Design and optimization of extractive distillation of benzene–n‐propanol with ionic liquid as entrainer

Abstract BACKGROUND The binary benzene– n ‐propanol azeotrope can be formed in chemical production. Extractive distillation is an important azeotrope separation technology and an ionic liquid is a type of excellent entrainer. Aspen Plus software was used to simulate the extractive distillation process. The separation performance of ionic liquids was evaluated in terms of total annual cost of the extractive distillation process. The separation mechanism of the azeotrope was quantitatively explained using intermolecular interaction energy. RESULTS The thermodynamic properties databases of 1‐octyl‐3‐methylimidazolium acetate, trioctylmethylammonium acetate and 1‐decyl‐3‐methylimidazolium acetate were established in Aspen Plus software. The extractive distillation process was established through combining the thermodynamic properties of the three ionic liquids and the vapor–liquid equilibrium data of benzene– n ‐propanol–ionic liquid. The optimal operating conditions were obtained by minimizing the total annual cost of the separation process through a sequential iterative method. The interaction energy was calculated using density functional theory through Gaussian 09 software and used to explain the principle of the benzene– n ‐propanol azeotropic system separation. CONCLUSIONS 1‐Octyl‐3‐methylimidazolium acetate has the best separation performance among the three ionic liquids. The interaction energy can be used to screen and design ionic liquids in the process of benzene– n ‐propanol extractive distillation separation. © 2021 Society of Chemical Industry (SCI).