Surface structure and sulfidation behavior of Co-Mo and Co-W sulfide catalysts for the hydrodesulfurization of dibenzothiophene

• The formation of Co-W-S and Co-Mo-S active sites was investigated by in situ XAFS.
• The Co-W-S coverage was found to be smaller than the Co-Mo-S coverage.
• The degree of active site blocking of WS2 by Co9S8 was higher than that of MoS2.

The catalytic property and local structure of Co-MoS2 and Co-WS2 catalysts were investigated by means of the Co-CVD technique using Co(CO)3NO and XAFS. Comparing the catalytic activity for the HDS of DBT between Co-MoS2 and Co-WS2 catalysts before and after the CVD treatment, it was shown that the Co coverage of the edge sites of WS2 particles is lower than that of MoS2 particles, leading to a smaller amount of the Co-W-S structure in the catalyst. Furthermore, edge sites of WS2 particles are more extensively blocked by excess Co sulfide particles than those of MoS2 particles at a high Co loading (>5 wt%). In situ, W L3-edge, Mo K-edge and Co K-edge XAFS analyses during catalyst sulfidation revealed that sulfidation temperature of W atoms is much higher than those of Mo and Co. The difficulty in the formation of Co-W-S on the Co-WS2 catalysts is related to this specific sulfidation behavior of W.

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