Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

The distillation of azeotropic mixtures is widely performed in the fields of pharmaceuticals, petroleum, and chemical industries. Deep eutectic solvents (DESs) are environmentally-friendly entrainers that have many properties similar to ionic liquids (ILs), but are also simple in preparation and cheap in price. The ethanol + water system is a typical azeotropic mixture. In this work, the relative volatility of ethanol and water at the azeotropic point was increased from 1.00 (0 mass % choline chloride (ChCl)/urea (1:2 mol/mol)) to 4.70 (51.0 mass % ChCl/urea (1:2)). ChCl/urea (1:2) showed a remarkable entrainer performance for this separation. Isobaric vapor liquid equilibrium (VLE) data of four systems, water + ethanol, water + ChCl/urea (1:2), ethanol + ChCl/urea, and water + ethanol + ChCl/urea (at 10, 20, and 30 mass %), were determined by a modified Othmer equilibrium still at 101.32 kPa. After addition of ChCl/urea (1:2), the azeotropic point of the ethanol + water mixture was eliminated. The parameters of the nonrandom two-liquid (NRTL) model for these systems were obtained and the predicted values of these systems were found to fit the experimental VLE data quite well.