Surface structure and catalytic performance of CuCl/SiO2-Al2O3 catalysts for methanol oxidative carbonylation

Aluminum was doped into amorphous silica get to modify its surface structure. The obtained SiO2Al2O3 support was used to prepare the CuCl/SiO2-Al2O3 catalyst by solid-state ion exchange, and the catalyst activity for liquid-phase oxidative carbonylation of methanol to dimethyl carbonate was investigated. The results showed that the prepared SiO2-Al2O3 support kept the amorphous structure of the silica gel. The BET specific surface area of the silica gel was decreased to 200 m(2)/g, and the surface acid sites (including Bronsted acid sites) were increased. In the CuCl/SiO2-Al2O3 catalyst, CuCl was not only dispersed on surface but also was ion exchanged with surface Bronsted acid sites of the SiO2-Al2O3 support to form Cu+ species, which resulted in a decrease in BET specific surface area to 148 m(2)/g. These two kinds of Cu+ species on the catalyst surface were both active centers for the oxidative carbonylation of methanol to dimethyl carbonate. When the catalyst was prepared with Si/Al molar ratio of 5 and was calcined at 500 degrees C, the selectivity and space-time yield of dimethyl carbonate reached 74% and 1.27 g/(g(.)h), respectively.