Isobaric Vapor Liquid Equilibrium Of Benzene Ethanol System Containing Ionic Liquids

Benzene and ethanol are important raw materials in chemical production process,while benzene and ethanol exist in the form of azeotrope under atmospheric pressure.The distillation method can not been used to separate benzene from ethanol.Extraction distillation is a common method for azeotropic system separation,which is simple to operate and has less energy consumption.Ionic liquids have been widely studied as a new green extractant because of its low vapor pressure and designability.Based on this,the azeotropic system of benzene and ethanol was separated by using ionic liquid as extractant.The main research contents are as follows:(1)529 ionic liquids were obtained by random combination of 23 anions and 23 cations by cosmotherx software.According to the predicted solvent degree,selectivity results,the morphology and economic cost of ionic liquids,three target ionic liquids were selected,namely[N_4,4,4,1][Ac],[N_8,1,1,1][Ac],[N_4,4,4,1][Pr].(2)The gas-liquid equilibrium data of benzene ethanol binary system and benzene ethanol ionic liquid ternary system were measured at atmospheric pressure respectively,so as to analyze the separation effect of ionic liquid on benzene ethanol azeotropic system.The results show that the addition of three ionic liquids can increase the mole fraction of benzene in gas phase and produce salting out phenomenon.This phenomenon becomes more and more obvious with the increase of ionic liquid concentration,and finally breaks the azeotropic of benzene ethanol.Then,the NRTL model is used to correlate the experimental data and get the binary interaction parameters by regression.It shows that NRTL model is suitable for ternary system containing ionic liquids.The minimum mole fraction of the three ionic liquids[N_4,4,4,1][Ac],[N_8,1,1,1][Ac],[N_4,4,4,1][Pr]can be obtained by NRTL model,respectively,which are 0.0720,0.0706 and 0.0850.[N_8,1,1,1][Ac]as the best extractant for the separation of benzene ethanol azeotrope.(3)The best extraction agent[N_8,1,1,1][Ac]was selected to separate benzene ethanol azeotrope system.The process of separation of benzene ethanol by extraction distillation was simulated by ASPEN PLUS software.At the same time,the optimization results are as follows:the theoretical plate number of the whole column of the extraction distillation tower is 17,the feed position of raw material is the 12th tower plate,the feed position of the extractant is the second,the feed quantity of the extractant is 21kmol/h,and the reflux ratio is 0.6.Under the above process parameters,the purity of benzene at the top of the distillation column is 99.9%and the purity of ethanol is 99.9%,which provides a theoretical reference for the practical chemical operation of extractive distillation of benzene ethanol with ionic liquid.