Solid State Synthesis and Characterization of Model Hydrodesulfurization Catalysts

Solid-state reactions of elemental sulfur with metallic cobalt and molybdenum powders were used to synthesize model catalysts for hydrodesulfurization (HDS). The resulting materials had a general stoichiometry of CozlMo,-,S2 with x between 0.025 and 0.3. The solid phases formed during synthesis and after exposure to typical HDS reaction conditions were identified by X-ray diffraction and selected area electron diffraction. The catalytic activity for hydrodesulfurization of thiophene was tested in a flow reactor. High activity for hydrodesulfurization coincided with the presence of a nonstoichiometric bulk phase. It was found that introducing small quantities of a promoter atom led to similar activity trends, XRD patterns, and electron microscopy results, all of which were attributed to a nonstoichiometric bulk phase. The structure of this phase is not yet fully determined but is consistent with a defect structure of MO& having anionic vacancies. o 1989