Study Of The Ionic Liquids Effect On Liquid-liquid Behavior Of Alkane-containing Azeotropic Systems And Thermodynamic Simulation

Liquid-liquid extraction is an efficient and low-energy separation method of liquid mixtures.For the extraction and separation process of binary azeotrope formed by alkane,alcohol,ester and other substances,the key lies in the selection of extraction agent.As a"green solvent",Ionic liquid（ILs）is a highly promising extractant in liquid-liquid extraction.In this paper,the extraction and separation of n-hexane/n-heptane-alcohol/ester azeotropic systems was studied.The liquid-liquid equilibrium data of n-hexane/n-heptane-alcohol/ester-ILs system was determined,and the separation capacity of the ILs was analyzed.Taking 1-Hexyl-3-methylimidazolium tetrafluoroborate（[Hmim][BF₄]）as the extraction agent,the influence of temperature on the liquid-liquid phase behavior of the ternary system was investigated.The results showed that the influence of temperature on the phase equilibrium of the system was very small.For n-hexane-ethyl acetate azeotropic system,the extraction and separation of n-hexane-ethyl acetate by the four ILs were investigated.Longer side chain substituents of imidazole cation in the ionic liquid are more favorable for extraction.For n-heptane-n-butanol azeotropic system,the extraction and separation effects of four ILs on n-heptane-n-butanol system were studied.For the n-hexane-methanol azeotrope system,the selective extraction of n-hexane-methanol system by three ILs was investigated.The results showed that anion[HSO₄]^-has a stronger affinity for methanol than[OTf]^-,and disubstituted imidazole-ILs is more sensitive to the extraction and separation of n-hexane+methanol system than monosubstituted imidazole-ILs.Thermodynamic simulation was carried out for the eleven ILs systems studied.The liquid-liquid equilibrium data of n-hexane-ethyl acetate-ionic liquid system predicted by UNIFAC-Lei were compared with experimental data,then the prediction accuracy of UNIFAC-Lei model was evaluated.By correlating the experimental data using NRTL and UNIQUAC models,the model parameters of each system were obtained.The thermodynamic model can accurately describe the phase behavior of the system.This work providing basic data and theoretical reference for the application of ionic liquid extractant.