Energy-Saving Processes Design and Multi-Objective Optimization for Ethyl Acetate and N-Heptane Separation by Extractive Distillation

Ethyl acetate and n-heptane are important chemical products with excellent chemical properties, which are often used as mixed solutions. However, the mixed solutions of ethyl acetate and n-heptane are difficult to recover because the lowest azeotrope will be formed. Herein, an extractive distillation separation process was proposed to realize the separation of ethyl acetate and n-heptane. p-Xylene and N-methylpyrrolidone were selected as extractants. Then the COSMO-SAC model was established based on Aspen Plus database, and the process was optimized by Aspen Plus. The processes were evaluated by the total annual cost, energy consumption and CO2 emission. Compared with the extractive distillation process with N-methylpyrrolidone as extractant, total annual cost, energy consumption and CO2 emission of the process with p-xylene as extractant were reduced by about 16.50 %, 16.78 % and 25.24 %, respectively. On this basis, the heat pump assisted distillation processes were further developed. The heat pump distillation process with an overhead steam preheater once again realized the reduction of all evaluation parameters, and the total annual cost, energy consumption and CO2 emission were reduced by about 16.78 %, 28.12 % and 41.83 %, respectively. It provided guidance for the separation of ethyl acetate and n-heptane.