Control of the structure of intrazeolite metal oxide clusters and their catalytic properties

金属氧化物催化剂在工业中占有重要地位。对于负载型氧化物催化剂，其活性和选择性强烈依赖于载体和负载量，通常认为金属氧化物物种的分散性和簇合物的结构改变了它们的催化性能。然而，人们还没有完全理解它们。为了合理、科学地设计高效催化剂，需要了解表面金属氧化物物种的结构与其催化性能之间的关系。在本研究中，我们试图揭示分子筛内金属氧化物簇合物的结构与催化剂性能之间的关系，分子筛内金属氧化物簇合物的结构被认为是通过限制在均相沸石骨架中来很好地定义的。我们还研究了分子筛内金属硫化物簇合物。利用金属羰基技术，在分子筛孔内成功构建了Mo氧化物、Fe氧化物、Co硫化物、Mo硫化物和GO-Mo二元硫化物簇合物。通过X射线吸收光谱和FEFF程序确定了簇合物的结构。随着乙醇的氧化，氧化活性随氧化钼团簇尺寸的增大而增大。结果表明，Fe6Ox团簇形成于沸石的方钠石笼内，对NOx还原反应表现出较高的活性。用金属硫化物簇合物在沸石笼中生成了具有硫代立方烷结构的Co1Mo_2S_6簇合物，表明Co-Mo二元硫化物簇合物是工业上最重要的加氢精制催化剂活性中心的良好模型。

Metal oxide catalysts are very important in industry. With supported oxide catalysts, it is well known that their activities and selectivities strongly depend on the support and the amount of loading, It is usually assumed that the dispersion of metal oxide species and, accordingly, the structure of the clusters modify their catalytic performances. However, they are not fully understood yet. It is required to understand the correlations between the structure of surface metal oxide species and their catalytic performances for rational and scientific design of highly efficient catalysts. In the present study, we tried to disclose the correlations between the catalyst performance and the structure of intrazeolite metal oxide clusters, the structure of which is considered to be well defined by confinement in a homogeneous skeleton of the host zeolite. We studied intrazeolite metal sulfide clusters as well. Mo oxide, Fe oxide, Co sulfide, Mo sulfide, and Go-Mo binary sulfide clusters were successfully constructed in zeolite pores, using metal carbonyl techniques. The structure of the clusters was determined by X-ray absorption spectra and FEFF codes. With the oxidation of ethanol, it was found that the activity increases with increasing size of the Mo oxide clusters. It was shown that Fe_6Ox clusters are formed in sodalite cage of the zeolite and that these clusters exhibit high activities for NOx abatement reactions. 'With metal sulfide clusters, it was revealed that Co1Mo_2S_6 clusters possessing a thiocubane structure were produced in the zeolite cages. It was shown that the Co-Mo binary sulfide clusters served a good model of the active sites of industrially paramount hydrotreating catalysts.