Tracking Rh Atoms in Zeolite HY: First Steps of Metal Cluster Formation and Influence of Metal Nuclearity on Catalysis of Ethylene Hydrogenation and Ethylene Dimerization

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• 作者：Dong Yang ; Pinghong Xu ; Nigel D. Browning ; Bruce C. Gates
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2016
• 出版时间：July 7, 2016
• 年：2016
• 卷：7
• 期：13
• 页码：2537-2543
• 全文大小：537K
• 年卷期：0
• ISSN：1948-7185

文摘

The initial steps of rhodium cluster formation from zeolite-supported mononuclear Rh(C₂H₄)₂ complexes in H₂ at 373 K and 1 bar were investigated by infrared and extended X-ray absorption fine structure spectroscopies and scanning transmission electron microscopy (STEM). The data show that ethylene ligands on the rhodium react with H₂ to give supported rhodium hydrides and trigger the formation of rhodium clusters. STEM provided the first images of the smallest rhodium clusters (Rh₂) and their further conversion into larger clusters. The samples were investigated in a plug-flow reactor as catalysts for the conversion of ethylene + H₂ in a molar ratio of 4:1 at 1 bar and 298 K, with the results showing how the changes in catalyst structure affect the activity and selectivity; the rhodium clusters are more active for hydrogenation of ethylene than the single-site complexes, which are more selective for dimerization of ethylene to give butenes.