Separation And Purification Of Products In Transesterification Of Dimethyl Carbonate And Phenol

Diphenylcarbonate(DPC) is an important carbonic ester that has caused the great interest among researchers for its a number of applications. In synthesis paths for DPC, the transesterification of dimethyl carbonate(DMC) with phenol is thought to be the best one due to the use of nontoxic feedstock, no hazard to environment, and high conversion. Not only the high conversion of DPC, but more importantly, the yield of DPC is the key in industrialized operation. Therefor, related research of separation and purification of products in transesterification of DMC and phenol is important and is stdied in this work.According to the result of analyzing by GC-MS, the products of transesterification of DMC and phenol consist of dimethyl carbonate(DMC),anisole(AN),phenol(PhOH),methyl phenyl carbonate(MPC) and DPC. We propound a scheme according to the physical characters and experiments of these components. Most of impurities with low boiling point could be separated from filfrate by distillation under reduced pressure in the first time, then by means of recrystallization in hot ethanol to get pure DPC.The separation of each component is studied by distillation under reduced pressure. The experiments reveal that it can be separated effectively in the certain pressure and temperature. When the pressure of system is 20 mmHg, the contant of PhOH in the distillate is 94.63 %, while the pressure is 10– 5 mmHg, MPC is separated. The contant of DPC in the crude is 93.6 %. The yield is 64.5 % after recrystallization in ethanol. It saves much time and energy. When the pressure of system is 20-17 mmHg, the contant of PhOH in the distillate is 99 % by using rectifying equipment. It is better than the former. Finally, selection solvents for the recrystallization of diphenyl carbonate has been studied. It was found that ethanol was the optimal solvent, the solubility of diphenyl carbonate (DPC) in ethanol changed slowly in the recrystallization temperature range between 5.0℃and 15.0℃. The yield of DPC was as high as 89.0 % at the recrystallization temperature of 15.0℃. It was also found that the yield of DPC could be obviously improved in the case of mixed solvents of water and ethanol used as the recrystallization solvent. The yield of DPC was higher than 93.0 % and the purity of product was 99.6 % when the content of water varied between 25.0 % and 35.0 %.The method of separation and purification of products in transesterification of DMC and phenol in this dissertation will be usefull for the industrialized operation of DPC.