Glycerol-Based Deep Eutectic Solvents as Extractants for the Separation of MEK and Ethanol via Liquid–Liquid Extraction

Four different glycerol-based deep eutectic solvents (DESs) were tested as extracting agents for the separation of the azeotropic mixture {methyl ethyl ketone + ethanol} via liquid–liquid extraction. The selected DESs for this work were: glycerol/choline chloride with molar ratios (4:1) and (2:1), and glycerol/tetramethylammonium chloride with molar ratios (4:1) and (2:1). The selected DESs have been characterized by measuring the density and the viscosity at different temperatures. The liquid–liquid equilibria data of the ternary systems {methyl ethyl ketone + ethanol + DES} were experimentally determined at T/K = 298.15 and atmospheric pressure. The extraction efficiencies of the selected DESs were analyzed by determining the solute distribution coefficients and the selectivity values, which were calculated from the experimental results. The extraction performance of the DESs was compared to the extraction data of pure glycerol. The integrity of the DESs after recovery was also studied. Finally, the experimental LLE data were regressed using the nonrandom two liquid (NRTL) model. It was found that the addition of a hydrogen bond acceptor to glycerol, and therefore, the formation of a deep eutectic solvent, improves the extraction efficiency of this mixture via liquid–liquid extraction.