There is not one winner. 2. There are Waste many chemo- Valorisation: and bio-catalytic methods 3. There are many shades of green. The New Frontier In an ideal chemical factory there is, strictly speaking, no waste but only products. The better a real factory makes use of its waste, the closer it gets to its ideal, the bigger is the profit. A. W. von Hofmann (1884) 31

32 Remediation Prevention Utilisation Valorisation Green Chemistry Sustainable Development 32

33 The Size of the Opportunity Lignocellulosic biomass residues: 220 X 10 9 tonnes /annum Rice husks: 120 X 10 6 tonnes / annum Sugar cane bagasse: 220 X 10 6 tonnes / annum Waste straw in China: 600 X 10 6 tonnes / annum Orange peel in Brazil: 8 X 10 6 tonnes / annum C. O. Tuck, E. Perez, I. T. Horvath, R. A. Sheldon, M Poliakoff, Science, 2012, 337,

34 The Valorisation Scale Product /ton Average Bulk Chemical 1000 Transportation Fuel Fermentation Feedstock Animal Feed Electricity Generation Landfill -/

35 Valorisation of glycerol ( 25.3 GJ/tonne) Product /GJ Epichlorohydrin Transport fuel 10 Electricity 3 35

36 Meaningful Metrics for Biomass Valorisation To measure is to know Lord Kelvin M eff = kgs product(s) kgs product(s)+ kgs waste E eff = energy out energy in Boundary conditions? (Cradle-Gate-Gate-Grave-Cradle) Land & Water Usage Economics A concise set of metrics for quick evaluation of petrochemical vs bio-based processes 36

37 Sustainability metrics of chemicals from biomass List of selected metrics: - material efficiency - total energy efficiency - land use - economic added value 37

38 Sustainability metrics of chemicals from biomass 38

39 Lignocellulosic biomass to sustainable fuels & chemicals The stone age didn t end when there were no more stones left 39

40 Production of Phloroglucinol by Fermentation Metabolically engineered E. coli 3.8 g/l in 12 h Not (yet) commercially viable Y.Cao, X. Jiang, R. Zhang & M. Xian, Appl Microbiol Biotechnol (2011) 91:

41 and Sustainable Thank you, any questions? 41