Activity coefficients at infinite dilution of organic solutes in the ionic liquid, methyl(trioctyl)ammonium thiosalicylate, [N1888][TS] by gas–liquid chromatography at T = (303.15, 313.15, and 323.15) K

In this work, activity coefficients at infinite dilution (γ13∞) have been obtained for 19 polar and non-polar organic solutes in the form of n-alkanes, cycloalkanes, 1-alkenes, 1-alkynes, aromatic compounds, and ketones in the ionic liquid methyl(trioctyl)ammonium thiosalicylate by gas–liquid chromatography at three different temperatures, i.e. T = (303.15, 313.15, and 323.15) K. Two columns with different phase loadings of the ionic liquid in the stationary phase (25% and 30%) were employed to obtain γ13∞ values at each temperature investigated. Partial molar excess enthalpies at infinite dilution (ΔH1E,∞) were calculated for each of the solutes from the temperature dependency of the γ13∞ values for the temperature range in this study. Selectivity values at infinite dilution (Sij∞) were computed from the γ13∞ values to screen the potential candidacy of the ionic liquid for the separation of n-hexane/benzene mixtures. The results from this study have been compared to those available for several other classes of ionic liquids and commercial solvents employed in solvent-enhanced industrial separation processes.

Research highlights
► Ammonium ionic liquid selectivity value lower than for imidazolium ionic liquid.
► Ammonium ionic liquids with smaller alkyl groups have higher selectivity values.
► For the same cation the [TS] anion has a higher selectivity than the [NTf2].