(450i) Modeling the Solubility of Gases in Ionic Liquids with the Soft-Saft Equation

Room temperature ionic liquids (ILs) are currently receiving much attention due to their interesting physico-chemical properties: negligible vapor pressure, extremely wide range of compositions (which allows the tuning of physical properties through design), etc. For these reasons, ILs are being postulated as promising alternative solvents for a number of technological applications in the context of green processes. A careful characterization of them is needed prior they are put into final use for a specific application; this includes knowledge of the relationship between the structure and the properties. This knowledge can be obtained by experimental techniques, simulations and/or theoretical approaches. A main advantage of a theory or equation of state versus the other techniques is the speed in which these calculations are performed, provided they are accurate enough to reproduce the experimental data. We present here the successful application of the soft-SAFT equation of state to predict the solubility of gases in selected families of ionic liquids. The equation has been first applied to the pure ILs, obtaining molecular parameters which correlate with the molecular weight of the IL. The solubility of CO2 and other gases in these ionic liquids, at low and high pressures, is predicted with high accuracy by the equation. The molecular nature of the equation is used to check the influence of the chain length and the anion on the solubility of these gases at the same thermodynamic conditions.

This work is partially financed from the Spanish Government (CTQ2005-00296/PPQ) and by the Generalitat de Catalunya (2005SGR-00288). Additional support from Air Products through a MATGAS project grant is also acknowledged.