Martyn Poliakoff

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UK-Canada Rutherford Lecture Multi-Phase
Catalysis in Supercritical Fluids

• Martyn Poliakoff

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HoraceBorton Keene(1886 1955)student with
RutherfordMy wifes grandfather
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Canadian PhD studentMorgan Thomasfrom Melfort
Saskatchewan Continuous reactions in
supercritical water
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Supercritical Fluids

• Gases e.g. CO2, C2H4, H2O compressed until they
  are nearly as dense as liquids
• SCFs can dissolve solids solubility increases
  with density (applied pressure)

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Critical Points
Pc
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Supercritical Catalysis

• Catalysis in scCO2- Hydrogenation,
  Hydroformylation
• Supercritical Water
• Biocatalysis

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Miscibility of H2/scCO2
Higher Concentration of Dissolved H2 in scCO2
Howdle, S. M., Healy, M. A., Poliakoff, M. J.
Am. Chem. Soc. 1990 112, 4804. Jessop, Ph. G.,
Ikariya, T., Noyori, R. Nature 1994, 368, 231.
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Continuous Supercritical Hydrogenation
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Other Hydrogenations successfullycarried out in
scCO2 and scPropane
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scCO2 Chemical Plant opened July,2002

• continuous
• multipurpose
• 1000 ton p.a.

Thomas Swan Co
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Hydrogenation of Isophorone
The product by-products have similar boiling
points Conventional process requires an
expensive downstream separation
scCO2 - quantitative, no by-products
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Continuous Hydroformylation
NJ Meehan, AJ Sandee, JNH Reek, PCJ Kamer PW van
Leeuwen, M Poliakoff Chem. Comm 2000, 1497
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scCO2 and Ionic Liquids
scCO2 very soluble in ILs ( 0.6 mole
fraction) ILs are insoluble in scCO2 L.A.
Blanchard, D. Hancu, E.J. Beckman and J.F.
Brennecke, Nature, 1999, 399, 28 scCO2 can
extract many organics from ILs L. A. Blanchard
and J. F. Brennecke, Ind. Eng. Chem. Res., 2001,
40, 287
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Bi-phasic Catalysis Cole-Hamilton
P. B. Webb, M. F. Sellin, et al. J. Am. Chem.
Soc.,2003, 125, 15577
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Green Chemistry 12 Principles
P R O D U C T I V E L Y
- 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
its safe
- 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
its safe
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Gas-Expanded Liquids
Increasing Pressure
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• CO2 is absorbed into the liquid phase and expands
  it
• Expansion directly related to the mole fraction
  CO2 in liquid phase

• a-pinene H2 CO2
• Ana Serbanovic at Universidade Nova de Lisboa

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Gas-Expanded liquids (GExLs)

• 1. Autoxidation by O2 in GExLs,
• DH Busch, B Subramaniam co-workers, Green
  Chem., 2004, 6, 387.
• 2. Enhanced Solubility of gases in GExLs,
• JF Brennecke coworkers, Ind. Eng. Chem. Res.,
  2006, 45, 5351.
• Gas Expanded Liquids,
• PG Jessop B Subramaniam,  Chem. Rev., 2007,
  107, 2666.

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Hydrogenation of Isophorone
Reaction has a high space-time yield How is this
influenced by the phase behaviour of the system?
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Isophorone /CO2/H2 phase boundaries
M. Sokolova Ke Jie
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CO2- expansion Hydrogenation

• Increases solubility of H2
• (B. Subramaniam, J. Brennecke)
• Increases diffusion ? faster transport across
  phase boundary (EJ Beckman)
• Reduces viscosity
• All of these accelerate reaction

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Continuous Hydrogenation in scCO2

• Works well BUT
• substrate product must be liquid or in solution
• by-products and any co-solvent require downstream
  separation
• product must be at least gt95 pure

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Continuous Hydrogenation in scCO2 The Next Step

• Hydrogenation of Levulinic acid
• Made from hexose containing material in the
  Biofine process

Rich Bourne, Jamie Stevens
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Levulinic Acid ? ?-Valerolactone

• GVL is a sustainable solvent / fuel additive
• (I.T. Horvath)
• Distillation to remove H2O is costly (GVL
  boiling point 207 C)

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Hydrogenation of LA in scCO2

• GVL is a liquid BUT
• Need a co-solvent to liquefy LA for pumping
• A recent patent uses 1,4-dioxane

US Pat. 2004254384, 2004
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Liquefying Levulinic Acid, mp 30oC
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LA ? GVL in scCO2
gt99 conversion 200oC, 100 bar
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THF H2O separation
Eckert et al., J. Phys. Chem. B, 2004, 108, 18108
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THF H2O separation
Eckert et al., J. Phys. Chem. B, 2004, 108, 18108
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Phase Behaviour GVL H2O CO2

• H2O THF are immiscible under CO2
• GVL behaves just like THF

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Combined System Reactor Separator
LA H2O
CO2
Catalyst
CO2
BPR
GVL
H2O
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Product Phases

• Bottom of separator
• H2O xs LA (identified by ATR FTIR)
• No GVL (by GC)
• Top of Separator
• NMR IR match to commercial GVL
• No other products or LA (by GC)
• Coulometric Karl Fischer lt0.4 H2O w/w

