Promoted partial oxidation activity of supported Ag catalysts in the gas-phase catalytic oxidation of benzyl alcohol
Promoted partial oxidation activity of supported Ag catalysts in the gas-phase catalytic oxidation of benzyl alcohol
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DOI：
10.1016/j.jcat.2005.06.032
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发表时间：
2005-09
影响因子：
7.3
通讯作者：
Ryohei Yamamoto;Yo-suke Sawayama;H. Shibahara;Y. Ichihashi;S. Nishiyama;S. Tsuruya
中科院分区：
文献类型：
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作者：
Ryohei Yamamoto;Yo-suke Sawayama;H. Shibahara;Y. Ichihashi;S. Nishiyama;S. Tsuruya
用负载在SiO_2或CaO载体和K/Ag/SiO_2载体上的银催化剂对苯甲醇进行了气相催化氧化反应，考察了活性银物种的表面状态、碱载体和添加碱金属的影响。苯甲醛是主要的氧化产物。考察了Ag/SiO2催化剂的焙烧温度和反应温度对氧化活性的影响。在553~593K温度范围内，苯甲醛的产率显著提高，焙烧温度从773 K提高到1173K时，苯甲醛的部分氧化活性也显著提高。在较低的反应温度下，Ag物种的CaO载体和添加到Ag/SiO_2催化剂中的K都促进了部分氧化。X射线衍射和扩展X射线吸收精细结构表明，较高的焙烧温度、碱性载体和碱金属的加入使负载的银更容易还原为金属银。根据负载型银催化剂的吸氧量和漫反射光谱，推测金属银表面被氧化的银物种是苯甲醇部分氧化的活性银组分。
The gas-phase catalytic oxidation of benzyl alcohol was carried out using Ag catalysts impregnated on a SiO2or CaO support, as well as a potassium-added counterpart (K/Ag/SiO2), to clarify the surface state of the Ag species active in the oxidation reaction, the effect of the basic support and the added alkali metal. Benzaldehyde was obtained as the main oxidation product. The effects of the calcination temperature of the Ag/SiO2catalyst and the reaction temperature on oxidation activity were investigated. The benzaldehyde yield markedly increased between 553 and 593 K. Increasing the calcination temperature from 773 to 1173 K also caused a significant increase in partial oxidation activity. Both a CaO support for the Ag species and potassium added to the Ag/SiO2catalyst promoted partial oxidation at a comparatively low reaction temperature. X-ray diffraction and extended X-ray absorption fine structure demonstrated that a high calcination temperature, a basic support, and addition of an alkali metal led to a more ready reduction of the supported Ag to metallic Ag. Oxidized surface Ag species on the metallic Ag were inferred to be the active Ag components for the partial oxidation of benzyl alcohol based on the amount of O2uptake and the diffuse reflectance spectra of the supported Ag catalysts.