Measurement of Vapor–Liquid Equilibrium for Dichloromethane + Alkyl Sulfate-Based Ionic Liquid Systems

Ionic liquids (ILs) show great potential for the treatment of dichloromethane (DCM)-containing waste gases, but currently there are limited data on the vapor–liquid equilibrium (VLE) of DCM + IL systems. This work uses headspace gas chromatography (HS-GC) to determine the isothermal VLE data of the DCM + [Epy][EtSO4] and DCM + [Emim][EtSO4] systems at 308.15 K, 313.15 K, 318.15 K, 323.15 K, and 328.15 K. The nonrandom two-liquid (NRTL) and universal quasi-chemical correlation activity coefficient (UNIQUAC) models are used to regress the VLE data. The results show that the fitting average relative deviations (ARDs) of the DCM + [Epy][EtSO4] and DCM + [Emim][EtSO4] systems to the NRTL model were 6.97% and 7.95% and the fitting ARDs to the UNIQUAC model were 6.10% and 6.28%, respectively. The fitting effects of the UNIQUAC models for both systems were better than those of the NRTL model. With the models, the calculated activity coefficients of DCM were all less than 1, indicating that the solutions exhibited negative deviations from Raoult’s law, and the nonideality of the solutions increased with increasing IL concentration.