CO 2 Transport UKCCSC Progress Report Newcastle University P.N. Seevam, J.M.Race, M.J.Downie,
UKCCSC Meeting, 18 - 19 April 2007 Nottingham
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Transcript of UKCCSC Meeting, 18 - 19 April 2007 Nottingham
UKCCSC Meeting, 18 - 19 April 2007 Nottingham
Long Term Utilisation
To develop, for the first time, catalysts which allow photocatalytic reduction to be performed in supercritical CO2
Prof M. George / A. Cowan
Strategy for CO2 Reduction
• Reduction of CO2 requires energy
Photon as energy source (Photochem)
Electricity as energy source (Electrochem)
• One electron process is unfavorable
Multi-electron transfer catalysts
CO2 + e- CO2- E = 1.9 V (vs NHE at pH 7)
CO2 + H+ + 2e- HCO2- E = 0.49 V
CO2 + 2H+ + 2e- CO + H2O E = 0.53 V
CO2 + 6H+ + 6e- CH3OH + H2O E = 0.38 VComments Inorg. Chem. 1997, 19, 67Coord. Chem. Rev. 1999, 185, 373
CO2 ReductionIf Nature Can Do It,
Why Can't We?
http://photoscience.la.asu.edu
• Artificial photosynthesis for CO2 reduction typically requires a
photosensitizer, a catalyst and an electron donor
• Products are CO, formate, and H2
Charge separation
Re
N
NCl
CO
CO
CO
Re
N
NCl
CO
CO
CO
+-
Re
N
NCl
CO
CO
CO
-
charge separationh
TEA
TEA+
• Co macrocycles
• Ni macrocycles
• Cobalt and Iron porphyrins,
Phthalocyanines and corroles
• Ru(bpy)2(CO)X
• Re(bpy)(CO)3X
• Ni(bpy)32+
Re
N
NCl
CO
CO
CO
- CO, formate, carbonate are produced
- BUT: low turnover numbers, catalyst poisoning, by-products
George, M. W., et al. (1996) Organometallics 15, 3374-3387
• Reaction of the catalytically active species with CO2 is very slow
• Solvent binds to the “vacant site”
-Low turnover numbers, catalyst poisoning, by-products
Hayashi, Y., Kita, S., Brunschwig, B. S. & Fujita, E. (2003) J. Am. Chem. Soc., 125, 11976-11987.
•CO2 is the solvent and reagent
•Achieve solvent density comparable to conventional solvents
•Tuneable Properties
Why operate in scCO2 ?
Tc = 304 K
Pc= 72.9 atm
• Problem: Most metal carbonyls are insoluble in non-polar solvents!
• Solution:
C9H19 chains
Soluble in non-polar solvents!
N
N
Re
ClOC
OC
OC
Re
N
NCl
CO
CO
CO
Re
N
NCl
CO
CO
CO
Re
N
NCl
CO
CO
CO
8
8
• Investigate photophysics/photochemistry in conventional solvents and scCO2
• Test catalytic ability of new complexes in scCO2
• Feedback into rational catalyst design
PROBE SAMPLE DETECTOR
PUMP
IR
UV
TRIR Spectroscopy
Kinetic studies of mechanisms from picosecond (10-12 s) to seconds
2100 2050 2000 1950 1900 1850
OD = 0.052052
2022
1977
1951
1925
1906
50 ns
Re
N
NCl
CO
CO
CO
X
X
Re
N
NCl
CO
CO
CO
+-
X
X
charge separation
h
In n-heptane similar excited state to un-substituted complex
v
Conclusions• Solvent coordination is a problem in existing
Re-bpy CO2 reduction catalysts
• CO2 soluble analogue may overcome this problem – work in scCO2
• Currently examining mechanism with TRIR spectroscopy
• We will start testing catalytic ability shortly
• Mike George
• Etsuko Fujita / Dave Grills
• John Gavey
Future aims
• A fundamental challenge is the replacement of the “sacrificial” electron donors by species that will lead to useful (or benign) chemicals in their own right
– CO2 + 2H2O CH3OH + O2
– CO2 + CH4 CH3COOH
• If we can do this, then we can do what Nature does