Vapour-liquid equilibria of systems containing deep eutectic solvent based on choline chloride and glycerol

Abstract

Deep eutectic solvents (DES) have been recently proposed as potential entrainers for extractive distillation to obtain anhydrous ethanol. However, the lack of thermodynamic data of mixtures containing DESs still hampers studies of their application in separation processes. In this work, the DES based on choline chloride and glycerol (ChCl:G) at the molar ratio of 1:2 was proposed as extracting solvent for ethanol dehydration. Therefore, the vapour-liquid equilibrium (VLE) of the pseudo-binary systems {water - ChCl:G(1:2.000) & ethanol - ChCl:G(1:2.000)} were measured at 11.3 kPa. The pseudo-ternary VLE data of {ethanol–water-ChCl:G(1:2.000)} were also obtained, keeping the concentration of ChCl:G(1:2.000) nearly constant (x3 = 0.50). The experimental VLE data were correlated to non-random two-liquid (NRTL) and universal quasichemical (UNIQUAC) models aiming to calculate the interaction binary parameters. Through the overall average errors, it was concluded that the UNIQUAC model describes better the binary systems {ethanol - ChCl:G(1:2.000)} (0.465%) while NRTL is more suitable to describe the system {water - ChCl:G(1:2.000)} (0.113%). However, the pseudo-ternary system {ethanol – water – ChCl:G (1:2.000)} could not be successfully represented by the coefficients obtained from the binary data. In addition, the VLE results of the pseudo-ternary system demonstrated that ChCl:G(1:2.000) increased the relative volatility of ethanol–water, indicating the potential use of ChCl:G(1:2.000) in the production of anhydrous ethanol through extractive distillation.