Activity coefficients at infinite dilution measurements for organic solutes in the ionic liquid trihexyltetradecylphosphonium-bis-(2,4,4-trimethylpentyl)-phosphinate using g.l.c. at T = (303.15, 308.15, 313.15, and 318.15) K

Abstract

A new phosphonium ionic liquid was investigated as a possible solvent for use in the separation of aromatic hydrocarbons from aliphatic hydrocarbons. The activity coefficients at infinite dilution, γ 13 ∞ , for 14 solutes: n-alkanes, alk-1-enes, alk-1-ynes, cycloalkanes, and aromatic hydrocarbons in the ionic liquid trihexyltetradecylphosphonium-bis-(2,4,4-trimethylpentyl)-phosphinate [3C 6C 14P][(C 8H 17) 2PO 2] were consequently determined by gas–liquid chromatography at four temperatures T = (303.15, 308.15, 313.15, and 318.18) K. The partial molar excess enthalpies at infinite dilution values, Δ H 1 E, ∞ , were calculated from experimental γ 13 ∞ values obtained over the temperature range studied. The selectivities for the n-hexane/benzene, hex-1-yne/benzene, and cyclohexane/benzene separations scenarios were calculated from the γ 13 ∞ and were compared to studies from the recent literature for results of other ionic liquids, as well as NMP and sulfolane, taken from the recent literature. The results indicate that [3C 6C 14P][(C 8H 17) 2PO 2] would make a poor solvent for the separation of an alkane or alk-1-ene or cycloalkene from benzene. The results do, however, expand our knowledge and point to some interesting facets of (solute + ionic liquid) interactions.