Cu-Ni/V₂O₅-SiO₂ Catalyst for the Direct Synthesis of Dimethyl Carbonate from Carbon Dioxide and Methanol

The surface complex support of V₂O₅-SiO₂(VSiO) was prepared by the method of surface reaction modification. VSiO supported Cu-Ni bimetallic catalysts were made using isovolumic impregnation. Adsorption and reaction of CO₂ and CH₃OH on catalyst were characterized by IR, TPD, TPSR and micro-reactor techniques. The results show that three active sites exist on Cu-Ni/VSiO catalyst: metal site(Cu-Ni alloy, denoted M), Lewis acid site(Vⁿ⁺)*and Lewis basic site(V = O); horizontally adsorped CO₂, formed by shearingly adsorbed CO₂ on M in cooperation with the adjacent Vⁿ⁺, can dissociate into M-CO and V = O at about 138 °C and methanol dissociated into V - OCH₃ and V - OH cooperated with Vⁿ⁺ and adjacent V = O; the mainly reaction products of the reaction of CO₂ and CH₃OH on Cu-Ni/VSiO catalyst are DMC (with selectivity over 85%), CH₂O, CO and H₂O.