Study On Separation Of Ethylene Glycol And 1,2-Butanediol By Azeotropic Distillation

To develop a process that coal replaces oil as raw materials to produce organic compounds has become the most important research filed in chemical industry with the shortage of petroleum resources.Ethylene glycol is an essential material of polyester industry,which has a great strategic significance for the coal chemistry.However,the reserves of coal resources are much larger than that of oil resources in our country.Therefore,to develop the production process of ethylene glycol in coal chemistry not only conforms to the conditions of coal reserves but also meets the demand of ethylene glycol for industry in our country.The main by-products of the production process of ethylene glycol in coal chemistry include 1,2-butanediol,1,2-propylene glycol,diethylene glycol and so on.The boiling point of 1,2-butanediol is very close to it of ethylene glycol in particular,which is very difficult to separate the mixed system of ethylene glycol and 1,2-butanediol by a common distillation.Therefore,the effectively removal of 1,2-butanediol from ethylene glycol has become the key factor for the production of ethylene glycol.In this paper,the binary mixture of ethylene glycol and 1,2-butanediol was taken as the research object.And the target of study is to find a solvent that can form azeotrope with 1,2-butanediol,which resolved the difficulty in the refining process of the production of ethylene glycol in coal chemistry.UNIFAC activity coefficient model was selected to calculate vapor-liquid equilibrium data and predicted azeotropic composition and azeotropic temperature.The solvent EGO was selected as the optimum solvent by the fuzzy comprehensive evaluation model,then the distillation experiment was done to verify it.The missing property parameters in Aspen software were supplemented according to the estimation results of group contribution method in this paper and the model accuracy was verified by the experimental data.It was developed to remove 1,2-butanediol by azeotropic distillation process that contained three distillation columns.The optimized operation parameters of distillation column showed it that the 1,2-butanediol can be effectively removed and the purity of ethylene glycol produced was more than 99.99%,in which the content of 1,2-butanediol was less than 60 ppm.Meanwhile,the mass fraction of by-product 1,2-butanediol can attain 99.9%.The yield of ethylene glycol and 1,2-butanediol were 99.99% and 97.68%,respectively.Besides,the consume of per ton ethylene glycol refined included 2.0 tons of low pressure steam,85.3 tons of cooling water and 0.03 kilograms fresh EGO.The process has advanced economic and technological indicators,which developed a new process for the refining process the production of ethylene glycol in coal chemistry.