Kinetic Study For Transesterification Of Ethylene Glycol With Methyl Acetate And Catalytic Reactive Distillation Simulation

The mixture of ethylene glycol,1,2-propylene glycol and 1,2-butanediol could be produced in many productive process in chemical industry.One of the most important source is the crude product of corn fermentative solution,which comes from the process of ethanol production by fermentation of corn,processed by dehydration,cracking and preliminary separation.The other is that the mixture of these three alcohols can be obtained in the process of producing ethylene glycol by coal.So the study of separation is a very important subject.Based on the method that mixed alcohols and methyl acetate undergoing transesterification,followed by separation and hydrolysis,and the starting point that preparing ethylene glycol diacetate,the kinetic behavior of ethylene glycol and methyl acetate was studied in this paper in order to provide basis for further distillation experiment and simulation.A preliminary simulation was carried out according to the experimental results.The DA330 ion exchange resin with better performance was selected as the final catalyst in three kinds of catalysts(DA330,Amberlyst 15 and D009).The effects of internal diffusion and external diffusion on the transesterification of ethylene glycol and methyl acetate were investigated.The experimental results show that the effect of external diffusion on the reaction can be excluded when the stirring rate reaches 300 r/min,and the effect of internal diffusion is considered ruled out because of the small impact of catalyst in the range of 0.5-2.0 mm on reaction.The effects of temperature,catalyst loading and molar ratio of alcohol to ester on the reaction were investigated on the basis of the foregoing.The results show that the two steps of the transesterification are endothermic reaction,and the reaction heat is small.The reaction equilibrium constant increases slightly with the increase of temperature.The reaction rate increases with the increase of catalystloading,and the reaction rate constant is linear with the ratio of initial catalyst addition to methyl acetate Rcat/MeAc.Increasing the proportion of methyl acetate in the feed can increase the conversion rate of EG and the yield of EGD.The experimental data were correlated with PH,LHHW,ER1 and ER2 models to obtain the parameters of each model using the least squares method and Runge Kutta method.The experimental values were in good agreement with the LHHW model by comparison.The activation energy and the pre exponential factor were calculated by the linear regression equation of Arrhenius equation,and the kinetic equation of the transesterification was obtained.The kinetic equation provides the necessary basic data for the simulation optimization and design of the subsequent catalytic distillation process.The RadFrac module of PLUS ASPEN was used to optimize the reactive distillation column based on the kinetic data.The optimal operating conditions are as follow: the number of theoretical plates of rectifying section,reaction section and stripping section were 10,24 and6 respectively;EG was fed from the upper part of reaction section and MeAc was fed from the lower part of the reaction section;reflux ratio was 0.8;mole ratio of alcohol to ester was 5:1.The EG conversion and the yield of EGD reached more than 99.6% under the conditions above.