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

点击翻译按钮获取中文摘要

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.