Prediction of thermodynamic properties of pure ionic liquids through extended SAFT-BACK equation of state

An analytic version of statistical associating fluid theory (SAFT), namely extended SAFT-BACK equation of state has been developed to predict the pressure–volume–temperature (pVT) and second-order thermodynamic properties of pure alkyl-imidazolium ionic liquids (ILs) with [PF6]− and [BF4]− anions. The new molecular parameters are obtained by fitting to reliable density data of pure ILs with a fitting error of 0.12% on average. The ionic liquids composed of chain-like dipolar non-spherical ion-pairs and the extended SAFT-BACK model are found to be able to correctly describe the speed of sound and isothermal compressibility as well as pVT properties of ionic liquids studied in this work.