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选择性催化剂——除H2中微量CO催化剂,我逮住她了!!

已有 3355 次阅读 2007-11-7 13:01 |个人分类:催化科技导读



I capture the catalyst


06 November 2007

The largest transition metal-catalysed process in the chemical industry could soon get an efficiency boost, thanks to the isolation of a key catalytic intermediate.

UK chemists have made a new series of catalysts in an effort to up the efficiency of one of the most widely used, and energy-intensive, catalytic processes in the chemical industry - the conversion of carbon monoxide (CO) and methanol into acetic acid. Matthew Clarke and colleagues at St Andrews University, UK, have examined a series of diphosphine ligands in the rhodium-catalysed carbonylation of methanol. 'This is one of the simplest organic reactions there is, but because of the scale, it must be done so incredibly efficiently,' said Clarke.

The crystal structure of the rhodium catalyst

The industrial process used currently, BP's Cativa process, requires the starting CO to be purified, and the final product to be distilled - both of which are energy-expensive processes. Now BP is funding a project to look for the next generation of catalyst to get around either, or both, of these drawbacks.

Cheaper, lower grade CO includes large amounts of hydrogen, so to use it you need a catalyst that reacts with the CO but not the hydrogen, said Clarke. 'We identified a ligand, dppx [tetrakis(diphenylphosphino)-p-xylene], that was very selective,' he said. 'We isolated the catalytic intermediate, and showed it doesn't react with hydrogen, where the others do, so this is likely to be the origin of the selectivity.

"We're already making new catalysts based on this work, trying to gain a rational understanding of the selectivity"- Matthew Clarke, St Andrews University, UK
'We're already making new catalysts based on this work, trying to gain a rational understanding of the selectivity,' Clarke added. 'We haven't cracked it yet, but I have an inkling there is a ligand out there that is active, selective, stable and commercially viable.'

Andreas Danopoulos, who studies catalysis at the University of Southampton, UK, said the work was a good approach to understanding the catalyst. 'But I'm not sure that rational design is the best way to solve this problem - I think a combinatorial approach [to screen a large number of possible ligands] would be better,' he said.

James Mitchell Crow

Link to journal article

Evaluation of C4 diphosphine ligands in rhodium catalysed methanol carbonylation under a syngas atmosphere: synthesis, structure, stability and reactivity of rhodium(I) carbonyl and rhodium(III) acetyl intermediates
Gareth Lamb, Matthew Clarke, Alexandra M. Z. Slawin, Bruce Williams and Lesley Key, Dalton Trans., 2007
DOI: 10.1039/b712974b

Also of interest

New fluorophilic phosphines for use in catalysis

Advances in the synthesis of ligands for use in rhodium-based catalysts could lead to industrially viable applications.

Good catalysts require careful design

Designing a good catalyst is a delicate balance between steric and electronic properties, say researchers in Japan

Catalyst problems dissolve away

The products of an important industrial reaction have been found to dissolve the catalysts themselves, dispensing with the need for co-solvents.



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