The mechanism explosion of separating binary azeotropic system with intermediate-boiling-point solvent based on vapor–liquid equilibrium experiment, quantum chemical calculation and molecular dynamics simulation

Abstract

For the extraction distillation process, the choice of entrainer is very important. Usually, the boiling point of the entrainer is higher than that of any of the components to be separated, while the mechanism of separation of azeotropic system with intermediate-boiling-point solvent as entrainer is not common. Taking the azeotrope of n-heptane and isopentyl alcohol as an example, the intermediate-boiling-point solvent of butyl acetate was determined as the entrainer. The experimental data of vapor–liquid equilibrium for the two systems of n-heptane isoamyl alcohol and n-heptane butyl acetate were analyzed. After the thermodynamic consistency test, the binary interaction parameters of three models were obtained by correlating and regressing the experimental data. The possibility and mechanism of the extraction of azeotropic system by the intermediate-boiling-point solvent were analyzed from the aspects of σ-profile, interaction energy and charge density by the principle of quantum chemistry and molecular dynamics. The results showed that the tendency of hydrogen bond between the intermediate-boiling-point solvent and the azeotropic system was different: one component interacted with each other in the form of hydrogen bond, and the other had no hydrogen bond. The mechanism of the intermediate-boiling-point solvent as the entrainer to separate azeotropic system was verified in the extractive distillation process.