Unraveling the Redox Behavior of a CoMoS Hydrodesulfurization Catalyst: A Scanning Transmission X-ray Microscopy Study in the Tender X-ray Range

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• 作者：Mustafa Al Samarai ; Florian Meirer ; Chithra Karunakaran ; Jian Wang ; Eelco T. C. Vogt ; Henny W. Zandbergen ; Thomas Weber ; Bert M. Weckhuysen ; Frank M. F. de Groot
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：February 5, 2015
• 年：2015
• 卷：119
• 期：5
• 页码：2530-2536
• 全文大小：440K
• ISSN：1932-7455

文摘

We visualize the elemental zoning in an alumina-supported cobalt molybdenum sulfide (CoMoS) catalyst with scanning transmission X-ray microscopy (STXM). We use the Canadian Light Source beamline 10-ID鈥檚 (SM) unique combination of soft X-ray and tender X-ray STXM to determine the spatial variation of Co, Al, Mo, and S species. The results clearly show the correlation between cobalt and molybdenum and the anticorrelation between cobalt and alumina, confirming that Co is closely associated with the MoS₂ phase. The tender X-ray STXM images show that the fresh catalyst particle contains a 50 nm ring of molybdenum oxide encapsulating the supported MoS₂ phase. After the reduction at 200 掳C with H₂, this oxide rim disappears and a uniform MoS₂ distribution is found. Upon oxidation at 400 掳C, the sulfur disappears from the catalyst sample and molybdenum is oxidized from a Mo^IV sulfide to a mainly tetrahedral Mo^VI oxide, while cobalt keeps its divalent nature and changes from a Co^II sulfide to a Co^II oxide.