Ionic Liquids and Carbon Dioxide as Combined Solvents for Reactions and Separations: The Miscibility Switch
Pp. 61-70 (10)
E. Kuhne, G. J. Witkamp and C. J. Peters
Ionic liquids (ILs) and carbon dioxide (CO2) are emerging as candidates to replace volatile organic
solvents in synthesis and extraction processes. ILs are a relatively new class of substances composed only of ions
and liquid at temperatures below 100oC. As a major attractive characteristic, they have negligible vapor pressure -
reducing solvent loss by evaporation and environmental pollution. When used simultaneously with carbon
dioxide for reactions and extractions, the process will be based on non-toxic, non-flammable solvents and will be
applicable for a wide variety of compounds. It has been recently shown that carbon dioxide can be used to split
phases in homogenous one-phase systems with ILs. This miscibility switch allows reactions to be carried out in
one phase, and by simply changing CO2 pressure, extractions can be carried out more efficiently under
heterogeneous conditions. This chapter presents an overview on ionic liquids and carbon dioxide, together with
an explanation on the phenomenon of miscibility switch.
Laboratory for Process Equipment, Delft University of Technology - Faculty of Mechanical, Maritime and Materials Engineering, The Netherlands.