Dimethyl carbonate synthesis from carbon dioxide and methanol over Ni-Cu/MoSiO(VSiO) catalysts

The surface structures, chemisorption properties and catalytic behaviors of Ni-Cu/MoSiO and Ni-Cu/VSiO catalysts have been investigated by using the techniques of XRD, TPR, IR, TPD and micro-reactor. Three types of active sites, metallic site M (Ni-Cu alloy), Lewis acid site M^a+ (Mo⁶⁺ or V⁵⁺) and Lewis base site M=O (Mo=O or V=O), have been found on the surface of the reduced catalysts. With the cooperation effects of these active sites, CO₂ can be chemisorbed on the metallic site M and Lewis acid site M^a+ to form a new type of CO₂ horizontal adsorption state, M - (CO) - O→M^a+, and CH₃OH can be dissociated on the Lewis base site M=O and Lewis acid site Mⁿ⁺ to form a dissociative adsorption state, Mⁿ⁺ - OCH₃ and HO - M. The selectivity of dimethyl carbonate synthesized from these adsorption species is over 85% and a surface reaction mechanism of this catalytic reaction is proposed based on the experimental results.