高效WO3掺杂MCF催化剂的合成及其在环戊烯选择氧化制戊二醛反应中的应用

以钨酸钠和正硅酸乙酯为前驱体直接合成高含量WO₃掺杂介孔氧化硅泡沫(MCF)催化剂. 在773 K焙烧后显示出更高的热稳定性. 小角X射线散射, N₂-物理吸附和透射电子显微镜结果表明钨物种嵌入后, 材料仍保持MCF特征的三维织构介孔特征. 紫外拉曼和紫外可见漫反射光谱结果表明钨物种主要以孤立的或者低聚态的氧化钨形式存在, 所以在氧化钨质量分数(w)低于20%时氧化钨物种能够高度分散在载体上. 在环戊烯选择氧化制戊二醛反应中, 反应16 h 后环戊烯的转化率达到100%, 戊二醛的产率达到83.5%. 催化剂重复利用实验表明催化剂的稳定性较好, 没有钨物种的脱落. 这种优异的催化性能归结于合适的氧化钨含量和高分散的钨物种.

Synthesis of Highly Efficient WO3-Doped MCF Catalyst and Its Application in the Selective Oxidation of Cyclopentene to Glutaraldehyde

We synthesized WO3 doped mesocellular silica foam (WO3-doped MCF) catalysts with a high tungsten oxide content of 20% (w, mass fraction) directly using sodium tungstate and tetraethylorthosilicate as precursors. The catalysts showed high thermal stability after calcination at 773 K. Small-angle X-ray scattering, N2 adsorption, and transmission electron microscopy results indicated that the characteristic three dimensional mesocellular structural features of the MCFs were retained after the incorporation of tungsten oxide species. Ultraviolet-Raman and ultraviolet-visible diffuse reflectance spectroscopy data showed that isolated or lowly condensed oligomeric tungsten oxide species were obtained for the WO3-doped MCF catalysts. These oxide species were stable and highly dispersed in the silica-based MCF matrix with a tungsten oxide content lower than 20% (w). We found that the nature of the tungsten species largely depended on its content and the direct synthesis method was beneficial in obtaining highly dispersed tungsten oxide species. In the selective oxidation of cyclopentene (CPE) to glutaraldehyde (GA), the 20% (w) WO3-doped MCF catalyst had a CPE conversion of 100% and a GA yield of 83.5% after reacting for 16 h. Furthermore, very stable catalytic activity after many recycling tests was apparent for the WO3-doped MCF catalyst indicating that almost no tungsten species was leached into the reaction solution. A proper amount of tungsten oxide and its high dispersion accounted for the high activity.