Thermodynamics and activity coefficients at infinite dilution for organic compounds and water in the ionic liquid 1-butyl-3-methylimidazolium perchlorate

Abstract

Activity coefficients at infinite dilution (γi∞) and (gas–liquid) partition coefficients (KL) for organic compounds (alkanes, alkenes, alkyl benzenes, acetonitrile, acetone, tetrahydrofuran, ethyl acetate, 1,4-dioxane, chloromethanes, and alcohols) and water in the ionic liquid (IL) 1-butyl-3-methylimidazolium perchlorate ([BMIM][ClO4]) have been measured by the (gas-liquid) chromatographic method in the temperature range of (303.15–353.15)K. Density, ρ as a function of temperature for [BMIM][ClO4] at pressure p=101.3kPa were measured. The values of the partial molar excess enthalpies at infinite dilution (H¯iE,∞) were derived from the temperature dependence of the γi∞ values. The entropies (TrefS¯iE,∞) and Gibbs free energies (G¯iE,∞) of organic solutes in [BMIM][ClO4] at a reference temperature Tref=298.15K were also calculated from the γi∞ values. The Hildebrand’s solubility parameters of the IL [BMIM][ClO4] were also determined by the regular solution theory (RST) combined with Flory ‘‘combinatorial’’ equation. Selectivity (Sij∞) and capacity (kj∞) at infinite dilution at 323.15K have been determined for n-hexane (i)/benzene (j), cyclohexane (i)/benzene (j)). The results were analyzed in comparison to literature values for 1-buthyl-3-methylimidazolium-based ionic liquids (ILs) for the same separation problems. For three isomeric xylenes separation problems, selectivity at 323.15K were also obtained from the γi∞ values.