通过动态法以哌啶(PI)作为模板剂,硼酸作为结构承载助剂,硅溶胶作为硅源,钨酸钠作为钨源,水热晶化合成了W—MCM-22介孔分子筛。采用X射线粉末衍射、紫外可见分光光谱等分析手段对合成的材料进行了表征,考察了不同W含量的分子筛在烯丙醇环氧化反应中的催化氧化性能,并与不含金属的MCM-22催化剂进行比较。结果表明,当n(Si)/n(W)〉40时,所合成的分子筛具有典型的MCM-22分子筛的拓扑结构,W原子进入了分子筛骨架内,不存在钨的氧化物。在烯丙醇催化环氧化制缩水甘油反应中,当n(Si)/n(W)-40时,水热晶化法制备的W—MCM-22分子筛的催化活性明显高于不含金属的MCM-22分子筛。
Mesoporous W-MCM-22 molecular sieves were prepared for the first time by directly hydrothermal synthesis using silica gel as the source of silicon, sodium tungstate as the tungsten source, piperidine as a structuredirecting agent(SDA) and boric acid as a structure-supporting agent under dynamic state. The catalyst was characterized and analyzed by powder X-ray diffraction and UV-visible spectroscopy. The influence of tungsten content on catalytic performance for epoxidation of allyl alcohol was investigated. The catalytic performances of W-MCM-22 with different ratio of n(Si)/n(W) were compared with the zeolite of MCM-22 without adding sodium tungstate in synthesis. The results showed that the mesostructure of MCM-22 was maintained very well in W-MCM-22 as-synthesized when the ratio of n(Si)/n(W) was above 40 in the gel. The tungsten atoms entered the framework dispersively, and there was no any kind of tungsten oxide in the framework. The W-MCM-22 with n(Si)/n(W) of 40 in the gel showed better catalytic performance obviously than MCM-22 for epoxidation of allyl alcohol to glycidol, with hydrogen peroxide as oxidant in aqueous.