A series of catalysts were studied for the synthesis of diphenyl carbonate(DPC)by transesterification of dimethyl carbonate(DMC)with phenol.It was found that V-Cu oxide was the best catalyst among the tested catalysts.The effects of V-Cu amount,molar ratio of copper to vanadium,molar ratio of dimethyl carbonate to phenol and reaction time were investigated.Under the conditions of catalyst amount 3.1%(mass ratio to phenol),molar ratio of Cu/V of 1∶4,molar ratio of DMC/phenol of 1.5∶1 and a reaction time 9 h,the maximum conversion of phenol and total yields of methyl phenyl carbonate(MPC)and DPC were 41.9% and 40.3%,respectively.Reuse of the catalyst revealed that V-Cu oxide was a relatively stable catalyst.The activity of the catalyst after being reused four times reduced from 41.9% to 29.1%.Moreover,the deactivated catalyst was easily regenerated by calcination in air,and the catalytic activity of the regenerated catalyst was almost as high as that of the fresh sample,the phenol conversion was 39.8%.
The reaction between ethylene carbonate and dimethyl terephthalate was carried out for the simultaneous synthesis of dimethyl carbonate and poly(ethylene terephthalate). This reaction is an excellent chemical process that is environmentally friendly and produces no poisonous substance. The metal acetate catalysts used for this reaction are discussed in detail. Lithium acetate dihydrate was found to be a novel and efficient catalyst for this reaction. Compared with other metal acetates, lithium acetate dihydrate can attain a maximum catalytic activity at a lower concentration. When the reaction was carried out under the following conditions: the reaction temperature from 230 to 250 ℃, molar ratio of ethylene carbonate(EC) to dimethyl terephthalate(DMT) 3[DK]∶1, reaction time 3 h, and a catalyst amount of 0.4%(molar fraction to DMT), the yield of dimethyl carbonate(DMC) was 79.1%.
