Regulated systems for catalyst immobilisation based on supercritical carbon dioxide

Abstract

Promising strategies to use supercritical CO2 (scCO2) for catalyst immobilisation can be developed on the basis of its unique and tunable solubility properties in the vicinity of, and especially just beyond, the critical data of pure carbon dioxide. The present chapter describes briefly the background and experimental details of four different methods. In the first case, scCO2 is used as a "switch" to precipitate homogeneous catalysts and extract the organic components. Biphasic systems, where an immiscible liquid provides a permanent stationary phase for the catalyst, are exemplified for polyethylene glycol (PEG) and ionic liquids as the catalyst phase. Finally, so-called inverted biphasic systems, where scCO2 serves as the stationary phase for the catalyst, are presented with water as the mobile substrate/product phase. © 2008 Springer-Verlag Berlin Heidelberg.