Separation of ethanol – water mixture by extractive distillation using pyridinium-based ionic liquid 1-ethyl-3-methylpyridinium ethylsulfate

Abstract

Ionic liquids (ILs) have received considerable attention for their use in chemical industry and are considered to be an alternative to conventional entrainers in extractive distillation, because of their ability to selectively separate azeotropic or close boiling mixtures. In this work, an extractive distillation process was investigated, comparing the pyridinium-based (IL) “1-ethyl-3-methylpyridinium ethylsulfate” [EMPy][ESO4] with the ethylene glycol (EG) organic solvent for the ethanol/water separation. This (IL) was proposed because of its high selectivity compared to conventional (EG). The electrolyte non-random-two-liquid (eNRTL) activity coefficient model was used to calculate the vapor-liquid equilibrium (VLE) of the ethanol-water mixture in the presence of the solvent. Indeed, the VLE behavior of ethanol-water in the presence of [EMPy][ESO4] showed that the (IL) enhances the relative volatility of ethanol and allows to eliminate the azeotrope at smaller solvent concentration, comparing to (EG). The best operating conditions of the extractive distillation process were determined for three cases of ethanol composition in feed mixture to obtain ethanol with higher purity (i.e. 99.9 mol.%). Besides, it has been found that the [EMPy][ESO4] (IL) is more efficient than EG for the separation of ethanol-water azeotropic system even at low concentrations; it is less energy consuming and more economical compared to the conventional solvent.