Abstract: Chlorine-free CuO/AC, Cu2O/AC, and Cu0/AC catalysts (AC: activated carbon) were prepared by heat treatment of Cu2(NO3)(OH)3/AC in an inert atmosphere, and their catalytic properties for the direct vapor-phase oxidative carbonylation of methanol to dimethyl carbonate (DMC) were investigated. When the Cu2(NO3)(OH)3/AC was heated at 200 °C, the main copper species on AC was CuO. With the heating temperature rising, the CuO content decreased and the Cu2O content increased on the AC support. The Cu species existed as Cu2O when the heating tempareture was 400 °C and as Cu0 when the heating tempareture was 450 °C. The catalytic activity also increased with the heating temperature rising. This indicated that the CuO, Cu2O, or Cu0 was active, and the catalytic activity increased in the order CuO < Cu2O < Cu0. Under the conditions of 140 °C, CO:MeOH:O2 = 4:10:1, and SV = 5 600 h?1, the Cu0/AC catalyst prepared at 450 °C had excellent catalytic activity, and the methanol conversion, space time yield, and selectivity for DMC reached 11.5%, 261.9 mg/(g•h), and 76.0%, respectively.

Key words: methanol, oxidative carbonylation, copper, active carbon, chlorine free catalyst, heat treatment, dimethyl carbonate