Unblocking of NiMo Active Sites for Hydrodesulfurization Catalysts: A Study Focused on Inactive Ni x S y Segregation

The formation of Ni x S y /Co x S y phases on the HDS catalyst surface during catalystpreparation posesthe following challenges in the HDS reaction: (1) inactive in thereaction, (2) hinder the role of promoters, (3) block the activessites (NiMoS/CoMoS) at the perimeter, and (4) increase the inert masson the catalyst surface. Since the formation of Ni x S y /Co x S y phases is thermodynamically favorable,it is difficult to control this during the catalyst synthesis. Inthis regard, this work investigates the effect of metal-support interactionsand catalyst compositions on Ni x S y phase separation and removal of Ni x S y phases from the catalystsurface using acid-leaching method. The HDS activity for NiMo supportedon amorphous alumina (NiMo/A-Al2O3) catalystssignificantly increased after the acid-leaching treatment by unblockingthe active NiMoS sites and increasing the Ni-MoS2 interactionthrough alumina support leaching. Overall, the HDS activity for leachedNiMo/A-Al2O3 catalysts is 25-30% higherthan that for conventional NiMo/gamma-Al2O3 catalysts.