Extension of the F-SAC model to ionic liquids

In this work, the F-SAC model was extended to describe ionic liquids (IL). The proposed model was tested with cations of the 1-alkyl-3-methylimidazolium family (extended to 1-butyl, 1-hexyl and 1-octyl by group contribution) and six different anions. Only 25 new IL parameters were estimated based on infinite dilution activity coefficient (IDAC) data. The non-IL group parameters were retrieved from previous works, not related to IL. The obtained parameters resulted in a good agreement for 1332 IDAC points of alkanes, alkenes, cycloalkanes, cycloalkenes, aromatics, ethers, ketones, and water diluted in IL, with an absolute average deviation of 0.160 for the IDAC logarithm and R2 of 0.980. Prediction of vapor-liquid equilibria as well as liquid-liquid equilibria of binary and ternary mixtures also showed a good agreement with experimental data. Comparison with excess enthalpy data showed a good temperature dependence prediction. When compared to UNIFAC (Do), F-SAC presented similar results, but with a much smaller number of parameters needed (Unifac (Do) currently contains 163 non-zero binary parameters to describe a subset of the mixtures studied in this work).