Thermodynamic study of molecular interaction-selectivity in separation processes based on limiting activity coefficients

Abstract

Abstract The effect of interactions between organic solvents and water on the interfacial and bulk properties of N-ethyl-N-methylmorpholinium dicyanamide, [EMMor][DCA] were discussed on the base of the limiting activity coefficients γ 13 ∞ values. The experimental γ 13 ∞ values were determined by gas–liquid chromatography at temperatures from (298.15 to 368.15) K for 61 assorted solutes—among them, alkanes (linear, branched, or cyclic), alkenes, alkynes, aromatic hydrocarbons, alcohols, water, thiophene, tetrahydrofuran, 1,4-dioxane, ethers, acetone, ketones, acetonitrile, pyridine, and 1-nitropropane. The partial molar excess Gibbs free energy Δ G 1 E, ∞ , the partial molar excess enthalpy Δ H 1 E, ∞ , and entropy at reference temperature T ref Δ S 1 E, ∞ at infinite dilution were calculated from the experimental γ 13 ∞ values obtained over this temperature range. The gas–liquid partition coefficient K L was calculated for each solute and discussed in light of the Abraham solvation parameter model. The density and viscosity of the [EMMor][DCA] as a function of temperature were also measured. The selectivity and capacity for six separation problems were calculated from γ 13 ∞ and compared to literature values for selected ionic liquids. These separation problems are central to the petroleum and organic chemistry industry. The data presented here shows that [EMMor][DCA] reveals large selectivity equal 140, 273, 538, 73.1, 87.5 and 10.2 in heptane/benzene, heptane/thiophene, heptane/ethanol, hexane/ethyl acetate, ethyl-tert-butyl ether, ETBE/ethanol and THF/water separation problems at T = 328.15 K. The capacities were 0.22, 0.42, 0.83, 0.17 and 2.97 for benzene, thiophene, ethanol, ethyl acetate, and water at the same temperature.