Process design and multi-objective optimization for separation of isopropyl acetate/isopropanol/water by extractive distillation using ionic liquid mixed solvents

Efficient recovery of isopropyl acetate and isopropanol from wastewater during esterification is important. An efficient separation process using ionic liquid mixed solvent extractive distillation (MSED) to separate azeotropic mixtures was proposed. The selectivity of 169 ionic liquids was calculated based on the COSMO–segment activity coefficient model for prescreening ionic liquids. The influence of the structure of the ionic liquids on the separation performance was further explored through molecular dynamics to determine 1-ethyl-3-methylimidazole acetate ([EMIM][AC]) as the best solvent. The vapor–liquid equilibrium of the system under the influence of [EMIM][AC] was measured to verify the model used for the calculation. A multi-objective genetic algorithm was used for optimizing the process parameters with the total annual cost (TAC) and gas emission as objective functions. An energy-saving heat-pump-assisted heat-integrated extractive distillation (HPHIED) process was proposed to realize heat recovery in MSED. The results showed that the TAC and gas emissions of MSED were 26.83% and 25.32%, respectively, lower than those of the single-organic solvent extractive distillation process. The TAC and gas emissions of HPHIED process were 11.02% and 35.83%, respectively, lower than those of MSED.