The Influence of Metal Deposits on Residue Hydrodemetallization Catalysts in the Absence and Presence of Coke

Spent hydrodemetallization (HDM) catalysts were collected from pilot-scale reactors with different time-on stream, and they were treated with an extraction or regeneration method for further investigation. The fresh, spent, and regenerated samples were characterized systematically. Their catalytic performances were assessed using model molecules and Kuwait atmospheric residue as the reactants. Compared with conventional NiMo/Al2O3 catalysts, deposited metal sulfides had a notable increase in their HDM activity but an obvious decrease in their naphathelene hydrogenation activity. With short contact time, metal deposits accelerated residue HDM activity, and they were also involved in the loss of hydrodesulfurization (HDS) activity. At the initial stage of operation, HDM activity was reduced significantly due to the formation of coke. However, coke and metal deposits together contributed to the loss of HDS activity and the rapid fall of long period on-stream HDM activity.