Abstract: In the residue hydrotreating unit of a certain company, a high content of metals (nickel + vanadium) was contained in the feedstock, by which hydrodemetallization was made challenging.In the mid-to-late stage of operation, the metal (nickel and vanadium) content in the hydrotreated heavy oil exceeded 15 μg/g. An analysis of the industrial unit’s demetallization performance revealed that the hydrodemetallization rate was negatively correlated with the (asphaltene and resin) content in the feedstock. Further comparative analysis was conducted on the asphaltene molecular structures of the feedstock for the residue hydrotreating unit in above company (referred to as Residue A) and the feedstock for a reference residue hydrotreating unit (referred to as Residue B). The results show thatthe asphaltenes in Residue A are characterized by a higher naphthenic carbon content and a lower paraffinic carbon content, and a more significant distribution of high double bond equivalent values and high carbon numbers is found in its hydrocarbon components. Overall, the asphaltenes in Residue A exhibit a larger relative molecular weight and a higher degree of polycyclic condensation, making them more difficult to convert, which may affect the metal removal efficiency. Based on the research findings, a novel demetallization catalyst named as RDM-301was developed and a graded catalyst system trial was conducted using Residue A as the feedstock. Compared with the previous catalyst grading, the demetallization rate was improved by 5.3 percentage points and the vanadium removal rate was improved by 7.6 percentage points by the new catalyst grading.

Key words: residue hydrotreating, metal, nickel, vanadium, molecular structure, catalyst grading