Grøn katalyse i superkritiske væsker Martyn Poliakoff

Green Chemistry (early 1990s) Cleaner approaches to making chemicals & materials Highlighted the need for “greener” solvents

Supercritical Fluids Gases e.g. CO 2, C 2 H 4, H 2 O compressed until they are nearly as dense as liquids SCFs can dissolve solids solubility increases with density (applied pressure)

Critical Points PcPc TcTc o C HC 38 H2OH2O CO 2 2 C 3 H MPa 4.3 H2OH2O

Supercritical Catalysis Catalysis in scCO 2 :- Hydrogenation, Photocatalysis

Miscibility of H 2 /SCF T > T c T < T c Liquid H 2 High Concentration of H 2 in SCF Concentration is independent of T SM Howdle, M Poliakoff, ISSF, Nice 1988 SCF +H 2

Continuous Supercritical Hydrogenation scCO 2 CO 2 Product Reactant + H 2 Catalyst

Reactor Lab Reactor

Hydrogenation of Isophorone O Pd Deloxan® 100 bar, scCO °C + H 2 O scCO 2 - quantitative, no by-products The product & by-products have similar boiling points Conventional process requires an expensive downstream separation

continuous multipurpose 1000 ton p.a. scCO 2 Chemical Plant opened July,2002 Thomas Swan & Co

Green Chemistry 12 Principles - Prevent wastes - Renewable materials - Omit derivatization steps - Degradable chemical products - Use safe synthetic methods - Catalytic reagents - Temperature, Pressure ambient - In-Process Monitoring - Very few auxiliary substances - E-factor, maximize feed in product - Low toxicity of chemical products - Yes it’s safe PRODUCTIVELYPRODUCTIVELY - Prevent wastes - Renewable materials - Omit derivatization steps - Degradable chemical products - Use safe synthetic methods - Catalytic reagents - Temperature, Pressure ambient - In-Process Monitoring - Very few auxiliary substances - E-factor, maximize feed in product - Low toxicity of chemical products - Yes it’s safe

Tandem Reactions in scCO 2 JG Stevens RA Bourne Green Chem., 11 (2009) 409

Gas-Expanded Liquids Increasing Pressure Liquid +CO 2 Liquid +CO 2

Mixture of α-pinene and CO 2Mixture of α-pinene and CO 2 Courtesy of Anna Milewska at Universidade Nova de LisboaCourtesy of Anna Milewska at Universidade Nova de Lisboa 70 bar

Mixture of α-pinene and CO 2Mixture of α-pinene and CO 2 Courtesy of Anna Milewska at Universidade Nova de LisboaCourtesy of Anna Milewska at Universidade Nova de Lisboa 85 bar

Mixture of α-pinene and CO 2Mixture of α-pinene and CO 2 Courtesy of Anna Milewska at Universidade Nova de LisboaCourtesy of Anna Milewska at Universidade Nova de Lisboa 94 bar

Mixture of α-pinene and CO 2Mixture of α-pinene and CO 2 Courtesy of Anna Milewska at Universidade Nova de LisboaCourtesy of Anna Milewska at Universidade Nova de Lisboa 97 bar

Mixture of α-pinene and CO 2Mixture of α-pinene and CO 2 Courtesy of Anna Milewska at Universidade Nova de LisboaCourtesy of Anna Milewska at Universidade Nova de Lisboa 99 bar

Gas-Expanded liquids (GExLs) “Gas-Expanded Liquids” PG Jessop, B Subramaniam, Chem. Rev., 2007, 107, 2666 “A Critical Look at Reactions in Class I and II Gas-Expanded Liquids using CO 2 & Other Gases” GR Akien and M Poliakoff, Green Chem., 2009, 11, 1083

CO 2 -expansion & Hydrogenation Increases solubility of H 2 (B. Subramaniam, J. Brennecke) Increases diffusion  faster transport across phase boundary (EJ Beckman) Reduces viscosity All of these accelerate reaction compared to conventional solvents

Continuous Hydrogenation in scCO 2 Works well BUT substrate & product must be liquid by-products require downstream separation product must be at least >95% pure

Continuous Hydrogenation in scCO 2 : The Next Step Hydrogenation of Levulinic acid Made from hexose containing material in the Biofine process Rich Bourne, Jamie Stevens

Levulinic Acid  γ-Valerolactone GVL is a sustainable solvent / fuel additive I.T. Horvath, Green Chem. 10 (2008) 238 Distillation to remove H 2 O is costly (GVL: boiling point 207 °C) LAGVL

Hydrogenation of LA in scCO 2 GVL is a liquid BUT Need a co-solvent to liquefy LA for pumping A recent patent uses 1,4-dioxane US Pat , 2004

Levulinic Acid H2OH2O

Levulinic Acid + H 2 O H2OH2O

H 2 O is by-product of reaction Greener than toluene or 1,4 dioxane But does the hydrogenation still work in H 2 O ??? H 2 O as a co-solvent in scCO 2 ?

