Separation of azeotropic mixtures (ethanol and water) enhanced by deep eutectic solvents

The distillation of azeotropic mixtures is commonly and widely performed in the pharmaceutical, 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. Also, the ethanol/water system is a typical industrial azeotropic mixture. In this work, the relative volatility of ethanol and water at the azeotropic point was increased from 1.00 to 4.70 with 0–51.0 mass % ChCl/urea (1:2, mol/mol), with ChCl/urea showing a remarkable entrainer performance in this separation. Isobaric vapor–liquid equilibrium (VLE) data of four systems, water + ethanol, water + ChCl/urea, ethanol + ChCl/urea, and water + ethanol + ChCl/urea (at 10, 20, and 30 mass%), were determined using a modified Othmer equilibrium still at 101.32 kPa. After addition of ChCl/urea, the ethanol + water mixture's azeotropic point was eliminated. The parameters of the nonrandom two-liquid (NRTL) model for these systems were calculated and the predicted values for these systems were found to fit the experimental VLE data quite well.