New perspectives about the role of cobalt in hydrodesulfurization catalysis

The disordered state of Co(Ni) promoted MoS ₂-based catalysts has hindered the understanding of the structure/function relationships in these solids. Synchrotron X-ray scattering reveals features otherwise undetectable using classical sources of X-rays that leads to a complete determination of the dispersion of well-dispersed supported catalysts. In combination with HREM, this technique has led to new important results about CoMo catalysts: Co promotion strongly favors the formation of multilayered slabs; hydrotreating conditions induce a destacking process that results from a combination of carbonaceous deposits and high pressure during reaction (commercial CoMo/Al ₂O ₃ catalysts tend to destack with time of use); and using a synchrotron source revealed the presence of Co ₉S ₈ as a secondary phase which tends to be reduced into Co metal under severe conditions. This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA 8/22-26/2004).