| Abstract
| - Room-temperature ionic liquids (RTILs) provide an alternative for elimination of solvent emissions to theatmosphere for many reactions, but the subsequent separation of the products by conventional methods canbe a challenge. However, the use of supercritical carbon dioxide (scCO2) as an extractant offers potential fora novel class of environmentally benign media for chemical reaction and downstream separation. We haveinvestigated the solvent properties of mixtures of 1-butyl-3-methyl imidazolium hexafluorophosphate ([bmim][PF6]) and CO2 as functions of temperature (35−50 °C) and CO2 pressure (0−230 bar). We report the Kamlet−Taft dipolarity/polarizability parameter, volume expansion, and microviscosity. The results are consistentwith a picture of local enhancement of RTIL composition around a chromophore, maintaining solvent strengtheven at fairly high loadings of CO2, whereas the microviscosity in the vicinity of the solute is dramaticallyreduced, leading to enhanced mass transport and facilitated separation.
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