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 propertiesin the vicinity of, and especially just beyond, the critical data of pure carbon dioxide. The present chapterdescribes briefly the background and experimental details of four different methods. In the first case,scCO₂ is used as a “switch” to precipitate homogeneous catalystsand extract the organic components. Biphasic systems, where an immiscible liquid provides a permanentstationary phase for the catalyst, are exemplified for polyethylene glycol (PEG) and ionic liquids as thecatalyst phase. Finally, so-called inverted biphasic systems, where scCO₂ servesas the stationary phase for the catalyst, are presented with water as the mobile substrate/product phase.