Study On The Effect Of Acetate-based Ionic Liquids On The Separation Process Of 2-butanone- Ethanol System

2-butanone and ethanol are important organic solvents and extensively used in the modern chemical industry.However,butanone and ethanol can form azeotropes at atmospheric pressure,and conventional distillation methods can not separate them from the mixture.Extractive distillation is a widely used separation method to separate azeotropics or close-boiling mixtures because of its advantages of low energy consumption,low corrosion,etc.In the process of extractive distillation,the most crucial step is to select effective entrainer.The traditional extractant has a series of problems such as environmental pollution,difficult recovery and large solvent loss.In recent years,ionic liquids(ILs)have drawn the attention as entrainer.Ionic liquids have many great physical and chemical properties.Therefore,the ionic liquid as an efficient extractant has important economic value and scientific significance.Ionic liquids were screened by COSMO-RS.10 cations and 10 anions were selected to separate 2-butanone-ethanol system.The results show that imidazole acetate has better separation.In order to compare the effect of different side chain lengths of cation on the separation efficiency of the system,three kinds of imidazolium-based ionic liquids were screened and synthesized:1-ethyl-3-methylimidazolium acetate([EMIM][Ac])and1-butyl-3-methylimidazolium acetate([BMIM][Ac]),1-hexyl-3-methylimidazolium acetate([HMIM][Ac]).And the three ionic liquids were analyzed by ~1H NMR,ion chromatography and water content respectively.The results show that the synthesized ionic liquid can meet the requirements of this experiment.Acetate-based ILs were selected as extractants for the separation of butanone-ethanol azeotrope.The Vapor-Liquid Equilibrium(VLE)data of binary(butanone-ethanol)and ternary systems were measured at atmospheric pressure.The results showed that all the three ILs azeotroped the system and significantly increased the relative volatility of2-butanone to ethanol.The separation effect of ionic liquids was:[EMIM][Ac]>[BMIM][Ac]>[HMIM][Ac];and using the NRTL model to fit the experimental data.The results show that there is a good correlation between binary and ternary VLE data and NRTL model.