Effect of sulfidation atmosphere on the hydrodesulfurization activity of SiO2-supported Co–Mo sulfide catalysts: Local structure and intrinsic activity of the active sites

The effects of the sulfidation atmosphere on the local structure and intrinsic activity of the active sites, Co–Mo–S, are studied with SiO2-supported Co–Mo sulfide catalysts prepared by a chemical vapor deposition method using Co(CO)3NO. The Co–Mo sulfide catalysts were sulfided in a stream of 10% H2S/H2 or 10% H2S/He or their combinations. The intrinsic activity of Co–Mo/SiO2 presulfided in H2S/He is 1.6 times as high as that of Co–Mo–S Type II presulfided in H2S/H2 for the hydrodesulfurization (HDS) of thiophene, demonstrating that the location and/or local structure of Co–Mo–S are varied by the sulfidation atmosphere as well as by the MoS2-support interaction. The catalysts were characterized by X-ray absorption fine structure and transmission electron microscope. It is suggested that the intrinsic activities of Co–Mo–S on the S-edge and Mo-edge of MoS2 particles are distinctly different for HDS. Extended X-ray absorption fine structure analysis shows a good correlation between the coordination number of Co–S and the intrinsic activity of “active Co–Mo–S”.