Direct synthesis of dimethyl carbonate from methanol and carbon dioxide over H3PW12O40/CeXZr1?XO2 catalysts: Effect of acidity of the catalysts

Ce _X Zr_1−X O₂ catalysts were prepared by a sol-gel method, and H₃PW₁₂O₄₀/Ce _X Zr_1−X O₂ catalysts were then prepared by an impregnation method. Both catalysts were applied to the direct synthesis of dimethyl carbonate from methanol and carbon dioxide in a batch reactor. NH₃-TPD experiments were carried out to investigate the effect of acidity on the catalytic performance of Ce _X Zr_1−X O₂ and H₃PW₁₂O₄₀/Ce _X Zr_1−X O₂. Catalytic performance of Ce _X Zr_1−X O₂ and H₃PW₁₂O₄₀/Ce _X Zr_1−X O₂ was closely related to the acidity of the catalysts. The amount of dimethyl carbonate produced over both Ce _X Zr_1−X O₂ and H₃PW₁₂O₄₀/Ce _X Zr_1−X O₂ catalysts increased with increasing acidity of the catalysts. This indicates that acidity of the catalyst played a key role in determining the catalytic performance of Ce _X Zr_1−X O₂ and H₃PW₁₂O₄₀/Ce _X Zr_1−X O₂ in the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. Catalytic activity of H₃ PW₁₂O₄₀/Ce _X Zr_1−X O₂ was higher than that of the corresponding Ce _X Zr_1−X O₂. The enhanced catalytic performance of H₃ PW₁₂O₄₀/Ce _X Zr_1−X O₂ was attributed to the Br?nsted acid sites provided by H₃PW₁₂O₄₀.