Study On The Synthesis Of Diphenyl Carbonate By The Transesterification Of Dimethyl Carbonate And Phenol

Diphenyl carbonate (DPC) is an environmentally benign intermediate for producing many organic compounds and polymer materials. The transesterification of dimethyl carbonate (DMC) and phenol to DPC is a promising non-phosgene process. In this thesis, the reaction process of DPC synthesis by the transesterification of DMC and phenol has been studied.The thermodynamic analysis for the transesterification of DMC and phenol was just reported by some patents on the technology process design and the data was not introduced in detail, which made it difficult to verify the the data. To understand the thermodynamic process of the transesterification, the thermodynamic properties (△r H o,△r S o,△r G o, K p ) of the reaction for production of DPC and anisole from 373 K to 473 K was calculated by using Material Studio and ChemCAD software as well as Benson and Joback group contribution methods. The results indicate that the transesterification is an endothermic reaction and the reaction equilibrium constant is low. Because the transesterification is thermodynamically unfavorable, it is necessary to remove byproduct methanol in time.Owing to lack of commercial methyl phenyl carbonate (MPC) standard sample, the intermediate MPC can't be quantified accurately. A new reation route was proposed and a high-purity sample (98.32%) of MPC was obtained by developing a novel reaction route followed by a series of separation and purification. Ethyl benzoate and acetone were separately used as the internal standards for quantitative analysis of the products and distillates by gas chromatography with OV-101 capillary column. With this standard method, simultaneous quantification of DMC, MPC, DPC, phenol and anisole can be achieved accurately, which provide the standard methods for evaluation of different catalysts and control of the reaction process. The microwave-aided catalytic technique was applied in the transesterification of DMC and phenol. Compared to conventional heating, the catalytic activities of traditional catalysts were improved greatly under microwave heating. The reaction condition of the transesterification catalyzed by Bu2SnO was optimized under microwave heating. By comparing the time process of the transesterification under different heating methods, the synthesis of DPC followed different reaction routes under microwave irradiation and conventional heating. DPC was synthesized by thetransesterification of DMC and phenol to MPC and MPC then reacted with phenol to DPC under microwave heating. Under conventional heating method DPC was obtained by the transesterification of DMC and phenol followed by the disproportionation of MPC into DPC. The mechanism of microwave accelerating transesterification was investigated: the improved DPC yield and reaction rate enhancement were due to the special heating effect of microwave irradiation.The mechanism for the transesterification in the presence of traditional catalysts showed the acid and basic sites performed catalytic activity respectively. The catalytic activity increased and the selectivity decreased as the acidity or basicity increased. The mechanism of DPC synthesis catalyzed by metal oxide loaded on different carriers indicated the weak acid active center cooperated with the weak base active center is favorable for the transesterification. The catalytic activity increased and selectivity decreased as the acidity or basicity increased.Lipase coated with epoxy propane modified surfactant showed high activity and selectivity for DPC synthesis by the transesterification in organic solvent. The effects of various operational conditions on the activity of surfactant-coated lipase for catalyzing the transesterification of DMC and phenol were investigated in detail. It was found that the didodecanyl glutamate ribitol amide with 4 epoxy propane is the best surfactant.The optimal pH for preparation of the coated lipase is 6.8 and the optimal reaction temperature is 35℃. The most suitable solvent is octane and the best molar ratio of DMC to phenol is 1:1. The deactivation rate constant kd of the modified coated-lipase in organic solvent is 0.1 h-1 and the stability enhanced one time.