Design And Control Of Dimethyl Carbonate-methanol Separation

Dimethyl carbonate is one of the best prospect green chemical products and had a wide future in chemical Industry.It can be used in carbonylation,methylation and carbomethorylation to replace the old highly toxic methyl chloride,phosgene and dimethyl sulfate which is widely used in old production process.In the DMC synthesis process,the most commonly used method is the transesterification and oxidation carbonylation.The product which is produced by both methods is low-purity and forms an azeotrope with methanol.The azeotrope boiling point is 63.7 ?at atmospheric pressure,and Me OH : DMC is 70wt%: 30wt% in the azeotrope.It is difficult to meet the requirements of high purity DMC products by conventional distillation technology.The purity of DMC is directly determines the benefits of the factory,so it is very important that the research for DMC-Me OH azeotrope separation process.At present,Low temperature crystallization,pressure swing distillation,azeotropic distillation and membrane separation processes is the main method for DMC-Me OH separation.The low temperature crystallization process is High energy consumption and Operational difficulties.The pressure swing distillation process means high equipment cost and high energy consumption.The membrane separation processes is still walking on the road to industrialization.Therefore,azeotropic distillation and extractive distillation process is the main methods of separation.The pressure swing distillation process uses the deviations of DMC-Me OH system on the Raoult's law,and using two different operating pressures in the process to make DMC and Me OH separation.The azeotropic distillation process is to add a new agent in the DMC-Me OH system,such as C5 ~ C8 alkane or cycloalkane,the new agent can form a new azeotrope with methanol,and the new azeotropic temperature is lower than the azeotropic temperature of the original azeotrope.The temperature difference of new azeotrope and original azeotrope is required greater than 10 ? for industrial production.The extractive Distillation process is to add a low volatility extractant which does not form a new azeotrope with the mixture.The extractant can significantly improve the relative volatility of original mixture,so that we can use the method to separate the azeotrope.The steady-state simulation of pressure swing distillation,azeotropic distillation and extractive distillation process are established by Aspen Plus to separation DMC-Me OH azeotrope system,and the lowest energy consumption is used to be optimization target.In the paper,the best method is selected in the three optimized process.The selected separation process is used to do dynamic control in the Aspen Dynamics.Finally,we get the process and control structure of DMC-Me OH separation.