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

Background: 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. Methods: 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 dihydmgen 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 Dmol(3) in Materials Studio, and the interactions between molecules were explored. Significant findings: The experimental data showed that the three ILs can extract IPA from the mixture of IPAC and IPA and the IL [Bmim] [Hi(2)PO(4)] 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.

Automated summary

In this study, liquid-liquid extraction was used to separate the mixture of IPAC and IPA, with three ionic liquids demonstrated as effective extractants, particularly [Bmim] [Hi(2)PO(4)]. The experimental data was fitted using the NRTL model to optimize the separation process for industrial applications.