X-ray photoelectron spectroscopy surface quantification of sulfided CoMoP catalysts relation between activity and promoted sites - Part I: Influence of the Co/Mo ratio

This work is dedicated to the characterization of CoMoP/Al2O3 hydrotreatment catalysts. In order to identify the neighboring of cobalt and molybdenum, X-ray photoelectron spectroscopy (XPS), transmission electron spectroscopy (TEM) and activity measurements were used. Indeed, a quantitative XPS characterization was developed to study the effect of the Co/Mo atomic ratio on CoMoP-type hydrodesulfurization catalysts. Identification and quantification of the various species present on the surface of the catalysts were performed. We showed that the catalyst exhibiting both the maximum activity in hydrogenation of toluene and the maximum amount of CoMoS active, determined through the XPS quantitative analysis, is the catalyst with a Co/Mo atomic ratio equal to 0.5. However, all the cobalt atoms are not completely engaged in the CoMoS mixed phase.