Effect Of Ionic Liquids On The Volatility Of Organic Solvents

In the extractive distillation,organic solvents often play the role of extracting agents,but due to their high volatility and have potential to pollute the environment,the use of these types of solvents has been gradually eliminated.Because of its high boiling point,strong stability,very low vapor pressure,near-non-volatile at room temperature,liquid is found to be an environmentally friendly solution.It is very suitable as extracting agent to replace the common organic solvents in the process of extractive distillation.A very general method used in laboratories is the study of vapor-liquid equilibrium on the effect of extractive distillation,so to explore the two-phase and three-phase vapor-liquid equilibrium of the ionic liquids on the organic solvents plays an important role to improve the effects of extractive distillation.Based on the literature,ionic liquids were produced for phase equilibrium studies,namely 1-methyl-3-methylimidazolium dimethyl phosphate[MMIM][DMP]was prepared by one-step method,1-ethyl-3-methylimidazolium thiocyanide[EMIM][SCN],1-butyl-3-methy limidazolium thiocyanate[BMIM][SCN]and 1-butyl-3-methyl tetrafluoroborate[BMIM][BF4],were prepared by two-step method.The binary vapor-liquid phase equilibrium data of ionic liquids for organic solvents at atmospheric pressure were measured by the CE-2 vapor-liquid equilibrium analyzer.The volatile effects of[MMIM][DMP]on 13 kinds of solvents were investigated,including water,alcoholic organic solvents(methanol,ethanol,isopropanol),esters(methyl acetate,ethyl acetate,dimethyl carbonate),acetonitrile,tetrahydrofuran,butanone,benzene,cyclohexane,and cyclohexene.The separation of benzene-cyclohexane,benzene-cyclohexene and cyclohexane-cyclohexene at atmospheric pressure,the[EMIM][SCN]and[BMIM][SCN]have been experimentally determined,and meanwhile,compared when the anions were the same,and the different influence of the length of imidazolium cation side chain on the azeotropic system.The thermodynamic model of electrolyte-regular,two-liquid(e-NRTL)was used to correlate the measured vapor-liquid equilibrium data,and the deviations of the experimental and calculated values were analyzed.The results showed that the thermodynamic model is suitable and the experiment is accurate.[EMIM][SCN]and[BMIM][SCN]have separation effects on three azeotropic systems.