Thermodynamics and activity coefficients at infinite dilution for organic solutes in the ionic liquid 1-hexyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide

Abstract

Activity coefficients at infinite dilution (γi∞) and gas-liquid partition coefficients (KL) for organic solutes: n-alkanes, alkenes, alkyl benzenes, acetonitrile, acetone, tetrahydrofuran, ethyl acetate, and chloromethanes in the ionic liquid (IL) 1-hexyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide ([HMMIM][NTf2]) have been measured by the gas-liquid chromatographic method (GLC) in the temperature range of (313.15–353.15)K. The thermodynamic functions at infinite dilution as partial molar excess enthalpies at infinite dilution (H‾iE,∞) were derived from the temperature dependence of the γi∞ values. Gibbs energies (G‾iE,∞) and entropies (TrefS‾iE,∞) of organic solutes in [HMMIM][NTf2] at a reference temperature Tref=298.15K were also calculated from the γi∞ values. The solubility parameters of the IL [HMMIM][NTf2] were determined by two methods. 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 data for alkylimidazolium-based ILs with [NTf2]−. For three isomeric xylenes separation problems, selectivity at 323.15K were also obtained from the γi∞ values.