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Ionic liquids (ILs) as separating agents have been extensively studied in chemical separation processes. For IL-containing systems, the UNIFAC model for ILs (i.e., UNIFAC-Lei model) has become a po...

A united chemical thermodynamic model, that is, the COSMO-UNIFAC model, was first proposed to predict the phase equilibrium of multicomponent systems in which the UNIFAC model parameters are missing. This model combines the advantages of the UNIFAC model (accurate prediction) and the COSMO-based models (a priori prediction). The predicted vapor–liquid equilibrium results by the COSMO-UNIFAC model were compared with experimental data from the literature and this work, confirming that it can provide a moderate quantitative prediction even if the UNIFAC model parameters are missing.

Vapor pressure data for the binary systems (water/methanol/ethanol + 1-ethyl-3-methylimidazolium acetate ([EMIM]+[Ac]−)) and the ternary systems (methanol + water + [EMIM]+[Ac]−, ethanol + water + [EMIM]+[Ac]−, and methanol + ethanol + [EMIM]+[Ac]−) were measured by a modified equilibrium still. For the above systems, the maximum average relative deviation between experimental data and the UNIFAC-Lei model predicted values was 7%, confirming the prediction accuracy of the UNIFAC-Lei model. Thus, this model was further used to predict the isobaric vapor–liquid equilibrium (VLE) data at 101.3 kPa for the methanol + water + [EMIM]+[Ac]−, ethanol + water + [EMIM]+[Ac]−, and methanol + ethanol + [EMIM]+[Ac]− systems at a fixed mole fraction of ionic liquid (IL) (xIL = 0.2). It was demonstrated that the ionic liquid [EMIM]+[Ac]− was an appropriate entrainer to separate the methanol–ethanol–water mixture. On this basis, the extractive distillation process was simulated using the rigorous equilibrium (EQ) stage m...