Design optimization of deep eutectic solvent composition and separation performance of cyclohexane and benzene mixtures with extractive distillation

Abstract

Deep eutectic solvents (DESs) have properties that make them suitable candidates to be used as entrainers for extractive distillation. In the previous work, it was proven that DES(1:2) (tet-rabutylammonium bromide: levulinic acid, 1:2, molar ratio) can break the cyclohexane-benzene aze-otrope. In the present work, the HBA and HBD ratio and molar concentration of DES were optimized to obtain a better constitute and condition of DES to be utilized in cyclohexane and benzene extractive distillation. The physical properties and structure of the prepared DESs were character-ized. Vapor–liquid equilibrium data of the ternary system (benzene + cyclohexane + DESs) were also measured at atmospheric pressure. All experimental equilibrium data were correlated with Wilson, nonrandom two-liquid (NRTL), and universal quasichemical (UNIQUAC) activity coefficient models, from which the coefficient of determination (R2) of the three pseudo-ternary systems fitting was calculated. From the obtained results, the best HBA and HBD ratio in the DESs is eluci-dated as 1:2, the best molar concentration of DES is 0.1, and the NRTL model predicts the experimental data more accurately than the Wilson and UNIQUAC models. From the derived mechanism, the formation of stronger hydrogen bond and π–π bond interactions between DES and benzene is obtained when HBA and HBD ratio in DES is 1:2. In other conditions, the azeotrope cannot be bro-ken, or the efficiency is low. The present work provides an environmentally friendly method to separate aromatic/aliphatic mixtures and act as a guide for further study of DESs in extractive dis-tillation.