Preparation Of La_0.5Pb_0.5MnO₃ Oxide Support By Microwave Sintering And Application For Synthesis Of Diphenyl Carbonate

Diphenyl carbonate (DPC) is one of the important chemical intermediates for polycarbonate (PC) in plastics industry by Non-Phosgene Method. Oxidative carbonylation of phenol for synthesis of DPC take phenol,CO,O2 as the raw materials. This method is the most valuable industrial route because of the following advantages: cheap raw materials, one-step synthesis and high atom utilization. At present, the study mainly concentrates on preparing a novel heterogeneous catalytic system with excellent catalytic properties, and the core is how to reduce the industial costs.A supported Pd catalytic system with high activity that uses La_0.5Pb_0.5MnO₃ oxide as support has been prepared by our research group. In the current, common methods of perovskite type oxides preparing , such as solid state reaction, sol-gel and rotating packed bed(RPB), needs high-temperature for the precursor sintering in post-processing in which have high energy consumption and industial costs. Compared with the tradional sintering methods, microwave sintering of its unique heating method, can significantly reduce energy consumption and industrial costs for the preparation.In this article, the precursor of La_0.5Pb_0.5MnO₃ oxide was prepared by solid state reaction, sol-gel and RPB methods. Then the La_0.5Pb_0.5MnO₃ support was prepared by microwave sintering. The effects of different microwave sintering power and times on properties of La_0.5Pb_0.5MnO₃ powder were investigated in combination with XRD, BET, SEM and WJL techniques, and the effects of reaction temperature, pressure, time were discussed in the batch slurry reactor through the synthesis of DPC. The main conclusions are as follows:(1) The perovskite-type composite oxide La_0.5Pb_0.5MnO₃ support was successfully synthesized by microwave sintering with the precursor prepared by solid state reaction, sol-gel and rotating packed bed(RPB).(2) The optimum preparation conditions of La_0.5Pb_0.5MnO₃ support by solid state reaction-microwave sintering method with MnCO₃,PbCO₃,La₂O₃ are under the conditrion of microwave sintering power: 450W, and time: 5min. The corresponding catalyst shows the highest activity, the yield of DPC is 7.5%.(3) The optimum preparation conditions of La_0.5Pb_0.5MnO₃ support by sol-gel-microwave sintering method with La,Pb,Mn nitrate and citric acid are under the conditrion of microwave sintering power:450W,and time:15min. The corresponding catalyst shows the highest activity, the yield of DPC is 8.2%.(4) The optimum preparation conditions of La_0.5Pb_0.5MnO₃ support by RPB- microwave sintering method with La,Pb,Mn nitrate and NaOH solution are under the conditrion of microwave sintering power:450W,and time:5min. The corresponding catalyst shows the highest activity, the yield of DPC is 10.2%.(5) Compared with the tradional sintering methods, the yield of DPC decreased by 0.9% and 1.5% through the catalyst prepared by sol-gel-microwave sintering and RPB- microwave sintering methods. However,the sintering time drops from a few hours to a few minutes substantially. Microwave sintering is conducive to industrial production which can reduce the reaction energy and save the industrial costs greatiy.(6) The suitable reaction conditions for RPB-microwave sintering catalyst are reaction total pressure 5.1MPa, reaction time 6h and reaction temperature 65℃. The yield of DPC is 14.6%.