Liquid-liquid equilibrium and insights of intermolecular interactions for separation of isopropyl acetate + isopropanol by imidazolium-based ionic liquids

During the production of isopropyl acetate (IPAC), a mixture of IPAC and isopropanol (IPA) can be produced. Because IPAC and IPA can form a minimum azeotropic mixture with the azeotropic temperature of 354.08 K, it is difficult to separate such a mixture. In this work, liquid-liquid extraction is considered to separate the mixture of IPAC and IPA. Herein, the liquid-liquid equilibrium (LLE) data was determined and correlated for the separation of IPAC and IPA. For separating IPAC and IPA by extraction, three ionic liquids (ILs) 1-ethyl-3-methyl-imidazolium hexafluorophosphate, 1‑butyl‑3-methyl-imidazolium hexafluorophosphate and 1‑butyl‑3-methyl-imidazolium dihydrogen phosphate were selected as extractants. The liquid-liquid equilibrium phase behavior of ternary mixtures (IPAC + IPA + ILs) at 298.15 K was investigated. The distribution functions of charge density and interaction energy were determined by the COSMO-SAC model and Dmol3 in Materials Studio, and the interactions between molecules were explored. The experimental data showed that the three ILs can extract IPA from the mixture of IPAC and IPA and the IL [Bmim][H2PO4] has a better extraction ability compared to the other ILs. The measured LLE data were fitted using the NRTL model and the interaction parameters were regressed, which is a favor in separating the mixture for industrial practice.