Grøn katalyse i superkritiske væsker

Martyn Poliakoffmartyn.poliakoff@nottingham.ac.uk

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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www.rsc.org/GreenChem

martyn.poliakoff@nottingham.ac.uk

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