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Separation of product exploits phase behaviour
R Bourne, JD Stevens, J Ke, PA Hamley M.
Poliakoff, ChemComm on the web
Separation does not require extra energy
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Supercritical Catalysis

• Catalysis in scCO2
• Supercritical Water- Selective
  Oxidation, Formation of Caprolactam
• Biocatalysis

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Total Oxidation in scH2O

• Tc 374 oC pc 218 atm.
• At 300 oC, H2O is similar to acetone
• O2 is miscible with H2O above Tc
• Already has been used commercially

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Partial oxidation in scH2O?
Nottingham P.A. Hamley, E.G. Verdugo, J.
Fraga-Dubreuil, C. Yan, E. Venardou, R. Auerbach,
R.J. Pulham,T. Ilkenhans, M.J. Clarke, J.M.
Webster, M. Thomas, A. Johal, S. Joshi. INVISTA
Performance Technologies, UK W.B. Thomas,
G.R. Aird, I. Pearson, S.D. Housley, A.S. Coote,
K. Whiston, L.M. Dudd, J. Fraga-Dubreuil (ICI
D.A. Graham, P. Saxton)
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Oxidation of p-Xylene

• 0.7 Mton p.a. per plant
• TA insoluble in CH3COOH
• 18 of world production of CH3COOH lost in the
  process

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Continuous Oxidation of p-Xylene in scH2O?
TA
No organic solvents Homogeneous reaction
INVISTA Performance Technologies
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Oxidation of p-Xylene / scH2O
PA Hamley, et al. Green Chem. (2002) 4, 235
(2005) 7, 294
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Oxidation of p-Xylene in scH2O
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Selective Oxidation in scH2O

• If our results are scalable,
• total elimination of CH3COOH
• increased energy recovery compared to existing
  process
• significant reduction in cost of manufacturing TA

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EXAFS Molecular Dynamics Results with 0.4M MnBr2
W. Partenheimer, Y. Chen, J. L. Fulton J. Am.
Chem. Soc. 127, 14086, (2005)
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Raman Spectroscopy in scH2O
Eleni Venardou Appl. Spectrosc., (2003) 57
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Raman Spectra of CH3CN in ncH2O
no added acid 300 C, 300 bar
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Raman Spectra of CH3CN in ncH2O
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Hydrolysis of MeCN Effect of Concentration
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Caprolactam

• Industrial synthetic route
• Problem
• 5 kg (NH4)2SO4 are made per kg CPL

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Alternative Synthesis

• Cheaper feedstock,
• No cyclohexane oxidation
• No ammonium sulphate

Yan Chong
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Strategy
H. Vogel et al. Chem. Eng. Technol. (1999) 22,
494 70 conv. ACN but only 45 yield CPL 400
oC, 4 min. residence time

• Study effects of T and p
• Concentration of feedstock

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Caprolactam Summary

• Single-step green process

Hydrolysis, SCW
Cyclization, SCW
6-Aminocapronitrile, ACN
6-Aminocaproic acid amide, ACA
CPL

• gt60 yield of CPL within lt2 min
• No organic solvent
• No additional catalysts

C. Yan et al. WO2006078403 Green Chemistry in
the press
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Supercritical Catalysis

• Catalysis in scCO2
• Supercritical Water
• Multiphasic Biocatalysis
• Helen Hobbs, Neil Thomas

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Enzymes in Fluorous Biphase
PFMC Perfluoro- Methyl Cyclohexane
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How can one dissolve an enzyme in a fluorous
solvent (or even scCO2)?
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Hydrophobic Ion Pairing
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Fluorinated Anionic Surfactant
Krytox NH4 n 14/2500 KDP NH4 n 7/1400
Soluble in Fluorous phase and scCO2
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Cytochrome c inaqueous buffer
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Fluorous Phase added
Fluorous Krytox
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HIP extraction into theFluorous Phase
Butis the enzyme really dissolved?
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Dynamic Light Scattering Candida rugosa lipase
Expected Diameter 6.8 nm
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KDP surfactant mw1400 Expected length 1.4 nm
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Expected diameter 9.6 nm (CRL-KDP)
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Biocatalysis in Fluorous Biphase
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CMT-KDP Recycling (FBS)
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Dissolving Biomolecules

• Precipitation from aqueous buffer

Dissolve in scCO2
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Cytochrome C in scCO2
H. Hobbs et al. Angew. Chem. Intl Ed, (2007) 46,
7860 - 63
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Supercritical Catalysis

• Continuous Reactions
• Key aspect of supercritical fluids
• New Developments Green technologies are not in
  competition
• Partnership between Chemists Chemical Engineers

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• Impact
• Factor
• 4.19
• www.rsc.org/
• Greenchem

martyn.poliakoff_at_ nottingham.ac.uk
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P Licence NR Thomas PA Hamley
All our Students, Postdocs and Collaborators
P. Fields, R. Wilson, M. Guyler
INVISTA, Thomas Swan Co, GSK, ICI EPRSC, Royal
Society, EU Marie Curie
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Ernest Rutherford

• Cambridge Physics in the Thirties p 91
• He also held strongly to the opinion that
  research students should not be slaves to their
  work.
• For this reason the Cavendish closed at 6PM
• 11 of his students won Nobel prizes!