Abstract: Residue hydrotreating spent catalysts after pretreatment with toluene were characterized by C and S content analysis, XRF, XRD, SEM and TG techniques. The results showed that the metallic impurity was mainly captured by layered catalysts system consisted of the guard catalyst, guard-demetallization catalysts, demetallization catalysts and demetallization-desulfurization catalysts in sequence. The captured metal ultimately deposited on the spent catalyst as NiV₂S₄, while coke was mostly observed on desulfurization catalysts and carbon removal catalyst. Along the flow direction, the coke deposited gradually transferred from soft coke to hard coke and the amount increased. The amount of metal deposition and decomposition temperature increased first and then decreased, and the amount of metal deposition was the maximum in demetallization catalysts, and the molecular structure of sediment was the most complex. The guard-demetallization catalyst and demetallization catalyst system was hardened badly and along the flow direction, V content firstly increased and then decreased, Fe content decreased, while Ni and Ca content was evenly distributed where Fe was mainly deposited on the outer surface, the distribution of Ni element was relatively uniform, V existed more at the edge of the catalyst with lower in center. The distributions of V along the cross section of demetallization catalyst and demetallization-desulfurization catalyst were V-shaped, while on the desulfurization catalyst and carbon residue removal catalyst were U-shaped and distributed on the surface of catalyst particles. Suggestions for catalyst design were proposed.

Key words: residue hydrotreating, catalyst, deactivation, coke deposition, metal deposition