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-IDs (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 degrees C with H-2, this oxide rim disappears and a uniform MoS2 distribution is found. Upon oxidation at 400 degrees C, the sulfur disappears from the catalyst sample and molybdenum is oxidized from a MoIV sulfide to a mainly tetrahedral MoVI oxide, while cobalt keeps its divalent nature and changes from a CoII sulfide to a CoII oxide.
|Number of pages||7|
|Journal||The Journal of Physical Chemistry Letters|
|Publication status||Published - 2015|
Al Samarai, M., Meirer, F., Karunakaran, C., Wang, J., Vogt, ETC., Zandbergen, HW., Weber, T., Weckhuysen, BM., & de Groot, FMF. (2015). Unraveling the Redox Behavior of a CoMoS Hydrodesulfurization Catalyst: A Scanning Transmission X-ray Microscopy Study in the Tender X-ray Range. The Journal of Physical Chemistry Letters, 119(5), 2530-2536.