Preparation Of La_0.5Pb₀₅MnO₃Powder By Rotating Packed Bed And Its Application In Synthesis Of Diphenyl Carbonate

Diphenyl carbonate （DPC） is an important precursor for polycarbonate（PC） in plastics industry. In the current research for environmentally benignand sustainable processes, oxidative carbonylation of phenol for synthesis ofDPC attracts much attention because of the following advantages: nophosgene and one-step synthesis. The study mainly focused on seeking anovel heterogeneous catalytic system with high efficiency and high selection.A supported Pd system with perovskite-type La_0.5Pb₀₅MnO₃oxide assupport has been developed by our research group. The results show that thecatalyst has high activity, but due to high Pd content on catalyst and prettyhigh O2pressure for DPC synthesis, the current preparation method is not suitto industrialize. Compared with normal materials, nanometer materials ascatalyst or supports could improve catalytic efficiency and lower Pd contentbecause of smaller particle size, better electronic property and adsorptioncharacter. Therefore, in this paper, rotating packed bed（RPB）, which cangreatly strengthen the process of micro-mixing, was selected to preparenanometer perovskite-type La_0.5Pb₀₅MnO₃oxide.The precursor of La_0.5Pb₀₅MnO₃oxide was prepared with La（NO3）3,Pb（NO3）2, Mn（NO3）2and NaOH by co-precipitation method in RPB, Theeffects of rotating speed of RPB, flow rates of reactants and the addition ofsurfactants on properties of La_0.5Pb₀₅MnO₃powder were investigated incombination with XRD, BET, TEM and SEM techniques. The mainconclusions are as follows:（1） The optimum preparation conditions of La_0.5Pb₀₅MnO₃support bytraditional co-precipitation method are0.03mol/L nitrate,0.2mol/LNaOH,aging time5h,calcination at650℃for2h. The highest yield of DPC of thecatalyst is10.1%. （2） The steric effect of PEG as dispersing agent can enhance thedispersion and specific surface area of supports, which causes the incrementof the yield of DPC. The specific surface of supports and yield of DPCreach48.5m²/g and12.30%, respectively.（3） Based on the co-precipitation method, the single phaseLa_0.5Pb₀₅MnO₃perovskite can be prepared by RPB at rotating speed of1000r/min with the reactants flowing rate of60L/h.（4） Both the rotating speed and flow rates have significant influence onthe activity of catalyst. At rotating speed of1200r/min, flowing rate of60L/h,the yield of DPC reaches11.31%.（5） After the addition of PEG in the optimal conditions, i.e.,10000inmolecular weight and0.0015mol/L in amount, the specific surface area ofsupport and yield of DPC reach53.73m²/g and13.30%, respectively. Theparticle size of support is in the range of20-35nm.（6） The catalysts prepared by RPB had good stability and repetition.（7） The suitable reaction conditions is the loading amount of Pd0.5%,reaction temperature65℃, reactiontotal pressure5MPa,6%O2and reactiontime9h. The yield of DPC reaches21.90%.