Separation of fuel additives based on mechanism analysis and thermodynamic phase behavior

Abstract

tert-butanol and ethyl acetate, as fuel additives and oxygenated fuels, can improve fuels quality and reduce exhaust emissions. Therefore, the recovery of these compounds from azeotropic systems is of great significance. Ionic liquids (ILs) are promising green solvents for separating azeotropic systems. In this study, an efficient extraction strategy based on 1-butyl-3-methylimidazolium acetate ([Bmim][AC]) is proposed. The mechanism by which ILs enable the separation of binary alcohol-ester azeotropes was revealed by evaluating the lowest conformational energy through combining an independent gradient model based on the Hirshfeld partition (IGMH) and frontier molecular orbitals, to preliminarily screen the extractants. The range of extractants was further reduced by a vapor–liquid phase equilibrium (VLE) experiment, and a modeling method for separating the alcohol–ester system and recovering the solvent using [Bmim][AC] and 1-ethyl-3-methyl-3-imidazolium acetate ([Emim][AC]) is established. Under the optimal operating conditions, the use of [Bmim][AC] can reduce the total annual cost (TAC) per year by 17.78%, and the emissions of CO2, SO2, and NO can be reduced by 10.86%. In this study, a comprehensive method for screening extractants is proposed, and the simulation process is optimized in combination with the economic and environmental impact. The results have important guiding significance for realizing efficient, energy-saving, and green azeotropic separation systems in industry.