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采用表面改性法制备了负载型Sn2 (OMe) 4 /SiO2 双核桥联配合物催化剂 ,用IR ,TPD和微反技术对催化剂的表面结构、化学吸附性质和催化活性进行了研究 .结果表明 ,双核桥联Sn2 (OMe) 4 /SiO2 配合物中存在Sn O Si双齿配位形式 ,甲氧基以桥基形式联结两个Sn4+ 离子 ;CO2 在催化剂表面以桥式吸附态和甲氧碳酸酯基吸附态存在 ,而CH3 OH只以分子吸附态存在 .在反应温度 4 13K ,压力 0 5MPa ,反应空速 15 0 0h-1以及CH3 OH与CO2 的摩尔比为 2～ 2 5的反应条件下 ,CO2 和CH3 OH在Sn2 (OMe) 4 /SiO2 催化剂上生成碳酸二甲酯的选择性达到近 10 0 % .根据实验结果 ,提出了CO2 与CH3 OH在Sn2 (OMe) 4 /SiO2 催化剂表面上的反应机理 ,反应物分子共吸附于催化剂表面同一活性位上及CO2 的甲氧碳酸酯基吸附态的形成是反应顺利进行的关键因素 .
The surface-modified SnO2 (OMe) 4 / SiO2 binuclear bridged complex catalysts were prepared by surface modification method, and the surface structures, chemisorption properties and catalytic activities of the catalysts were investigated by IR, TPD and micro- SnO Si bidentate coordination forms exist in the binuclear Sn2 (OMe) 4 / SiO2 complex, while the methoxy groups bridge two Sn4 + ions in the form of bridge. CO2 adsorbed on the surface of the catalyst in the form of bridged carbon dioxide While CH3OH exists only in molecular adsorption state. Under the reaction conditions of reaction temperature 4 13K, pressure 0 5MPa, reaction space velocity 15 0 0h-1 and molar ratio of CH3 OH to CO2 of 2 ~ 25 , The selectivity of CO2 and CH3OH to dimethyl carbonate on Sn2 (OMe) 4 / SiO2 catalyst reaches nearly 100% .According to the experimental results, we propose a new method to synthesize dimethyl carbonate on Sn2 (OMe) 4 / The reaction mechanism, the total adsorption of reactant molecules on the same active site on the surface of the catalyst and the formation of CO2 adsorption state of methoxy carbonates are the key factors for the smooth progress of the reaction.