Mechanism of NiMoO4 formation during oxidative regeneration of resid HDS catalyst

Aggregation of the active metal components as NiMoO4 during oxidative regeneration of residue hydrodesulfurization catalyst was studied by conventional and micro X-ray diffraction (XRD). The formation of NiMoO4 was observed only on catalyst regenerated above 723 K by conventional XRD. Distribution of NiMoO4 formation through the section of a catalyst particle was investigated by micro-XRD. The center of the catalyst particle showed higher aggregation of NiMoO4 compared to the outside of the catalyst. These results indicate that NiMoO4 formation is mainly caused by temperature increase inside the catalyst due to the heat accumulation from coke burning. Since the distribution of NiMoO4 was not associated with that of vanadium, which was mainly present on the outside of the catalyst particle, vanadium did not chemically affect the active metal states.