Pre-screening of an eco-friendly solvent for separating industrial mixtures: A useful tool for solvent selection

Abstract

In this work, gas liquid chromatography was used to obtain the retention data of volatile organic solvents (here referred as solutes) at different temperatures, T = (313.15 - 353.15) K and at atmospheric pressure. The retention data obtained was used to compute the activity coefficients at infinite dilution. The solvent was prepared by the combination of 1‑butyl‑2,3-dimethylimidazolium chloride and diethylene glycol at 1:2 molar ratio and was used as a stationary phase to evaluate intermolecular interactions of various volatile organic solvents, including (aromatic hydrocarbons, ketones, alkanes, alkenes, alkynes, alcohols, thiophene, acetonitrile and tetrahydrofuran). Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectroscopy were utilized to determine any possible shifts when the two compounds were assorted. TGA/DSC 1 was also utilized to determine the thermal stability of the investigated solvent and to confirm that there will be no bleeding on the column loading when operated at T = (313.15 - 353.15) K. The excess thermodynamic properties at infinite dilution including enthalpies, Gibbs free energies and entropy term were computed to further explain the types of interactions occurring between the systems. The activity coefficients at infinite dilution data were used to calculate the separation parameters (selectivity and capacity) to evaluate the feasibility of the solvent in separating the industrial mixtures. Values pertaining to selectiveness and capacity were evaluated and compared to other extracting solvents found in literature for the separation of azeotropic mixtures. The attained activity coefficients at infinite dilution data reveals that the investigated solvent better separate solutes at low temperatures and this is an added advantage when using 1‑butyl‑2,3-dimethylimidazolium chloride to diethylene glycol. In addition, the investigated solvent was found suitable for the extraction of azeotropic mixtures comprising alkanes and alcohols.