Structure-activity relationship and experimental study of organic solvents and deep eutectic solvents in separation of cyclohexane-ethyl acetate

Selecting the appropriate extractant is of great significance for solving the problems of high energy consumption and difficult separation in the extractive distillation process. In this study, four deep eutectic solvents (DESs) were designed by combining menthol hydrogen bond acceptors with lauric acid and capric acid hydrogen bond donors and tetrabutylammonium bromide hydrogen bond acceptors with levulinic acid and ethylene glycol hydrogen bond donors. The interaction mechanism and structure–activity relationship between azeotropic system, hydrogen bond donor, hydrogen bond acceptor and deep eutectic solvent were studied. σ-profile, interaction energy, reduced density gradient, electrostatic potential, and natural bond orbital were used to study the microscopic mechanism and structure–activity relationship of azeotropes separated by DESs. On this basis, the vapor–liquid equilibrium experiments of separating ethyl acetate-cyclohexane azeotrope by DESs were carried out. The results showed that separating ethyl acetate-cyclohexane by using DESs is feasible and that the DES synthesized by using levulinic acid and tetrabutylammonium bromide is preferable for separation. Studying the relationship between DES structures and the azeotrope provides a theoretical basis for the screening and design of DES extractants for the separation of alkane-ester azeotropes using extractive distillation.