Study On Lead-Zinc Double Oxide Deactivation And Supported Liquid Phase Catalysts In Synthesis Of Diphenyl Carbonate By Transesterification

The reason of lead-zinc double oxide deactivation and supported liquid phase catalysts (SLPC) in synthesis of diphenyl carbonate (DPC) by transesterification of phenol and dimethyl carbonate (DMC) have been studied.The reason of lead-zinc double oxide deactivation has been analysed by XRD, XPS, IR, atomic absorption spectroscopy, elemental analysis and TG. Results show that, Pb4O(OC6H5)6 is formed through the reaction of phenol and lead in the catalyst during the transesterification reaction, which leads to the crystal phase change of active component ( PbO and Pb3O4 crystal phase disappears) and serious leaching of lead. What is more, the leached lead is in the form of a mixture of Pb4O(OC6H5)6 and PbO, whose weight percentage is 62.7% and 37.3%, respectively.Pb4O(OC6H5)6 , which is formed by the reaction of phenol and PbO, also has catalytic performance for the transesterification reaction. When the quantity of Pb4O(OC6H5)6 is 13.3 wt%, the highest yield of DPC is 17.2%.When the leached lead compound is recovered and reused in the transesterification of phenol and DMC for three times, the yield of DPC is approximately stabilized in 18%.The catalytic performance of SLPC in synthesis of DPC by transesterification has been studied, and the suitable conditions to prepare SLPC have been dertimined. When AC as support, squalane as liquid phase, n-Bu2SnO as active compoent, preparation method is one step, the loading quantity of squalane and n-Bu2SnO are 20.0% and 10.0% respectively, SLPC has the best catalytic performance, and the highest yield of DPC is 19.3%, which is 12.2% higher than over n-Bu2SnO/ AC.The lead-zinc double oxide is modified by La2O3. The catalytic performance of lead-zinc-lanthanum composite oxide has been studied. Results show that, when the mole ratio of Pb, Zn and La is 1:0.8:0.2, the catalytic performance is better, and the highest yield of DPC is 35.2%. But the proplem of lead leaching is not resolved with the adding of lanthanum.Pb-MCM-41 mesoporous molecular sieves has been synthesized by using in situ method and incipient impregnation method. The catalytic performance of Pb-MCM-41 has been studied preliminarily.