Separation of the Dimethyl Carbonate + Ethanol Mixture Using Imidazolium-Based Ionic Liquids as Entrainers

The mixture of dimethyl carbonate (DMC) and ethanol is a common binary azeotrope system in industry that cannot be effectively separated by conventional separation methods. Two ionic liquids (ILs), namely, 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][DBP]) and 1-butyl-3-methylimidazolium acetate ([BMIM][Ac]), were tried as novel entrainers for the separation of the DMC–ethanol azeotrope. The vapor–liquid equilibrium (VLE) data of the DMC–ethanol binary system and the DMC–ethanol–ILs ternary system at atmospheric pressure were determined. The results showed that both ILs could increase the relative volatility of DMC to ethanol, thus completely breaking the azeotrope at a certain concentration, and [BMIM][Ac] had more excellent separation capacity than [BMIM][DBP]. The NRTL model and the UNIFAC-Lei model were used to correlate the experimental VLE data, and the fitting results indicated that the NRTL model was in good agreement with the experimental data.