Isobaric vapor-liquid equilibrium oftert-butanol plus water plus ionic liquids at atmospheric pressure

BACKGROUND tert-Butanol (TBA) and water form an azeotrope at atmospheric pressure. Therefore, extractive distillation was adopted to separate the azeotropic mixture. As a new kind of solvent, the ionic liquids (ILs) 1,3-dimethylimidazolium dimethylphosphate ([MMIM][DMP]) and 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]) were chosen to break the azeotropic point in extractive distillation. RESULTS For the ternary mixture of TBA + water + ILs, the isobaric vapor-liquid equilibrium data at atmospheric pressure for three IL mole fractions (0.1, 0.2 and 0.3) were measured. The results indicated that the volatility of TBA relative to water became higher after [MMIM][DMP] or [EMIM][DEP] was added. The nonrandom two-liquid (NRTL) model and the COSMO-RS theory were used to predict the ternary experimental data. The predicted results from the NRTL model showed good agreement with the experimental data. The predicted results from COSMO-RS showed that the vapor-phase mole fraction basically agreed with the experimental data and the equilibrium temperatures were lower than the experimental data.sigma-Profiles,sigma-potentials and sigma-surfaces were calculated based on COSMO-RS. The results were the same as for the experiments, namely the interaction between water and ILs was stronger than other interactions; the affinity of water and [MMIM][DMP] was stronger than that of water and [EMIM][DEP]. CONCLUSIONS The separation of the binary azeotrope of TBA and water was achieved after the ILs [MMIM][DMP] or [EMIM][DEP] were added. The separation ability of [MMIM][DMP] was better than that of [EMIM][DEP]. (c) 2020 Society of Chemical Industry

Automated summary

In this study, ionic liquids were used to separate the azeotropic mixture of TBA and water. Experimental results showed that the addition of [MMIM][DMP] or [EMIM][DEP] increased the volatility of TBA relative to water. Predictions from the NRTL model and COSMO-RS theory matched well with the experimental data, indicating the effectiveness of using ILs for extractive distillation.