Carbon deposition in Pd/CeO2 catalyst: TEM study
Carbon deposition in Pd/CeO2 catalyst: TEM study
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Pd/CeO2 催化剂中的碳沉积：TEM 研究
DOI：
10.1016/s0920-5861(98)00506-9
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发表时间：
1999
期刊：
影响因子：
5.3
通讯作者：
L. Kępiński
中科院分区：
文献类型：
--
作者：
L. Kępiński
用透射电子显微镜和选区电子衍射仪研究了Pd/CeO2催化剂、Pd黑和Pd3Ce合金在873K加热过程中积炭的形态和分布。在Pd/CeO2催化剂中形成了丝状碳，其微观结构强烈依赖于催化剂在氢气中还原的温度。在673和773K还原的样品呈现“晶须状”的生长方式(金属颗粒位于细丝的顶端)，而在973和1100K还原的样品产生“挤压状”的细丝(Pd颗粒位于底部，附着在CeO_2微晶上)。Pd/CeO2催化剂在1200K的还原完全阻止了碳丝的形成。Pd黑中存在大量的晶须和贝壳状碳沉积，而Pd3Ce合金中未观察到碳沉积。Pd-CeO_2相互作用(Pd颗粒在CeO_2上的外延取向、部分还原的CeO_3修饰Pd表面以及Pd-Ce合金的形成)随还原温度的升高而改变。
Morphology and distribution of carbon deposit accumulated in Pd/CeO2catalyst, Pd black and Pd3Ce alloy during heating in ethylene at 873K was studied by transmission electron microscopy (TEM) and selected area electron diffraction (SAED). In Pd/CeO2catalyst filamentous carbon was formed, with microstructure depending strongly on temperature of the catalyst reduction in hydrogen. Samples reduced at 673 and 773K produced filaments exhibiting “whisker-like” mode of growth (metal particles were located at the tip of the filaments), while those reduced at 973 and 1100K produced “extrusion-like” filaments (Pd particles were located at the bottom, attached to ceria crystallites). Reduction of the Pd/CeO2catalyst at 1200K hindered completely the formation of carbon filaments. Extensive carbon deposit in the form of whiskers and shells occurred in Pd black, while no carbon deposition was observed in Pd3Ce alloy. The change in the filament growth mode with increasing temperature of reduction has been explained by increasing strength of the Pd–ceria interaction (epitaxial orientation of Pd particles on CeO2, decoration of Pd surface with partly reduced ceria species and formation of Pd–Ce alloy).