Activity coefficients at infinite dilution of organic solutes in the ionic liquid trihexyl(tetradecyl)phosphonium tetrafluoroborate using gas–liquid chromatography at T = (313.15, 333.15, 353.15, and 373.15) K

Activity coefficients at infinite dilution have been measured by gas–liquid chromatography for 27 organic solutes (n-alkanes, 1-alkenes, 1-alkynes, cycloalkanes, aromatics, alcohols, and ketones) in the ionic liquid trihexyl(tetradecyl)phosphonium tetrafluoroborate [3C6C14P][BF4]. The measurements were carried out at four different temperatures viz.T = (313.15, 333.15, 353.15, and 373.15) K. From the experimental data, partial molar excess enthalpy values at infinite dilution were calculated for the experimental temperature range. The selectivity values for the separation of n-hexane/benzene, cyclohexane/benzene, and methanol/benzene mixtures were determined from the experimental infinite dilution activity coefficient values. These values were compared to those available in the literature for other ionic liquids and commercial solvents, so as to assess the feasibility of employing [3C6C14P][BF4] in solvent-enhanced industrial separations.

Research highlights
► Activity coefficients at infinite dilution in the ionic liquid [3C6C14P][BF4].
► Twenty-seven solutes investigated at T = (313.15, 333.15, 353.15, and 373.15) K.
► [3C6C14P][BF4] shows promise for the separation of aromatic and alcohol mixtures.