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 K 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.