Thermodynamics and activity coefficients at infinite dilution for organic solutes, water and diols in the ionic liquid choline bis(trifluoromethylsulfonyl)imide

Abstract

The activity coefficients at infinite dilution, γ13∞, for 63 solutes, including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, thiophene, ethers, ketones, esters, aldehyde, acetonitrile, pyridine and 1-nitropropane and 6 diols in the ionic liquid (IL) choline bis(trifluoromethylsulfonyl)imide, [N1112OH][NTf2] were determined by (gas+liquid) chromatography at six temperatures in range of (318.15 to 368.15)K and at three temperatures for diols in the range of (388.15 to 418.15)K. The thermodynamic functions at infinite dilution as partial molar excess Gibbs free energy, ΔG1E,∞, enthalpy ΔH1E,∞, and entropy term TrefΔS1E,∞ were calculated from the experimental γ13∞ values obtained over the temperature range. The density of [N1112OH][NTf2] was measured within temperature range (313.15 to 353.15)K. The (gas+liquid) partition coefficient KL was calculated for all solutes. The values of selectivity and capacity for a few separation problems as hexane/benzene, cyclohexane/benzene, heptane/thiophene at T=328.15K were calculated from γ13∞ and compared to literature values for similar ionic liquids, N-methyl-2-pyrrolidinone (NMP), and sulfolane. In comparison with the former measured ammonium-based ILs and the morpholinium-based ILs, the [N1112OH][NTf2] shows average selectivity for the separation of aromatic hydrocarbons, or sulfur compound from aliphatic hydrocarbons, and very high selectivity for pyridine/heptane separation. New data show that [N1112OH][NTf2] IL may be proposed as an alternative solvent for the separation of sulfur or nitrogen compounds from alkanes.