Thermodynamics and activity coefficients at infinite dilution for organic solutes in the ionic liquid 1-butyl-1-methylpyrrolidinium dicyanamide

Abstract

The activity coefficients at infinite dilution, γ13∞, for 46 solutes, including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, thiophene, ethers, ketones, esters, aldehyde, acetonitrile, pyridine and 1-nitropropane in the ionic liquid (IL) 1-butyl-1-methylpyrrolidynium dicyanamide, [BMPYR][DCA] were determined by gas-liquid chromatography at five temperatures in range of (313.15–373.15) K at pressure, p = 101 kPa. The thermodynamic functions at infinite dilution as partial molar excess Gibbs free energy, ΔG1E,∞, enthalpy ΔH1E,∞, and entropy term TrefΔS1E,∞ and the gas-liquid partition coefficients, KL at infinite dilution were calculated from the experimental γ13∞ values obtained over the temperature range. The values of selectivity and capacity for few separation problems as n-heptane/benzene, n-heptane/thiophene, n-heptane/1-heptyne, and ethylbenzene/styrene at T = 323.15 K were calculated from γ13∞ and compared to literature values for [DCA]-based ionic liquids and [BMPYR]-based ILs. In comparison with the former measured [BMPYR][TCM], or [BMPYR][SCN] ILs, the [DCA]-based IL presents high selectivities for the separation of aromatic hydrocarbons from aliphatic hydrocarbons, and especially for the extraction of thiophene, or pyridine from n-heptane with slightly lower capacity than those for [BMPYR][TCM], or [BMPYR][SCN]. New data shows that [BMPYR][DCA] IL may be proposed as an alternative solvent for the separation of aliphatic from aromatic hydrocarbons.