Studies On Synthesis Of Diphenyl Carbonate And Methyl Phenyl Carbonate By Transesterification

Diphenyl carbonate (DPC) is an important precursor for the synthesis of polycarbonate without using phosgene, and the transesterification of dimethyl carbonate(DMC) with phenol is considered to be the most promising process. The transesterification of DMC and phenol for diphenyl carbonate and methyl phenyl carbonate(MPC) synthesis has been studied in this thesis.In heterogeneous catalysts screening experiments, V₂O₅ showed good performance in the transesterification of DMC with phenol. The conversion of phenol could reach 34.6%, and the total selectivity and yield of MPC and DPC could be up to 98.8% and 34.2% respectively, under the reaction conditions of n(DMC)/n(PhOH) = 1, n(V₂O₅)/n(PhOH) = 0.04, T = 165¹80℃, t = 10 h. In addition, the result indicated V₂O₅ modified with TiO₂ exihibited better catalytic properties, and V₂O₅/TiO₂ catalyst could be separated from the reaction materials more easily than V₂O₅ catalyst.Using V₂O₅/TiO₂(n(V)/n(Ti) = 1) catalysis, the experimental conditions of transesterif- fication such as reactant ratio, catalyst amount, and reaction time were optimised. When the reaction had been carried out for 9 h at reaction temperature 165¹80℃, molar ratio of phenol to DMC 2:1, and catalyst amount 4.5%(wt), the conversion of phenol reached 27.9%, and the yield of DPC and the transesterification selectivity reached 24.4% and 99.7% respectively.Methyl phenyl carbonate was prepared by transesterification of DMC and phenol and the structure of the product was identified to be MPC by IR, UV, 1HNMR, GC-MS spectra. This proved that the synthesis of DPC was usually performed in two-step reaction module. In the first step, phenol is converted into methyl phenyl carbonate (MPC), and in the second step, MPC is converted into DPC by the reaction with phenol or by disproportionation.In addition, the constant-volume combustion heat(â–³cU) of MPC was determined as -25432.72 J·g^-1 by a oxygen bomb calorimeter at 298.15 K, and its standard molar combustion enthalpy (â–³cHmθ) and standard molar enthalpy of formation (â–³fHmθ) were calculated as -3868.92 kJ·mol^-1 and -422.33 kJ·mol^-1, respectively. Furthermore, the disproportionation of MPC into DPC under atmospheric-vacuum condition was studied. The results showed the disproportionation conversion of MPC could increase dramatically under vacuum condition and decrease the time of the reaction obviously at the same time. Under the reaction conditions of 600 mmHg, t = 5 h, the conversion of MPC was 63.0%. But the conversion of MPC was 49.1% when the reaction had been carried out for 15 h at normal atmosphere.