A new heterogeneous catalyst, lead-zinc double oxide, was prepared for the synthesis of diphenyl carbonate (DPC) by transesterification of dimethyl carbonate (DMC) and phenol. Usually, the reaction is carried out in the liquid phase using homogeneous catalysts such as organic Sri compound or Ti compound. Lead-zinc double oxide can overcome the shortages of homogenous catalysts and it is an active and selective catalyst for the reaction. The catalyst samples were prepared by two methods of co-precipitation and mechanical milling. In coprecipitation, three aqueous solutions, Pb(NO3)(2), Zn(NO3)(2) and NH3 . H2O, were added into a beaker simultaneously, then aged, filtrated, dried and calcined. In mechanical milling, lead hydrate and zinc hydrate were prepared separately, then mixed at some ration and calcined. The activity of single lead oxide or single zinc oxide was studied. The different conditions of preparation for lead-zinc double oxide, for example, molar ratio of Pb/Zn, calcination temperature and precursor, were investigated. The catalyst sample prepared by co-precipitation had high activity when n(Pb)/n(Zn) ratio was 2, Pb(NO3)(2) and Zn(NO3)(2) as precursors, and calcination temperature was 500 degreesC, and DPC yield was 44.8%. DPC yield achieved 45.6% over the catalyst sample prepared by mechanical milling. XRD, TPR and atomic absorption spectroscopy were employed for catalyst characterization. Pb3O4 was found as the main active phase, and amorphous ZnO as promoter. The reusability of the catalyst and the reason of deactivation were also studied.
