Direct synthesis of dimethyl carbonate from methanol and carbon dioxide over H_3PW_(12)O_(40)/Ce_xZr_(1-x)O_2 catalysts: Effect of acidity of the catalysts

摘要

-Ce_x-Zr_(1-x)O_2 catalysts were prepared by a sol-gel method, and H_3PW_(12)O_(40)/Ce_xZr_(1-x)O_2 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. NH_3-TPD experiments were carried out to investigate the effect of acidity on the catalytic performance of Ce_xZr_(1-x)O-2 and H_3PW_(12)O_(40)/Ce_xZr_(1-x)O_2. Catalytic performance of Ce_xZr_(1-x)O_2 and H_3PW_(12)O_(40)/Ce_xZ_(1-x)O_2 was closely related to the acidity of the catalysts. The amount of dimethyl carbonate produced over both Ce_xZ_(1-x)O_2 and H_3PW_(12)O_(40)Ce_xZr_(1-x)O_2 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_xZr_(1-x)O_2 and H_3PWW_(12)O_(40)/ Ce_xZr_(1-x)O-2in the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. Catalytic activity of H_3 PW_(12)O_(40)/Ce_xZr_(1-x)O_2 was higher than that of the corresponding Ce_xZr_(1-x)O_2 The enhanced catalytic performance of H, PW_(12)O_(40)/Ce_xZr_(1-x)O_2was attributed to the Brønsted acid sites provided by H_3PW_(12)O_(40).