Isobaric Vapor-liquid Equilibrium For Ternary System Of Ethanol,Ethyl Propionate And Para-Xylene System

Ethyl propionate is a kind of widely-used organic synthetic raw material and solvent.In traditional industry,the method of producing ethyl propionate is esterification of propanoic acid and ethanol at atmospheric pressure.However,ethyl propionate and ethanol can form an azeotrope at atmospheric pressure.Highly purified ethyl propionate cannot be obtained by ordinary distillation,so it is necessary to use special distillation to separate mixtures.According to the principle of “like dissolves like” and the evaluation principles of choosing extraction agent,some solvents were selected to separate the azeotrope of ethanol + ethyl propionate after the qualitative selection.And infinite dilution activity coefficient was calculated by COSMO-SAC model to confirm that para-xylene is the most suitable extractant.Due to wide availibility,low cost,less causticity,good thermal stability and miscibility with organic solvent,para-xylene has been applied as an effective additive in extractive distillation.The study of the influence of para-xylene as an extractant on the system of ethanol + ethyl propionate was made in this paper.Isobaric vapor-liquid equilibrium(VLE)data for the binary system of ethyl propionate + para-xylene and the ternary system of ethanol + ethyl propionate + para-xylene at 101.3 kPa were determined by a modified Othmer still.The experimental data of the binary system were checked by the Van Ness test and Wisniak thermodynamic consistency test,and the result showed the reliability of the experimental data.The VLE data of ternary system of ethanol + ethyl propionate + para-xylene indicated that para-xylene breaks the azeotrope binary mixture of ethanol + ethyl propionate when the mole ratio of para-xylene is 10%.The relative volatility of ethanol to ethyl propionate rises when the content of para-xylene increases.To acquire the binary interaction parameters,the binary experimental data were correlated with Wilson and UNIQUAC models and the VLE data of the ternary system was predicted.The maximum average relative deviations of equilibrium temperature and vapor-phase mole fraction by Wilson model were 0.16% and 3.4321%,respectively.The maximum average relative deviations of equilibrium temperature and vapor-phase mole fraction by UNIQUAC model were 0.13% and 3.1048%,respectively.The results revealed that both Wilson model and UNIQUAC model can be well correlated for the ternary system of ethanol + ethyl propionate + para-xylene.The process of continuous extractive distillation for the ternary system of ethanol + ethyl propionate + para-xylene was simulated by Aspen Plus.The effects of feed location of crude and solvent,reflux ratio,solvent ratio on product purity were investigated,and the proper process parameters were obtained.