Oxidative Regeneration of Resid Hydrodesulfurization Catalyst-Effect of Vanadium Accumulation on Properties and Activities of Regenerated Catalyst-

Resid hydrodesulfurization catalyst was regenerated after commercial operation and the effect of vanadium accumulation during resid hydrotreating reaction on the following catalyst regeneration was investigated. Vanadium accumulation accelerated the aggregation of active metals such as NiMoO4. Moreover, vanadium accumulation lead to the formation of Al2(SO4)3 on the catalyst during regeneration. Although sulfur-containing species such as MoS2 and vanadium sulfide were present all over the catalyst particle before regeneration, Al2(SO4)3 only formed around the exterior of the catalyst particle after regeneration. Since the distribution of Al2(SO4)3 corresponded well to the vanadium distribution, vanadium species probably catalytically oxidized SO2 into H2SO4, and then transformed the alumina carrier around the vanadium to sulfate. The effect of vanadium accumulation on the resid hydrotreatment activities of the resulting regenerated catalyst was also investigated. The hydrodesulfurization, hydrodenitrogenation and hydrodemicrocarbon residue activities over the regenerated catalyst decreased with increasing amount of vanadium accumulation. Since the XRD results indicated that the formation of NiMoO4 increased with vanadium accumulation, the deactivation of HDS activity probably resulted from the decrease in the number of active sites due to aggregation of nickel and molybdenum. On the other hand, hydrodemetallization and hydrodeasphaltene activities increased with increasing amount of vanadium accumulation. Vanadium sulfide accumulated on the catalyst may have formed new hydrodemetallation and hydrodeasphaltenization active sites.