Activity coefficients at infinite dilution of alkanes, alkenes, alkyl benzenes in dimethylphosphate based ionic liquids using gas–liquid chromatography

Abstract

Activity coefficients at infinite dilution (γi∞) for organic solutes: alkanes, alkenes, and alkyl benzenes in two ionic liquids (ILs) 1,3-dimethylimidazolium dimethylphosphate ([MMIM][DMP]) and 1-ethyl-3-methylimidazolium dimethylphosphate ([EMIM][DMP]) have been measured by the gas–liquid chromatographic method (GLC). The measurements were carried out in the temperature range of (313.15 to 363.15)K. 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 energies (G‾iE,∞) of organic solutes at a reference temperature Tref=298.15K were also calculated from the γi∞ values. Selectivity (Sij∞) and capacity (kj∞) at infinite dilution at T=323.15K have been determined for hexane (i)/benzene (j), cyclohexane (i)/benzene (j). The results were analyzed in comparison to literature data for other ILs with the [MMIM] and [EMIM] cations. For three isomeric xylenes separation problems, selectivity at T=323.15K were also obtained from the γi∞ values.