Study on Cu-Ni/ZrO₂-SiO₂ catalyst for direct synthesis of DMC from CO₂ and CH₃OH

The surface complex support ZrO₂-SiO₂ (ZrSiO) was prepared by surface reaction modification, and Cu-Ni/ZrSiO bimetallic catalyst was prepared by isovolumic impregnation. Absorption and reaction of CO₂ with methanol on the catalyst were characterized by IR spectroscopy, TPD, temperature-programmed surface reaction, and microreactor techniques. The results showed that there exist three kinds of active sites on the catalyst: metal site M, Lewis acid site Zrⁿ⁺, and Lewis basic site Zr-O^-; CO₂ horizontal adsorption state, formed from its shearing state on M with the cooperation of adjacent Zrⁿ⁺, can be dissociated into M-CO and Zr-O^- at ~ 142°C and methanol dissociated into Zr-OCH₃ and Zr-OH with the cooperation of Zrⁿ⁺ and adjacent Zr-O^-; the main reaction products on the catalyst are dimethyl carbonate (DMC) with a selectivity of > 85%, and less amounts of CH₂O, CO, and H₂O.