(89c) Effect of Promoters on Structural and Chemical Properties of Hydrotreating Catalysts

In recent years, our knowledge of the atomic structure of the active MoS₂ phase in hydrotreating catalysts has increased. However, commercial catalysts are typically promoted with Co or Ni, whereby the activity is increased by more than an order of magnitude. It is also known that the selectivity and the relative importance of the hydrogenating and direct desulfurization route are altered by the introduction of these promoters. Additionally, Co and Ni promoted catalysts react differently to the reaction conditions and feed composition. Especially the basic nitrogen compounds are known to inhibit the hydrogenation pathway that involves the metallic-like brim sites. By combining experimental results from microscopy (STM and HAADF-STEM) and theoretical DFT calculations, we have learned that the Ni and Co significantly influence the structure of the active sulfide phase. From this new insight, the results from both model and real feed tests can be rationalized.