Thermodynamics and activity coefficients at infinite dilution for organic compounds in the ionic liquid 1-hexyl-3-methylimidazolium chloride

Abstract

The activity coefficients at infinite dilution,γi∞, for 33 solutes, including alkanes, cycloalkanes, alkenes, aromatic hydrocarbons, acetonitrile, acetone, tetrahydrofuran, ethyl acetate, 1,4-dioxane, chloromethanes, alcohols in the ionic liquid 1-hexyl-3-methylimidazolium chloride, [HMIM][Cl], were determined by gas–liquid chromatography at temperatures range of (313.15–363.15) K. The gas-liquid partition coefficients,KLwere calculated for all solutes. The densities of [HMIM][Cl] were measured at the temperature range from 313.15 K to 363.15 K. The values of the partial molar excess enthalpies at infinite dilution H-iE,∞ were derived fromthe temperature dependence of the γi∞values. The entropies TrefS-iE,∞ and Gibbs energies G-iE,∞ of organic solutes in [HMIM][Cl] at a reference temperatureTref = 298.15 K were also calculated from the γi∞ values. The Hildebrand’s solubility parameters of the IL [HMIM][Cl] were also determined by the regular solution theory (RST) combined with Flory ‘‘combinatorial’’ equation. The values of selectivity and capacity for n-hexane (i)/benzene (j), cyclohexane (i)/benzene (j) were calculated from γi∞ and compared to literature values for [HMIM]-based or [Cl]-based ILs for the same separation problems.