Evidence for kinetic and oxidative stabilization of Rh on Mo-promoted RhAl2O3
Evidence for kinetic and oxidative stabilization of Rh on Mo-promoted RhAl2O3
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Mo 促进的 RhAl2O3 上 Rh 的动力学和氧化稳定性的证据
DOI：
10.1016/1381-1169(95)00177-8
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发表时间：
1995
影响因子：
--
通讯作者：
H. C. Foley
中科院分区：
文献类型：
--
作者：
Eric E. Lowenthal;L. Allard;M. Te;H. C. Foley
在我们的实验室中进行的二氧化硅和氧化铝负载的Rh催化剂上的一氧化碳加氢研究以及文献中报道的那些研究表明，向催化剂表面添加早过渡金属氧化物对活性Rh中心产生促进影响。这种促进导致含氧化合物选择性增强。早期过渡金属氧化物的促进作用的解释分为三类：（i）小Rh聚集体的动力学稳定，（ii）过渡金属氧化物的润湿和铺展，导致Rh微晶表面的装饰，以及（iii）Rh聚集体的氧化稳定，改变Rh在反应过程中与亚羰基的相互作用。Rh_xMo_γ-Al_2 O_3体系的表征为Rh聚集体的动力学稳定化和氧化稳定化提供了支持证据，并表明这些过程有助于提高这些材料的选择性。氢和一氧化碳的化学吸附结果提供了证据，高度分散和氧化稳定的Rh聚集体。即使在延长的运行测试（> 10小时）后，金属聚集是不可避免的，高分辨率透射电子显微镜，相关的能量色散光谱，并使用快速傅立叶变换后处理，以产生光学衍射图突出的差异，在金属聚集体形态。
Carbon monoxide hydrogenation studies on silica- and alumina-supported Rh catalysts conducted in our laboratories as well as those reported in the literature suggest that the addition of early transition-metal oxides to the catalyst surface exerts a promotional influence on active Rh centers. This promotion leads to enhanced oxygenate selectivity. Explanations of the promotional influence of the early transition-metal oxides fall into three categories: (i) kinetic stabilization of small Rh aggregates, (ii) wetting and spreading of the transition-metal oxide, leading to decoration of the surface of Rh crystallites, and (iii) oxidative stabilization of Rh aggregates, altering Rh interactions with sub-carbonyls during reaction. Characterization of the RhMo γ- Al2O3system provides supporting evidence for both kinetic stabilization and oxidative stabilization of Rh aggregates and suggests that these processes contribute to the enhanced oxygenate selectivity of these materials. Hydrogen and carbon monoxide chemisorption results provide evidence for highly dispersed and oxidatively stabilized Rh aggregates. Even after extended on-stream testing (> 10 h), where metal aggregation is unavoidable, high-resolution transmission electron microscopy, associated energy dispersive spectroscopy, and the use of fast-Fourier transform post-processing to produce optical diffractograms highlight differences in the metal-aggregate morphology.