Thermodynamics and activity coefficients at infinite dilution measurements for organic solutes and water in the ionic liquid N-hexyl-3-methylpyridinium tosylate.

The activity coefficients at infinite dilution, γ13(∞), for 44 solutes, including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, thiophene, tetrahydrofuran, ethers, and ketones in the ionic liquid (IL) N-hexyl-3-methylpyridinium tosylate (p-toluenesulfonate), [HM3Py][TOS], were determined by gas-liquid chromatography at temperatures from 338.15 to 368.15 K. The densities of [HM3Py][TOS] as a function of temperature have been measured at temperatures higher than the melting temperature and were extrapolated to T = 298.15 K. The gas-liquid partition coefficients, K(L) were calculated for all solutes. The partial molar excess Gibbs energies ΔG1(E,∞), enthalpies ΔH1(E,∞), and entropies ΔS1(E,∞) at infinite dilution were calculated from the experimental γ13(∞) values obtained over the temperature range. The selectivities for different separation problems including n-heptane/benzene, cyclohexane/benzene, and n-heptane/thiophene were calculated from γ13(∞) and compared to literature values for tosylate-based ILs, or hexyl-substituted cations of ILs, or pyridynium-based IL, or N-methyl-2-pyrrolidinone (NMP), and sulfolane.