Sustainable Process Design and Multiobjective Optimization for Separation of n-Heptane/tert-Butyl Acetate by Extractive Distillation: from Separation Mechanism to Experimental

Since tert-butyl acetate and n-heptane can form binary azeotropes, in this study, two special distillation methods of extractive distillation (ED) and improved side-stream extractive distillation were used to separate tert-butyl acetate and n-heptane. First, considering the properties of molecular bond energy, relative volatility, and azeotrope formation, n-methylpyrrolidone (NMP) was selected as the most suitable solvent. Subsequently, the missing binary interaction parameters for N-HEP-01/T-BUT-TE and NMP/T-BUT-TE were obtained by a vapor–liquid equilibrium experiment. Furthermore, multiobjective optimization was performed to minimize the total annual cost (TAC), entropy generation, and CO₂ emissions. The results indicate that energy consumption of the side-stream extractive distillation process was reduced by 1.3% compared with the ED process, but TAC increased by 8.53%. To further enhance energy savings, heat integration technology was introduced to save more energy. Compared to conventional ED, the heat integration-assisted extractive distillation (EDH2) process reduces TAC by 28.84%, entropy generation by 33.17%, and CO₂ emissions by 42.28%.