Screening of Ionic Liquids for the Separation of Aromatics via Activity Coefficients at Infinite Dilution Measurements and COSMO-RS Modeling

This manuscript focuses on the application of imidazolium-based ionic liquids (ILs) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]+[PF6]−) and 1-butyl-3-methylimidazolium bis(trifluoromethane)sulfonimide ([BMIM]+[TFSI]−) as potential entrainers for the separation of cyclohexane/benzene and heptane/toluene utilizing gas liquid chromatography (GLC) technique. The activity coefficients at infinite dilution γ13∞ were obtained for 20 solutes including both polar and nonpolar in each IL at different temperatures ranging from 323.15 to 363.15 K and at pressure 101.3 kPa. The COSMO-RS model was applied to predict experimental data and to assess the solvent–solute interactions. The results indicate that the COSMO-RS model is an effective screening tool, offering a cost-effective and time-saving alternative to extensive experimental procedures. Partial molar excess enthalpies at infinite dilution, ΔH1E,∞, selectivities, Sij∞, and capacities, kj∞, were also determined for each of the separations studied. The extraction efficiency of the evaluated ILs was also compared with previously studied ILs and conventional solvents such as NMP and sulfolane which are available in the literature. Based on the findings, the activity coefficients and intermolecular interactions of different solutes in ILs are highly dependent on the chemical structure of the IL. Moreover, it also determines the enthalpy behavior of the binary mixture.