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为了考察水蒸汽对金属/载体催化剂的影响,把氧化铝担载的Ni,Co或Fe催化剂在700℃的水蒸汽中进行加热。透射电镜图象证明,对这些催化剂,膜状斑点都从微晶粒向外扩展,延长加热时间导致金属斑点的消失,这些斑点状的金属可能扩展成为相互连接的薄膜铺展在整个基质表面上。铺展的程度有以下的顺序:Co>Ni>Fe。随后在H_2中加热,小的金属晶粒得到再生,这可能使相连的薄膜重新断开。桥结两个或若干个金属颗粒的块状膜的收缩引起颗粒的聚结。这个在H_2中的加热过程。只有当加热时间很短时才有助于金属的再分散。如果在H_2中延长加热时间则将导致小的颗粒消失。
In order to investigate the effect of steam on the metal / support catalyst, the alumina supported Ni, Co or Fe catalyst was heated in water vapor at 700 ° C. Transmission Electron Microscopy (TEM) images demonstrate that for these catalysts, the film-like spots all extend outward from the micrograins, prolonging the heating time resulting in the disappearance of metal spots that may expand into interconnected films spreading over the entire substrate surface. The extent of spreading is in the following order: Co> Ni> Fe. Subsequent heating in H 2, small metal grains are regenerated, which may reconnect the connected film. The shrinkage of the massive film bridging two or more metal particles causes coalescence of the particles. This heating process in H2. Only when the heating time is very short to help redisperse metal. Prolonging the heating time in H 2 will result in the disappearance of small particles.