Extension of the UNIFAC Model for Ionic Liquids

The UNIFAC model has recently become very popular for ionic liquids (ILs) because of its applicability for prediction of thermodynamic properties. This work is a continuation of our studies on the extension of group parameters of the UNIFAC model to systems with ILs. The new IL groups for 33 main groups and 53 subgroups were added into the current UNIFAC parameter matrix. The parameters of group surface area and volume for ILs were obtained by the COSMO calculation, while the group binary interaction parameters, a(nm) and a(mn), were obtained by means of correlating the activity coefficients of solutes at infinite dilution in ILs at different temperatures exhaustively collected from literature by the end of 2011. The predicted results of UNIFAC model are more accurate than those of the COSMO-RS model so that it can be used for identifying the general relationship between molecular structure of ILs and separation performance for the separation of liquid mixtures with ILs.