Predicting the Solubility of CO2 in Toluene + Ionic Liquid Mixtures with PC-SAFT

Abstract

Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was applied for modeling the vapor-liquid equilibrium of CO2 + toluene + ionic liquid (IL) mixtures and the molar volume of their liquid phases at temperatures between 298.15 and 333.15 K and at pressures up to 80 bar. ILs used for this study contain the bis(trifluoromethylsulfonylimide) anion ([Tf2N]-) and imidazolium, pyridinium, thiolanium and phosphonium cations. The pure-IL PC-SAFT parameters were fit to pure-IL liquid density data. Temperature dependent binary interaction parameters were fit to binary liquid-liquid equilibrium data (i.e. toluene + IL) obtained from the literature and some points measured for this work. Temperature independent binary interaction parameters were fit to vapor-liquid equilibrium data (CO2 + IL, CO2 + toluene) from the literature. The availability of the pure-IL parameters and binary interaction parameters allowed prediction of CO2 solubility in toluene + IL mixtures with an absolute average relative deviation (AARD) of 6.8 %, as well as molar volumes of CO2 + toluene + IL mixtures with an AARD of 5.0 %, for the four ternary systems under investigation.