This WorkPatent Catalyst5% Ru/SiO 2 5% Ru/Al 2 O 3 CO 2 :LA 10 : 128 : 1 H 2 :LA3 : 11.1 : 1 Pressure 100 bar200 bar Solvent System scCO 2 + H 2 OscCO 2 + 1,4-dioxane Yield>99%

LA  GVL in scCO 2 CO 2 + xsH 2 GVL + H 2 O + xsLA LA + H 2 O Ru/SiO 2 CO 2 H2H2

THF + H 2 O separation THF/H 2 O + Dye Eckert et al., J. Phys. Chem. B, 2004, 108, 18108

THF + H 2 O separation THF/H 2 O + Dye H 2 O + Dye THF + CO 2 Eckert et al., J. Phys. Chem. B, 2004, 108, 18108

H 2 O & THF are immiscible under CO 2 Does GVL behave like THF??? Phase Behaviour GVL + H 2 O + CO 2 THFGVL

1 bar, 20.2°C. GVL + H 2 O + Direct Red 23

GVL+CO 2 CO 2 H2OH2O 93 bar 43.7 °C

Hydrogenation of LA to GVL CO 2 GVL LA + H 2 O Catalyst CO 2 H2H2 xsLA + H 2 O R Bourne, JD Stevens, J Ke, M. Poliakoff, ChemComm 2007, Separation does not require extra energy

Catalysis in scCO 2 Catalytic hydrogenation of Furfural Jamie Stevens, Rich Bourne

Furfural Hydrogenation Routes Conventional processes use Copper Chromite catalyst

Automated Continuous Reactions High pressure Sample Loop Product Reactants Catalyst CO 2 GC Analysis CO 2 T, p, Flow Rate (organic + scCO 2 ) can all be programmed

Copper Chromite Catalyst 0.05 mL/min furfural, 1.0 mL/min CO 2, 150 bar, 2 equivalents H 2 oCoC

30% Cu on silica (no Cr!) 0.05 mL/min furfural, 1.0 mL/min CO 2, 150 bar, 2 equivalents H 2 oCoC

Hydrogenation of Furfural Chromium can be eliminated Cu/SiO 2 gives high selectivity for furfuryl alcohol Reaction works better in the presence of CO 2

Self-Optimizing Reactions? Specify desired product of the reaction Use on-line GC analysis to vary parameters (e.g. T) to maximize yield Preliminary studies encouraging EtOH Et 2 O + H 2 O C 2 H 4 + H 2 O solid acid Andy Parrott, Rich Bourne

Et 2 O

Supercritical Catalysis Catalysis in scCO 2 :- Hydrogenation, Photocatalytic oxidation In collaboration with Mike George

Günther Otto Schenck (Heidelberg, ca. 1947) Can we carry out the reaction in scCO 2 ? Photo - catalysis α -TerpineneAscaridole RA Bourne, X Han, A Chapman, N Arrowsmith, H Kawanami

α -TerpineneAscaridole CO 2 soluble Photosensitiser TPFPP Photooxidation 1 O 2 in scCO 2 Why scCO 2 ? Miscible with gaseous O 2 Non-flammable Easy product separation

FTIR Monitoring 140bar; 40°C; 1.31 mol % O 2 in scCO 2

Kinetics time/s Absorbance 3060 cm cm -1

Photocatalysis in scCO 2 α -TerpineneAscaridol scCO 2 potentially better than CCl 4 R. A. Bourne, X. Han, A. O. Chapman, N. Arrowsmith, H. Kawanami, M. Poliakoff, M. W. George *, Chem. Comm. 2008, 4457.

Batch Reactor: 30 μL product

Continuous Flow with 1 O 2 CO 2 Flow 1.0 mL/min Org. Flow 0.2 mL/min 2 Equivalents of O 2 8 LEDs Tube Reactor Sapphire tube

Continuous 1 O 2 Reactions: x 3000 Scale Up 100 % yield; 0.2 g/min 30 μL 96 mL

Extension of Concept: Synthesis of Rose Oxide

1 O 2 Space Time Yields: conventional vs scCO 2 Conventional solvents Schenk Reactor0.1 mmol L -1 min -1 Micro-reactor 0.9 mmol L -1 min -1 scCO 2 system 70 mmol L -1 min -1 RA Bourne, X Han, M Poliakoff, MW George, Angew. Chem. Int. Ed., 2009, 48, 5322

CO 2 and Carbon Capture 2000 tons CO 2 per hour Thomas Swan plant <1 ton CO 2 per hour!! Mike George Trevor Drage

Supercritical Catalysis Continuous Reactions: Key aspect of supercritical fluids New Developments: “Green” technologies are not in competition Partnership between Chemists & Chemical Engineers

P. Fields, R. Wilson, M. Guyler INVISTA, Thomas Swan & Co, AstraZeneca EPRSC, Royal Society, EU Marie Curie All our Students, Postdocs and Collaborators Mike George Rich Bourne IT Horvath

Impact Factor GreenChem nottingham.ac.uk

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