| Both dimethyl carbonate and ethanol are extremely important organic chemical raw materials,and have wide application in industrial production.The azeotrope formed by dimethyl carbonate and ethanol is a typical binary azeotrope system which cannot be separated by conventional methods.In recent years,ionic liquids,as a green,environmentally friendly solvent with unique properties such as unmeasurable vapor pressure,non-toxicity,non-corrosiveness,and recyclability,are replacing new organic solvents as extractive distillation.The trend of extractant,so the ionic liquid was used as the extractant for separating dimethyl carbonate and ethanol azeotrope,and the effect of ionic liquid on the phase equilibrium of dimethyl carbonate-ethanol system was studied.The paper uses COSMO-therm X computer software to explore the effect of different ionic liquids on the separation of azeotrope dimethyl carbonate-ethanol.675 ionic liquids of25 anions and 27 cations were selected to predict the selectivity of different ionic liquids.Selective ionic liquids were selected by selective analysis,and the economic cost and nature comparison of synthetic methods were combined.,1-but-3-methylimidazolium dibutyl phosphate([BMIM] [DBP])and 1-octyl-3-methylimidazolium acetate([OMIM] [OAc])were selected as the present The ionic liquid used in the experiment.The selected [BMIM] [DBP] was synthesized by consulting a large number of literatures,and [OMIM][OAc] was purchased.Two kinds of ionic liquids,and characterize the structure and composition of [BMIM] [DBP].By analyzing the results,it can be found that the [BMIM][DBP] prepared in the laboratory satisfies this experiment.Various requirements;experimental part,at 101.3 k Pa,measured the dimethyl carbonate-ethanol binary system,ternary system containing ionic liquid(dimethyl carbonate-ethanol + [BMIM] [DBP] /[OMIM [OAc])gas-liquid phase equilibrium data,observe the different experimental results corresponding to the two ionic liquids,the results show that the addition of two ionic liquids in the system,the system has a co-boiling point offset or even disappear,carbonic acid The relative volatility of dimethyl ester to ethanol was significantly improved,and the salting out effect was produced.When the content of the two ionic liquids increased to 0.1,the azeotropy of the system was eliminated,and the separation effect showed that [OMIM][OAc] was better.Using the NRTL activity coefficient model,the Levenberg-Marquardt method regresses the model values from the experimental data to minimize the objective function.The deviation between the model correlation value and the experimental value is less than 1%,indicating that the NRTL model is suitable for the ternary system containing ionic liquids.The NRTL model was used to predict the minimum mole fraction of the two ionic liquids required tobreak the azeotropy of the system.The results were:[BMIM][DBP]=0.087;[OMIM][OAc]=0.067,[OMIM][OAc] became the separated carbonate The methyl ester-ethanol azeotrope is the best extractant.Using the Aspen plus software,the ionic liquid [OMIM][OAc] with relatively good experimental results was selected,and the interaction parameters obtained by correlating the experimental data with the NRTL model were used to simulate the rectification process.The results show that the solvent ratio of the extractive distillation column is 0.29,the theoretical plate number of the whole tower is 35,the reflux ratio is 0.5,and the ionic liquid and raw material feeding positions are the third and the 14 th tray respectively,and the top product is dimethyl carbonate.The mass fraction of the ester can reach more than 99.5%,which meets the separation requirements.It is indicated that [OMIM][OAc] has an industrial prospect as an extractant for separating a dimethyl carbonate-ethanol azeotrope system. |
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