Catalyst Immobilization using SCFs as the Only Mass-Separating Agent

Catalyst Immobilization using SCFs as the Only Mass-Separating Agent 

Copyright 2005 Wiley-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 3-527-30721-4 

This systematic classification of recycling methods can be related directly to the solubility properties of the organometallic catalysts. The majority of these are poorly soluble in CO2, which therefore acts as an anti-solvent for solutions containing such species. However, either substrates or products may act as entrainers which serve to enhance the CO2 solubility, so in some cases additional catalyst modification may be necessary to render them sufficiently C02-phobic for efficient separation. In the other two approaches, the catalysts need to be C02-philic to ensure sufficient solubility in the C02-based media under the reaction conditions. This behavior is exhibited by certain volatile and nonpolar complexes such as transition metal carbonyl complexes, and also by metal complexes containing suitably modified ligands (e.g., containing perfluoroalkyl groups). 

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