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Abstract
Four types of metal deposition profiles have been observed in spent catalysts after the hydro-demetallation of residual oils. They are: (1) Uniform deposition profile, characterized by an absence of diffusion limitations. (2) Edge maximum profile, characterized by a U-shaped distribution. (3) Shell maximum profile, characterized by a M-shaped distribution where the maximum is at a shell that is neither at the edge nor at the center. (4) Center maximum profile. These four patterns can be explained by a consecutive mechanism involving an intermediate B, which is not originally in the residual oil: A – B → C. The shell maximum and the center maximum can only occur near the reactor inlet, before the build-up of intermediate B in the oil.