Grøn katalyse i superkritiske væsker
Martyn [email protected]
Green Chemistry (early 1990s) Cleaner approaches to
making chemicals & materials
Highlighted the need for “greener” solvents
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)
Critical Points
Pc
Tc
oC
HC3 8
H2O
35
65
95
360
390
CO2
CO2
C3H8
22
7.4
MPa
4.3H2O
Supercritical Catalysis
• Catalysis in scCO2:- Hydrogenation,
Photocatalysis
Miscibility of H2/SCF
T > TcT < Tc
Liquid
H2
High Concentration of H2 in SCF Concentration is independent of T
SM Howdle, M Poliakoff, ISSF, Nice 1988
SCF+H2
Continuous Supercritical Hydrogenation
scCO2
CO2Product
Reactant + H2
Catalyst
Reactor
Lab Reactor
Hydrogenation of IsophoroneO
Pd Deloxan®
100 bar, scCO240-170°C
+ H2
O
scCO2 - 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.
scCO2
ChemicalPlant
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
PRODUCTIVELY
- 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 scCO2
O OH O
OO
Acid/Base
Acid/Base-H2O
H2, Pd
JG StevensRA Bourne
Green Chem., 11 (2009) 409
Gas-Expanded Liquids
Increasing Pressure
LiquidLiquid+CO2
Liquid+CO2
• Mixture of Mixture of αα-pinene -pinene and COand CO22
• Courtesy of Anna Courtesy of Anna Milewska at Milewska at Universidade Nova Universidade Nova de Lisboade Lisboa
70 bar70 bar
• Mixture of Mixture of αα-pinene -pinene and COand CO22
• Courtesy of Anna Courtesy of Anna Milewska at Milewska at Universidade Nova Universidade Nova de Lisboade Lisboa
85 bar85 bar
• Mixture of Mixture of αα-pinene -pinene and COand CO22
• Courtesy of Anna Courtesy of Anna Milewska at Milewska at Universidade Nova Universidade Nova de Lisboade Lisboa
94 bar94 bar
• Mixture of Mixture of αα-pinene -pinene and COand CO22
• Courtesy of Anna Courtesy of Anna Milewska at Milewska at Universidade Nova Universidade Nova de Lisboade Lisboa
97 bar97 bar
• Mixture of Mixture of αα-pinene -pinene and COand CO22
• Courtesy of Anna Courtesy of Anna Milewska at Milewska at Universidade Nova Universidade Nova de Lisboade Lisboa
99 bar99 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 CO2 & Other Gases” GR Akien and M Poliakoff,
Green Chem., 2009, 11, 1083
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 compared to conventional
solvents
Continuous Hydrogenation in scCO2
Works well BUT
• substrate & product must be liquid
• by-products require downstream separation
• product must be at least >95% pure
Continuous Hydrogenation in scCO2: The Next Step
• Hydrogenation of Levulinic acid
• Made from hexose containing material in the Biofine process
OH
O
O
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 H2O is costly (GVL: boiling point 207 °C)
OH
O
O O
O+ H2
-H2O
LA GVL
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
Levulinic Acid
H2O
Levulinic Acid
Levulinic Acid +
H2OH2O
• H2O is by-product of reaction
• Greener than toluene or 1,4 dioxane
• But does the hydrogenation still work in H2O ???
H2O as a co-solvent in scCO2?
This Work Patent
Catalyst 5% Ru/SiO2 5% Ru/Al2O3
CO2:LA 10 : 1 28 : 1
H2:LA 3 : 1 1.1 : 1
Pressure 100 bar 200 bar
Solvent System
scCO2 + H2O scCO2 +1,4-dioxane
Yield >99% >99%
LA GVL in scCO2
CO2 + xsH2
GVL + H2O + xsLA
LA + H2O
Ru/SiO2
CO2
H2
THF + H2O separation
THF/H2O + Dye
Eckert et al., J. Phys. Chem. B, 2004, 108, 18108
THF + H2O separation
THF/H2O + Dye
H2O + Dye
THF + CO2
Eckert et al., J. Phys. Chem. B, 2004, 108, 18108
H2O & THF are immiscible under CO2
Does GVL behave like THF???
Phase Behaviour GVL + H2O + CO2
OOO
THF GVL
1 bar, 20.2°C.
