Effect of water addition on extraction ability of eutectic solvent choline chloride+1,2-propanediol for separation of hexane/heptane plus ethanol systems

Abstract

The ability of binary deep eutectic solvent choline chloride+1,2-propanediol (DES1; 1 : 3 mole ratio) and ternary deep eutectic solvent choline chloride+1,2-propanediol+water (DES2; 1 : 3 : 3 mole ratio) for breaking the azeotropes hexane/heptane+ethanol by means of liquid-liquid extraction was evaluated. Liquid-liquid equilibrium experiments were performed at 298.15 K, at atmospheric pressure, and data were correlated by NRTL and UNIQUAC models. Thermodynamic properties (density, viscosity, refractive index and speed of sound) of DES1 and DES2 were determined in temperature range from 288.15 K to 333.15 K and at atmospheric pressure. Extraction ability of the investigated eutectics yielded promising results in comparison with conventional solvents. Besides a high selectivity towards ethanol, an advantage of DES2 is its lower viscosity and higher distribution ratio values, which is an important aspect for a potential industrial application. Another advantage of both investigated eutectics is their easy and high recoverability from the extract layer based on their negligible vapor pressure.