Synthesis Of Environmental Friendly Plasticizer Diethylene Glycol Dibenzoate By Reactive Distillation

With the rapid development of the plasticizer industry,seeking non-toxic and environmental friendly plasticizers that can replace phthalate esters has become a research hotspot in industry and academic.Diethylene glycol dibenzoate(DEDB)is a kind of safe,non-toxic and environment-friendly plasticizer which has attracted extensive attention due to its good compatibility and excellent plasticizing performance,having a very broad application prospects.In this paper,octyl benzoate with high purity was synthesized from benzoic acid and the reaction kinetics of transesterification of octyl benzoate with diethylene glycol(DEG)for DEDB was studied.The reactive distillation process of the transesterification reaction was simulated in Aspen Plus,which provided theoretical basis for industrial design.Firstly,tetrabutyl titanate was selected to catalyze the esterification of benzoic acid with n-octanol for octyl benzoate,with the effect of reaction temperature,reactants mole ratio and catalyst concentration investigated.After the determination of the optimum reaction conditions,Aspen Plus was used to simulate the process of distillation of crude octyl benzoate.Guided by the simulation results,the rectification was carried out in a batch distillation column and the octyl benzoate product with a purity of 99.3%was obtained,which could be used as raw material for the exploration of DEDB synthesis.Secondly,sodium methoxide was selected as the optimum catalyst for DEDB synthesis from octyl benzoate and DEG and the effect of catalyst concentration,reactants mole ratio and reaction temperature were investigated.The DEDB product synthesized under the optimal conditions was a light yellow transparent oily liquid with an acid value of 0.1866 mgKOH·g-1,and an ester content of 99.28%.The product met the quality index.With the conditions of transesterification reaction optimized,a homogeneous kinetic model was established and the model parameters were calculated,which provided basic data for the application of reactive distillation in the transesterification process.Finally,the process of reactive distillation for DEDB synthesis was simulated and optimized by Aspen Plus on the basis of kinetic data and thermodynamic data reported in literature.The RadFrac module,NRTL thermodynamic model and sensitivity analysis tool were applied in the simulation.The results showed that it was suitable to feed raw materials at the 8th theoretical plate.The appropriate mole ratio of octyl benzoate to DEG in the feed stream was 2:1.The optimal reflux ratio and the recovery ratio on the top of the column were 1 and 0.65,respectively.Under the conditions above,the product got from the top of the column was n-octanol with a mass fraction greater than 99%,which can be recycled for the synthesis of octyl benzoate,and the mass fraction of DEDB in the bottom product was 93%.The simulation results provide a theoretical reference for industrial design of DEDB synthesis by reactive distillation.