Catalytic properties and structure of zirconia catalysts for direct synthesis of dimethyl carbonate from methanol and carbon dioxide

Selective synthesis of dimethyl carbonate from methanol and CO₂ proceeded effectively on a zirconia catalyst prepared by the calcination of zirconium hydroxide at 673 K. The bulk of this zirconia had a mainly tetragonal structure which was determined by XRD. In contrast, near its surface the monoclinic phase was major and the tetragonal phase was minor, as determined by laser Raman spectroscopy. But the ratio of the tetragonal phase to the monoclinic was higher on this zirconia catalyst than on other catalysts prepared at different calcination temperatures. The number of neighboring acid-base sites estimated by temperature-programmed desorption is suggested to be related to the activity of dimethyl carbonate formation.