Thermodynamics and activity coefficients at infinite dilution for organic solutes and water in the ionic liquid 1-butyl-1-methylmorpholinium tricyanomethanide

Abstract

The activity coefficients at infinite dilution, γ13∞, for 61 solutes, including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, thiophene, ethers, ketones, esters, aldehyde, acetonitrile, pyridine and 1-nitropropane in the ionic liquid (IL) 1-butyl-1-methylmorpholinium tricyanomethanide, [BMMOR][TCM] were determined by gas–liquid chromatography at six temperatures within the range of (318.15 to 368.15)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 [BMMOR][TCM] was measured over the temperature range (288.15 to 368.15)K. The gas–liquid partition coefficient KL was calculated for all solutes. The values of selectivity and capacity for a few separation problems such as hexane/benzene, cyclohexane/benzene, heptane/thiophene at T=328.15K were calculated from γ13∞ and compared to literature values for similar ionic liquids, viz. N-methyl-2-pyrrolidinone (NMP), and sulfolane. In comparison with the previously measured values for [BMPYR][TCM], the morpholinium IL presents high selectivity for the separation of aromatic hydrocarbons from aliphatic hydrocarbons, and especially thiophene, or piridine from heptane with a slightly lower capacity. New data show that [BMMOR][TCM] IL may be proposed as an alternative solvent for the separation of sulphur or nitrogen compounds from alkanes.