Toward a Sustainable Azeotrope Separation of Acetonitrile/Water by the Synergy of Ionic Liquid-Based Extractive Distillation, Heat Integration, and Multiobjective Optimization

The sustainable separation process for the recovery of acetonitrile from wastewater is essential to achieve the circular economy and environmental protection. In this work, we demonstrate systematically a methodology to develop an energy-efficient extractive distillation process for separating the acetonitrile and water azeotrope. First, the separation performances of candidate entrainers, i.e., ionic liquids (ILs) and ethylene glycol (EG), were determined using the residue curve maps. Second, the boundaries of decision variables for optimization procedures were obtained via the sensitivity analysis, and the nonsorting genetic algorithm (NSGA-II) was applied to get the optimal operating parameters of conventional and heat-integrated schemes using EG and three ILs. Third, three indicators including the total annual cost, gas emissions, and thermodynamic efficiency were used to evaluate the economic, environmental, and energy efficiency performances of conventional and intensified schemes. Using the conventional EG process as a basis, the heat-integrated scheme using [EMIM][OAC] shows the best performance as it gives the reductions of 26.3% and 22.1% in the total annual cost and gas emissions, respectively, and an absolute increase of 0.44 in the second-law efficiency.