Unblocking of NiMo Active Sites for Hydrodesulfurization Catalysts: A Study Focused on Inactive Ni_xS_y Segregation

Abstract

The formation of Ni x S y /Co x S y phases on the HDS catalyst surface during catalyst preparation poses the following challenges in the HDS reaction: (1) inactive in the reaction, (2) hinder the role of promoters, (3) block the actives sites (NiMoS/CoMoS) at the perimeter, and (4) increase the inert mass on 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. In this regard, this work investigates the effect of metal-support interactions and catalyst compositions on Ni x S y phase separation and removal of Ni x S y phases from the catalyst surface using acid-leaching method. The HDS activity for NiMo supported on amorphous alumina (NiMo/A-Al 2 O 3 ) catalysts significantly increased after the acid-leaching treatment by unblocking the active NiMoS sites and increasing the Ni-MoS 2 interaction through alumina support leaching. Overall, the HDS activity for leached NiMo/A-Al 2 O 3 catalysts is 25−30% higher than that for conventional NiMo/γ-Al 2 O 3 catalysts.