Catalytic hydrodesulfurization over the Mo(100) single crystal surface II. The role of adsorbed sulfur and mechanism of the desulfurization step

摘要: The study of thiophene hydrodesulfurization (HDS) over initially clean Mo(100) surfaces has been extended to include sulfided surfaces. Low sulfur coverages (0 ≤ θs$0.67) inhibit HDS activity. Increasing the coverage in range 0.67 θs 1.0 produces a surface with an activity about half that surface. Excessive exposure sulfur-containing environment results formation MoS2 layer which is, at least part, responsible for complete catalytic deactivation. Radiotracer (35S) labeling techniques have used measure rates hydrogenation adsorbed on In ambient atmospheres both hydrogen (1 atm) and reaction mixture (P(H2) = 1 atm, P(Th) 2.5 Torr) rate is two orders magnitude less than rate. This fact suggest desulfurization step does not proceed via tightly bound MoS species.