Dibutyl Oxalate Preparated By Transesterification

Dibutyl oxalate is an important chemical and commonly synthesized by esterification,but it has not been reported by transesterification.In this paper,dimethyl oxalate and n-butan alcohol as raw materials,methanol sodium as a catalyst,transesterification method for the synthesis of dibutyl oxalate.The catalyst dosage of the reaction was studied by intermittent reaction,the effect of material ratio and reaction temperature on the conversion rate of dimethyl oxalate,and on the basis of intermittent reaction,further studied the conversion rate of dimethyl oxalate and the yield of dibutyl oxalate after breaking thermodynamic equilibrium limit by reactive distillation,The results of reactive distillation synthesis under different proportioning conditions were investigated.In this paper,the thermodynamic analysis of the reaction system of dimethyl oxalate and n-butan alcohol are studied firstly.The difficulty degree and the equilibrium conversion rate of the reaction were determined by theoretical calculation,and the process of the reaction was determined according to the calculation results.At the same time,the equilibrium constants at different reaction temperatures are measured.According to Van ' t Hoff equal pressure equation,the relation between the equilibrium constants of each step and the temperature is obtained,the data of each step reaction heat is calculated,and the experimental results are compared with the theoretical calculation results.The result show's that the error of the theoretical calculation is very large,can not to guide the actual synthesis process.The reason is that a lot of basic data of dimethyl oxalate,methyl butyl oxalate and dibutyl oxalate are lacking,too much use of group contribution method to estimate the basic physical property by the theoretical calculation.Resulting to the calculation results deviate from the actual situation.The size of the reaction equilibrium constants obtained from the experimental results shows that the reaction steps are endothermic,the disproportionation of methyl butyl oxalate and the further reaction of methyl butyl oxalate with n-butan alcohol are all reaction processes.In the batch reaction experiment,when the catalyst dosage is 1.0%(the quality of dimethyl oxalate is measured),the catalyst dosage is the most economical.Because the degree of reaction is limited by the mechanical equilibrium of the heat,too much alcohol and ester ratio,can not obtain a satisfactory result.Under the condition of the most economical catalyst dosage 1.0%,a reactive distillation experiment is conducted to break the equilibrium limit of thermodynamic reaction,and the experiment of nbutan alcohol and dimethyl oxalate under different molar ratios are carried out.When the molar ratio of the materials was 3:1,dimethyl oxalate was completely transformed and the yield of dibutyl oxalate is 98.9%.According to the above studies,dimethyl oxalate and n-butan alcohol as raw materials,methanol sodium as a catalyst,transesterification synthesis of dibutyl oxalate reaction to the thermodynamic equilibrium reaction,the reaction process endothermic.By means of reactive distillation to break the thermodynamic equilibrium limit,when the catalyst dosage is 1.0% of the quality of dimethyl oxalate,n-butan alcohol and dimethyl oxalate molar ratio is 3:1,the conversion rate of dimethyl oxalate is close to 100%,the yield of dibutyl oxalate reached 98.9%,and the synthetic experiment achieves more satisfactory results.