This paper shows how gas solubility can be predicted in Rmim-based room-temperature ionic liquids (RTILs).We have developed a model to illustrate that ideal, single-gas solubility in Rmim-based RTILs is primarily a function of molar volume of the RTIL. This method is used to estimate bulk-fluid gas solubility, showing that for Rmim-based RTILs there is a particular molar volume where a maximum amount of gas per volume of RTIL occurs at a given pressure and temperature. This method is also used to estimate gas permeability and gas pair separation selectivity for ideal CO 2 /N 2 and CO 2 /CH 4 separations. A comparison to traditional polymer membranes utilized in these separations is included in the form of a "Robeson plot".

The ability to predict the solubility of gases in room-temperature ionic liquids, RTILs, would be very useful in determining the most efficient RTIL to use in an industrial process. This work uses data from CO 2 and C 2 H 4 solubility measurements to show that regular solution theory can be used to model gas solubilities in RTILs at low pressures. This work further discusses how changes in pressure and temperature affect the solubility of gases in RTILs.

This paper explores the arguments for using solubility parameters and the regular solution theory for modeling gas solubilities in five different room-temperature ionic liquids (RTILs) at low partial pressures (<1 atm) and low mole fractions (<0.1). The experimentally measured and reported carbon dioxide (CO2) solubilities at low mole fractions (<0.05) suggest positive deviations from Raoult's law for CO2/RTIL solutions. These CO2 solubility deviations from Raoult's law indicate that CO2/RTIL complexations are not the sole controlling factor in relative CO2 solubilities. The RTILs' energies of vaporization and molar volumes appear to be factors in determining relative CO2 solubilities between RTILs. The energies of vaporization for the RTILs were empirically estimated from their melting points.