Abstract: The effect of catalyst pore diameter on the metal deposition distribution and hydrodemetallization conversion of residue oil were investigated over well-defined and uniform pore-structure catalysts. The hydrodemetallization of Saudi Arabia vacuum residue was conducted in a batch stirred autoclave at 400 ℃,10 MPa H2 pressure. Samples of the used catalysts were characterized by SEM and EDX to elucidate the deposition distribution of Ni and V in catalyst pellets. The contents of Ni and V in the hydrodemetallized oil were measured by AES-ICP. The results show that the Ni and V metal deposition profiles are uniform on the two catalysts with pore size larger than 47 nm, indicating that the reaction is controlled by chemical reaction rather than by internal diffusion of reactants. When the catalyst pore size is smaller than 17 nm, the maximum amount of metals deposition appears at the entrance of the catalyst pellets, and decreases along the axial toward the center of the catalyst pellets, indicating the HDM reaction is diffusion control process. The deposition profiles of Ni and V are different from each other, showing that the ratios of reaction rate to the diffusion rate are different for the two metal compounds.

Key words: model catalyst, hydrodemetallization, pore diameter, metal deposition, diffusion