Separation of ethyl formate and ethanol azeotrope by extractive distillation using phosphate salt ionic liquid as extractant
In the process of producing ethyl formate with formic acid and ethanol as raw materials,the unreacted ethanol and ethyl formate will form an azeotrope,which is difficult to separate.In this work,the method of extractive distillation is used to separate the ethyl formate-ethanol azeotrope system with the ionic liquid as an extractant.The ionic liquid is screened by the COSMO-RS model,and the ionic liquid is determined to be l-ethyl-3-methylimidazole diethyl phosphate([EMIM][DEP])and 1-butyl-3-methylimidazole diethyl phosphate([BMIM][DEP]).The vapor-liquid equilibrium(VLE)data of the ethyl formate+ethanol binary system and the ethyl formate+ethanol+ionic liquid ternary system are determined,and the experimental data are correlated with the NRTL model.Finally,the separation mechanism is explored by excess enthalpy analysis and σ-profile analysis(probability distribution of surface charge density).The results show that the relative volatility of ethyl formate increases with the increase in the molar fraction of two ionic liquids(ILs).When the ionic liquid concentration is 0.030,the relative volatility of ethyl formate to ethanol is greater than 1,and it can be seen that the separation effect of[EMIM][DEP]is better than that of[BMIM][DEP]ionic liquid.Through excessive enthalpy analysis,it is found that hydrogen bonds and van der Waals forces are more easily formed between ionic liquid and ethanol molecules,and the interaction between molecules is stronger than that between ionic liquid and ethyl formate,which promotes the separation of ethyl formate and ethanol.With the increase in ionic liquid concentration,the interaction between molecules is enhanced.Finally,the σ-profile analysis shows that ionic liquid is more inclined to interact with ethanol to separate ethyl formate,and it can be concluded that the shorter the cationic carbon chain of ionic liquid,the better the separation effect.
alcohol ester separationextractive distillationionic liquidCOSMO-RSNRTL model
万方数据
维普
