Thermodynamic Modeling of Solubility of Acid Gases and Sulfur Compounds in Ionic Liquids Using Electrolyte PC–SAFT Equation of State

The electrolyte perturbed chain statistical associating fluid theory (ePC–SAFT) equation of state (EOS) was used to model the solubility of acid gases in ionic liquids (ILs). The studied gases include COS, CS2, CH3SH, CO2 and H2S. Four imidazolium-based ILs with the anion (trifluoromethylsulfonyl)imide are studied, which formula can be written as [Cnmim][Tf2N], where n = 2, 4, 6 and 8 A molecule of IL consists of a cation and an anion. There are three approaches for modeling such a molecule. The first one is to neglect the ionization and consider a molecular structure. Second approach is to assume a full ionic dissociation and neglect the presence of molecular ILs. A newer approach is to account for the degree of dissociation, where the system consists of molecular IL, cations and anions. The latter approach is based on experimental investigations available in literature The basis of statistical thermodynamics in the PC-SAFT equation of state has led the model to give reasonable results in this study. It is shown that accounting for the degree of ionic dissociation improves the performance of model over the case which assumes fully dissociation of IL molecules. Also, accounting for association interactions leads to significant improvement in accuracy of results