GVL + H2O + Direct Red 23
GVL+CO2
CO2
H2O
93 bar43.7 °C
Hydrogenation of LA to GVL
CO2
GVL
LA + H2O
Catalyst
CO2
H2
xsLA + H2O
R Bourne, JD Stevens,
J Ke,
M. Poliakoff, ChemComm 2007, 4632-4
Separation does not require extra energy
Catalysis in scCO2
• Catalytic hydrogenation of Furfural
Jamie Stevens, Rich Bourne
Furfural Hydrogenation Routes
Conventional processes use
Copper Chromite catalyst
OCHO
O
-CO
OCH2OH
OCH2OH
OCHO
OCH3
O
OCH3
H2
H2H2
H2
H2
H2
250 °C
H2
Automated Continuous Reactions
High pressure Sample Loop
Product
Reactants
Catalyst
CO2
GC Analysi
s
CO2
T, p, Flow Rate (organic + scCO2) can all be programmed
Copper Chromite Catalyst0.05 mL/min furfural, 1.0 mL/min CO2,
150 bar, 2 equivalents H2
50 100 150 200 250
0
20
40
60
80
100
Per
centa
ge
com
posi
tion
Temp /°C
30 X Scale
10 Y Scale
OOH
O Me
OO
oC
30% Cu on silica (no Cr!)
0.05 mL/min furfural, 1.0 mL/min CO2, 150 bar, 2 equivalents H2
50 100 150 200 250
0
20
40
60
80
100
Per
centa
ge
Com
posi
tion
Temp /°C
OOH
O Me
OO
oC
Hydrogenation of Furfural
• Chromium can be eliminated
• Cu/SiO2 gives high selectivity for furfuryl alcohol
• Reaction works better in the presence of CO2
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
EtOHEt2O + H2O
C2H4 + H2Osolid acid
Andy Parrott, Rich Bourne
Et2O
Supercritical Catalysis
• Catalysis in scCO2:- Hydrogenation, Photocatalytic oxidation
In collaboration with Mike George
Günther Otto Schenck (Heidelberg, ca. 1947)
Can we carry out the reaction in
scCO2?
Photo -catalysis
O2
hv
O
O
α -Terpinene Ascaridole
RA Bourne, X Han, A Chapman,
N Arrowsmith, H Kawanami
O2
hv
O
O
α -Terpinene Ascaridole
N
NH N
HN
FF
F
FF
F
F
FF
F
F F
F F
F
F
F F
F
F
CO2 solublePhotosensitiser
TPFPP
Photooxidation 1O2 in scCO2
Why scCO2?
Miscible with gaseous O2
Non-flammable
Easy product separation
0
1
2
302030303040305030603070308030903100
wavenumber/cm-1
Ab
sorb
ance
0
Series2
FTIR Monitoring
140bar; 40°C; 1.31 mol % O2 in scCO2
0
1
2
302030303040305030603070308030903100
wavenumber/cm-1
Ab
so
rba
nc
e
0
200s
O
O
0
1
2
302030303040305030603070308030903100
wavenumber/cm-1
Ab
sorb
ance
0
20s
40s
60s
80s
100s
120s
140s
160s
180s
200s
O
O
Kinetics
0
0.4
0.8
1.2
1.6
2
0 50 100 150 200
time/s
Ab
sorb
ance 3060 cm-1
3042 cm-1
Photocatalysis in scCO2
O2
hv
O
O
α -Terpinene Ascaridol
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, 4457.
Batch Reactor:
30 μL product
Continuous Flow with 1O2
• CO2 Flow 1.0 mL/min
• Org. Flow 0.2 mL/min
• 2 Equivalents of O2
• 8 LEDs
• Tube Reactor
Sapphire tube
Continuous
1O2 Reactions:x 3000 Scale Up
100 % yield; 0.2 g/min
30 μL
96 mL
Extension of Concept:Synthesis of Rose Oxide
OH OH OH
OOH
O
OH
+
OH OH
OH
HO
+O
O2scCO2
DMCTPFPPhv
Na2SO3-H2O-Na2SO4
HCl
-H2O
1O2 Space Time Yields:conventional vs scCO2
Conventional solventsSchenk Reactor 0.1 mmol L-1min-1
Micro-reactor 0.9 mmol L-1min-1
scCO2 system 70 mmol L-1min-1
RA Bourne, X Han, M Poliakoff, MW George, Angew. Chem. Int. Ed., 2009, 48, 5322
CO2 and Carbon Capture
2000 tons CO2 per hour
Thomas Swan plant<1 ton CO2 per hour!!
Mike GeorgeTrevor 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, AstraZenecaEPRSC, Royal Society, EU Marie Curie
All our Students,Postdocs and Collaborators
Mike GeorgeRich Bourne
IT Horvath
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