Time-Resolved XAS Investigation of the Local Environment and Evolution of Oxidation States of a Fischer–Tropsch Ru–Cs/C Catalyst
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- 作者：José L. Eslava ; Ana Iglesias-Juez ; Giovanni Agostini ; Marcos Fernández-Garcı́a ; Antonio Guerrero-Ruiz ; Inmaculada Rodrı́guez-Ramos
- 刊名：ACS Catalysis
- 出版年：2016
- 出版时间：March 4, 2016
- 年：2016
- 卷：6
- 期：3
- 页码：1437-1445
- 全文大小：477K
- ISSN：2155-5435
文摘
Here we present a time-resolved in situ X-ray absorption spectroscopy investigation of the local chemical environment and the electronic structure of the active metal (Ru) and the promoter (Cs) present in catalysts supported over high-surface-area graphite. These catalysts were submitted to a reduction treatment under hydrogen gas and then to alternate atmospheres of Fischer–Tropsch reactants, CO/He, and H2/He atmospheres, respectively. This study reveals that Ru reduction is a complex process taking place through a two-step mechanism via an intermediate oxidation state and occurs in parallel to the Cs partial reduction. It also demonstrates a close association between Cs and Ru atoms as first neighbors. The evidence that the Ru–Cs particle morphology reverses (from flat 2D to a 3D shape with low coordination numbers) when the H2 atmosphere is changed with CO proves the strong interaction of CO with the surface of the Ru–Cs nanoparticles, a point confirmed by microcalorimetry of CO adsorption. To our knowledge, this is the first time that this reversible particle reconstruction upon syngas reactant switching has been demonstrated.