Study On Catalysis Of Dimethyl Carbonate Prepared From Urea And Methanol

On the foundation of the present reviewed and analyzed progress of synthesis of dimethyl carbonate at home and abroad, the preparation of dimethyl carbonate from urea and methanol by catalysis is a new process and technology. The method can effectively reduce the cost of preparation of dimethyl carbonate because the material is facile and on the low side,and the pollution was hardly made in the prepared process. In this study, the prepared process was studied with a high-pressure reactor,the material of urea and methanol and catalysis of metal oxide. The standard heat of formation, free energy and heat capacity of dimethyl carbonate are calculated by the method of Benson's group contribution. A thermodynamic analysis of synthesis process of dimethyl carbonate by the method of urea alcoholysis was carried out with the emphasis on calculations of equilibrium constants. The optimum temperature conditions of reaction for preparation of dimethyl carbonate is 180 ℃. The study can provide the thermodynamic basis for the research of synthesis process of dimethyl carbonate and the development of catalysts thereof. Catalyst of metal oxide is studied for catalysis of the synthetical reaction of dimethyl carbonate. The experimental results indicate:Zinc oxide of single metal oxide has excellent catalytic activity in the suitable reaction,the yield of dimethyl carbonate is up to 12.37%( additive: methylate sodium ). Zinc oxide prepared by different methods has an order of catalytic activity: method Ⅲ> method Ⅱ> methodⅠ> method Ⅳ, the active order of single metal oxide is ZnO > PbO > MgO > CaO; Zinc oxide and lead oxide has excellent catalytic activity in the suitable reaction,the yield of dimethyl carbonate is up to 8.25%, the active order of binary metal oxide is ZnO-PbO > ZnO-CeO2 > ZnO-SnO2 > ZnCO3-La2O3 > ZnO-La2O3. The optimum reaction conditions: methylate sodium is 50mg, the reaction temperature is 180℃, the reaction time is 9h, molar ratio of methanol and urea is 36,weight fraction of catalyst is 6%. The regeneration and life of zinc oxide catalyst was studied by the experiments. The experimental results indicate: Catalytic activity of zinc oxide by a simple desiccation can't recycle, but by calcine can absolutely recycle. The life of zinc oxide catalyst is 12h. The experimental results make sure that the process of dimethyl carbonate prepared from urea and methanol is separated into two steps.