On the Role of Promoter Atoms in Unsupported Hydrodesulfurization Catalysts: Influence of Preparation Methods

This is the authors' abstract. We don't add key points for this paper.

Unsupported Co‐Mo catalysts were prepared by two different methods:by the co‐maceration (CM) method and by a new homogeneous sulfide precipitation (HSP) method. Structural examinations by means of XRD and Mössbauer Emission Spectroscopy (HES) show that the CM catalysts contain several phases with Co9S8 being the dominant cobalt containing phase. On the other hand, the HSP catalysts are shown to contain only one CO phase within an extended range of Co/Mo atomic ratios and this phase is the Co‐Mo‐S phase. Like in the case of supported catalysts, the Co‐Mo‐S phase is shown to be the phase responsible for the activity, whereas Co9S8 is shown to have little or no influence on the activity. The differences in activity observed between the HSP and CM catalysts as well as other unsupported catalysts studied in the literature all seem to be related to differences in the preparation procedures resulting in different promotional efficiencies for the formation of Co‐Mo‐S.