Separation of the ethanol/water azeotropic mixture using ionic liquids and deep eutectic solvents

Abstract

Two ethanolamine-based ionic liquids (ILs) and two choline chloride-based deep eutectic solvents (DESs) were synthesized and evaluated as entrainers for the separation of the ethanol/water azeotropic mixture. Isobaric vapor-liquid equilibrium data of the ternary system ethanol/water/IL or DES were measured using an ebulliometer at 101.3kPa. The ILs examined were 2-hydroxy ethylammonium acetate and 2-hydroxy ethylammonium hexanoate, while the DESs were choline chloride:urea (1:2) and choline chloride:triethylene glycol (1:3). In all cases, an increase of the relative volatility and, consequently, a displacement of the azeotropic point was observed. Depending on the entrainer, concentrations of about 5.5–9% (w/w) were adequate for the complete elimination of the azeotrope. Recoverability and biodegradation tests were carried out for all ILs and DESs. DESs were found to be biodegradable, while ILs exhibited lower biodegradation capacity than DESs. Furthermore, analysis with 1H NMR proved that all entrainers can be recycled and reused. Finally, thermodynamic modeling of the ethanol/water/IL or DES mixtures was performed with the UNIQUAC and NRTL models. The results for both models were found to be in good agreement with the experimental data.