Activity coefficients at infinite dilution measurements for organic solutes in the ionic liquid 1-butyl-3-methyl-imidazolium 2-(2-methoxyethoxy) ethyl sulfate using g.l.c. at T = (298.15, 303.15, and 308.15) K

Abstract

The activity coefficients at infinite dilution, γ 13 ∞ (where 1 refers to the solute and 3 to the solvent), for both polar and non-polar solutes in the ionic liquid 1-butyl-3-methyl-imidazolium 2-(2-methoxyethoxy) ethyl sulfate have been determined by gas-liquid chromatography. The interaction at the gas-liquid interface between the solutes and the solvent was examined by varying solvent liquid loading on the column. Corrected retention values, taking carrier gas and solute imperfections into account, were determined and used to calculate the activity coefficients at infinite dilution. In this work the activity coefficients at infinite dilution for various solutes (alkanes, alk-1-enes, alk-1-ynes, cycloalkanes, aromatic hydrocarbons, carbon tetrachloride and methanol) in the ionic liquid were measured at three temperatures T = (298.15, 303.15, and 308.15) K. This investigation is related to our previous work on the measurement of γ 13 ∞ in the ionic liquid solvents: 1-methyl-3-octyl-imidazolium chloride or 1-hexyl-3-methyl-imidazolium tetrafluoroborate or 1-hexyl-3-methyl-imidazolium hexafluorophosphate or 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl) imide.The results have again been used to predict the solvent potential for the hexane/benzene separation from calculated selectivity values. The results are compared to γ 13 ∞ for similar systems found in the literature in an attempt to understand the effect the nature of the cation and anion has, on solute–solvent interactions. The partial molar excess enthalpies at infinite dilution values, Δ H 1 E ∞ , were calculated from the experimental γ 13 ∞ values obtained over the temperature range.