Martyn Poliakoff

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Catalisi a fasi multiple Massimizzando le
opportunità per i fluidi supercritici nella
chimica verde

• Martyn Poliakoff
• martyn.poliakoff_at_nottingham.ac.uk

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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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Green Chemistry (early 1990s)
Cleaner approaches to making chemicals
materials
Highlighted the need for greener solvents
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Decaffeinationin scCO2

• A great example of a Green Process
• Highlighted scCO2 as a Green Solvent

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Supercritical Catalysis

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

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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 in commercial use for total oxidation

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Selective 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, E.V.
Perez INVISTA Performance Technologies, UK
W.B. Thomas, G.R. Aird, I. Pearson, S.D. Housley,
A.S. Coote, K. Whiston, L.M. Dudd (ICI D.A.
Graham, P. Saxton)
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Oxidation of p-Xylene

• 0.5 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 (2007) 9,1238
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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 0.4 m
MnBr2
W. Partenheimer, Y. Chen, J. L. Fulton J. Am.
Chem. Soc. 127, 14086, (2005)
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Holey Fibres Phase Behaviour
AA Novitskii EV Perez, WZ Wu
20 µ
20 µ
H2O EtOH
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Raman Spectroscopy
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

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

Yan C, et al. Green Chem. 10 (2008) 98
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Supercritical Catalysis

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

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Miscibility of H2/scXe
scXe H2
High Concentration of H2 in scXe Concentration
is independent of T SM Howdle, M Poliakoff, ISSF,
Nice 1988
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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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Hydrogenation of a-pinene A. Serbanovic, V.
Najdanovic-Visak, A. Paiva, G. Brunner, M.
Nunes da Ponte 8th ISSF, Kyoto
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Gas-Expanded liquids (GExLs)

• 1. Autoxidation by O2 in GExLs,
• DH Busch, B Subramaniam coworkers, Green
  Chem., 2004, 6, 387.
• 2. Enhanced Solubility of gases in GExLs,
• JF Brennecke coworkers, Ind. Eng. Chem. Res.,
  2006, 45, 5351.
• CO2-Protected Amine Formation in GExLs
• X. Xie, C. L. Liotta C. A. Eckert, Ind. Eng.
  Chem. Res., 2004, 43, 7907.

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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
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CO2-expansion Hydrogenation

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

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Continuous Hydrogenation in scCO2

• Works well BUT
• substrate product must be liquid
• by-products 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
• 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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H2O as a co-solvent in scCO2?

• H2O is by-product of reaction
• Greener than toluene or 1,4 dioxane
• But does the hydrogenation still work in H2O ???

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This Work Patent
Catalyst 5 Ru/SiO2 5 Ru/Al2O3
CO2LA 10 1 28 1
H2LA 3 1 1.1 1
Pressure 100 bar 200 bar
Solvent System scCO2 H2O scCO2 1,4-dioxane
Yield gt99 gt99
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LA ? GVL in scCO2
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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
• Does GVL behave like THF???

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1 bar, 20.2C.
GVL H2O Direct Red 23
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CO2
93 bar 43.7 C
GVLCO2
H2O
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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 Pure GVL !!!
• 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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Hydrogenation of LA to GVL
R Bourne, JD Stevens, J Ke, M. Poliakoff,
ChemComm 2007, 4632-4
Separation does not require extra energy
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Photochemistry
Thanks to M. Oelgemöller, Dublin
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Photo -catalysis
Can we carry out the reaction in scCO2?
MW George, RA Bourne, X. Han A Chapman
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Photooxidation 1O2 in scCO2
Why scCO2?
CO2 soluble Photosensitiser TFPTPP
Non-flammable
Easy product separation
Miscible with gaseous O2
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Batch Reactor for 1O2withphoto-diode
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FTIR Monitoring
140bar 40C 1.31 mol O2 in scCO2
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Kinetics
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Comparison with CCl4
Photo- sensitizer Solvent System O2 (mol) Substrate PS (mol mol) TOF (s-1)
TFPTPP 140 bar CO2 1.31 748 12
TFPTPP 140 bar CO2 2.63 748 11
TFPTPP 140 bar CO2 3.93 748 11
TFPTPP CCl4 2.6 bar 1497 7
TPP CCl4 2.1 bar 1497 3
Reaction is faster in scCO2
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Continuous Flow with 1O2
out

• CO2 Flow 1.0 mL/min
• Org. Flow 0.2 mL/min
• 2 Equivalents of O2
• 8 LEDs
• Sapphire Tube Reactor

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Photocatalysis in scCO2
scCO2 potentially better than CCl4 R. A. Bourne,
X. Han, A. O. Chapman, N. Arrowsmith, H.
Kawanami, M. Poliakoff, M. W. George, Chem. Comm.
2008, in the press.
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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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DICE Driving Innovation in Chemistry
Engineering

• 4.4 M UK initiative led by Nottingham to
  stimulate research at the Chem/Chem.Eng interface
• 5 new faculty members
• Big opportunities for collaboration
• www.nottingham.ac.uk/DICE

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Mike George Pete Licence AA Novitskiy
All our Students, Postdocs and Collaborators
P. Fields, R. Wilson, M. Guyler
INVISTA, Thomas Swan Co, AstraZeneca EPRSC,
Royal Society, EU Marie Curie
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www.periodicvideos.com
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• Impact
• Factor
• 4.836
• www.rsc.org/
• GreenChem

martyn.poliakoff_at_ nottingham.ac.uk