ABSTRACT
This chapter discusses that the promotion of the hydrodesulfurization (HDS) activity is linked to the presence of the Co-Mo-S structures. It describes the detailed structural and physicochemical description of Co-Mo-S. The chapter focuses on the Co-Mo-S type structures that have also been observed to be present in other hydrodesulfurization catalysts than those based on Co and Mo. The great current interest in hydrodesulfurization (HDS) and other hydrotreating reactions is related to the need for efficient upgrading of crude oil fractions or coal-derived liquids. Subsequent to the identification of the different Co phases in Co-Mo catalysts, much of the work has been aimed at understanding the catalytic significance of the different phases. Co-Mo-S has also been observed in silica-[61] and carbon-supported Co-Mo catalysts. Specifically, it has been found that in spite of the fact that many different phases may be present, the promotion of the HDS activity is linked to the presence of a Co-Mo-S structure.
