Preparation of Solid Superacid SO42-/ZnO-TiO2 and Its Action on Synthesis of Dimethyl Carbonate from Urea and Methanol

SO42-/ZnO-TiO2 catalyst was prepared by sulfating ZnO-TiO2 powders with H2SO4 solution. The catalyst was characterized by XRD, IR and Hammett indicator. The catalyst showed strong acidity(H0 ≦-16.0). The optimum conditions are found that the calcination temperature is 823K and the soaked consistency of H2SO4 is 1 mol/dm3. Then SO42-/ZnO-TiO2 was applied as the catalyst in the catalytic synthesis of dimethyl carbonate(DMC) from urea and methanol under the optimum conditions and revealed higher catalytic activity. On condition that the reaction time is 6h, the reaction temperature is 433K, the mass percent of the catalyst used in the reactants is 5wt.%, and the molar ratio of methanol to urea is 14, the yields of DMC can reach 27.9%.