Screening of Imidazole Ionic Liquids for Separating the Acetone–n‑Hexane Azeotrope by COSMO-SAC Simulations and Experimental Verification

Ionic liquids have received wide attention as green recyclable extractants. In view of their broad applicability, in the current work, ionic liquids were explored for their ability to extract acetone from n-hexane. Based on the conductor-like screening model for the segment activity coefficient, the surface charge densities of 15 kinds of cations, 19 kinds of anions, acetone, and n-hexane were calculated via quantum chemistry approaches. The infinite dilution activity coefficients of the ionic liquid–acetone–n-hexane system were calculated, and the distribution coefficient and selectivity of the system were determined. The effective extractants [1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-hexyl-3-methylimidazolium bis­(trifluoromethanesulfonyl), 1-hexyl-3-methylimidazolium trifluoromethanesulfonate, and 1-hexyl-3-methylimidazolium hexafluorophosphate] were selected. The experimental data of the liquid–liquid equilibrium were correlated by the NRTL and UNIQUAC models. The regression of the experimental data gave the binary interaction parameters of the two models. In addition, a process of extracting and separating the n-hexane–acetone azeotrope system using Aspen Plus 8.4 was proposed and the parameters were analyzed. Based on the NRTL model, a continuous extraction process using ionic liquids as the extractant was simulated. Ionic liquids are a promising solvent for the extraction and separation of acetone and n-hexane.