MoO3在介孔分子筛MCM-41上分散和存在状态的研究

在773K加热MoO3和MCM－41的机械混合物，可以实现MoO3分散在介孔分子筛MCM－41表面，用透射电镜和选区电子衍射，配合XRD和液氮温度下氮吸附－脱附曲线和BJH孔径分布，研究了活性组分MoO3在有序介 材料MCM－41上的存在状态，以及MoO3分散到MCM－41表面后MCM－41的结构变化情况。结果表明：当MoO3的含量小于单层分散阈值，加热后MoO3的XRD衍射峰彻底消失，用HRTEM观察不到分散在MCM－41表面或孔道中的MoO3颗粒，而EDS能谱证明在MCM－41的孔道中有呈分散态的MoO3存在。MoO3的含量大于单层分散阈值，通过加热不能使MoO3完全分散在MCM－41表面，而且XRD、HRTEM、氮吸附－脱附等温线和孔径分布都表明由于MoO3的分散量较大，载体MCM－41的有序介孔结构遭到破坏。

Dispersion of MoO3 Supported on Mesoporous Sieves MCM-41

MoO3 can disperse onto the surface of mesoporous sieves MCM-41 by calcining the physical mixtures of MoO3 and MCM-41 at 773K. The state of active component MoO3 on ordered mesoporous MCM-41 was studied by TEM and SAED along with XRD, N2 sorption isotherms and BJH pore size distribution. The change for MCM-41 structure was also studied after MoO3 dispersed onto MCM-41. The results show that the XRD peaks of bulk MoO3 disappear completely when the loading of MoO3 is less than the monolayer dispersion capacity. The dispersed MoO3 can not be observed by HRTEM, while EDS spectrum evidences that there is dispersed MoO3 in the mesopores of MCM-41. It is not possible that MoO3 disperses onto MCM-41 absolutely by calcining when the content of MoO3 is more than the critical dispersion capacity. XRD, HRTEM, N2 sorption isotherms and BJH pore size distribution results all reveal that the ordered structure of MCM-41 is destroyed for the larger amount of dispersed MoO3.