Synthesis of Diethyl Oxalate by Catalysis of Rare Earth Composite Solid Superacid under Microwave Radiation

Diethyl oxalate was synthesized with the catalyst of rare earth composite solid superacid SO42——TiO2-La3+ accelerated by microwave irradiation.Effects of molar ratio of ethanol to oxalic acid,microwave power,microwave irradiation time and catalyst dosage on esterification reaction were investigated by using orthogonal design method and single factor experimentation.The results showed that rare earth composite solid superacid SO42——TiO2-La3+ was an excellent catalyst for synthesizing diethyl oxalate.If the dosage of oxalic acid was 0.1mol,molar ratio of ethanol to oxalic acid was 3.2∶1.0,microwave power was 450W,microwave irradiation time was 12min,the quantity of catalyst was equal to 1.2% by mass of the total feed stock.Under these optimum experimental conditions,the esterification ratio was more than 97%,moreover,the catalyst could be repeatedly used six times without lossing its catalytic activity.The product was colorless and transparent.The product was verified by refractive index testing and IR spectrometry.