Synthesis Of Dipheny Carbonate By Transesterification Of Phenol And Dimethyl Carbonate

In this paper, the reaction for preparing diphenyl carbonate (DPC), the key intermediate of the non-phosgene polycarbonate manufacturing process, by transesterification of dimethyl carbonate (DMC) with phenol in the presence of various catalysts including homogeneous and heterogeneous catalysts has been studied.The homogeneous synthesis of DPC has been investigated, especially using the Ti(OBu)4 as catalyst. The effect of each factor, such as temperature, time, amount of catalyst on reaction has been studied by orthogonal experiment. At the optimum condition, which is at normal pressure and temperature 175-185 ℃, in mole ratio of phenol to DMC of 3:1, in 2 weight percent of catalyst to DMC, in 9ml/h of DMC feed rate and for reation period of about 12 hours, the yield of DPC is 23.5%, methyl phenyl carbonate (MPC) yield is 47.89%, and the conversion of DMC is 82.4%. The reaction process was monitored and the reaction products were analyzied through gas chromatography and mass spectrograph. The byproduct butyl phenyl carbonate was firstly found. Catalyst Ti(OPh)4 was prepared and it is best suitable to avoid the byproduct butyl phenyl carbonate. In addition, the separating conditions and the revised factors of gas chromatography for analyzing reactant components were determined.A novel heterogeneous catalyst lead-ytterbium oxide has been prepared for the synthesis of DPC by transesterification of DMC with phenol. Compared with other double oxide based on lead, this catalyst is the best for the reaction. The effects of preparation method, calcinations temperature and molar ratio of Pb/Yb on the catalystic activity have been investigated. TPR and IR were employed for the catalyst characterization. Under the conditions of calcination temperature of 700 ℃ and Pb/Yb(mol)=2:l, mole ratio of phenol to DMC of 2:1, 10%(w) catalyst to DMC, reation temperature 160 ℃ for a period of 16 hours, the highest activity of catalyst was observed, the conversion of DMC is 56.87%, the yield of DPC is 17.1%, andMPC yield is 33.24%. At the same time, the reaction kinetics of MPC and DPC was studied.The transesterfication of DMC and phenol has been studied in a continuous gas-solid reactor at a range of temperatures 200-250℃ and space speed 1600 h-1. Sn(OBu)2 or Ti(OBu)4 supported on SiO2 are taken as catalyst, which were prepared by ourselves. The result shows this reaction is favorable for produce MPC, and the yield of MPC is above 6%, the selectivity is above 90% at one-period reaction. The effects of reaction temperature and the mechanism have been investigated. The more active catalyst and the more suitable carrier should be selected further not only to heighten the yield of MPC and DPC,but to avoid the production of anisole at above 250℃.