Abstract: In order to inhibit the poison of heavy metals to catalytic cracking catalysts and improve product distribution, a simple, efficient and environmentally friendly multifunctional additive for catalytic cracking was successfully developped with non-toxic components. The action mechanism of the multifunctional additive was studied by TPR, BET, XRD and other methods, and the performance of the additive was further investigated in the catalytic cracking unit with riser reactor. The results showed that the additive can inhibit Ni contamination because its effective components undergo lattice substitution with Ni²⁺, slowing down the formation of Ni⁰; and the effective components can interact with V₂O₅ to generate highly thermally stable compounds, weakening the migration of V₂O₅ within the catalyst pores and the damage of vanadium acid to the catalyst structure. This multifunctional additive, used in catalytic cracking unit, can reduce the dry gas yield by 0.4 percentage point, hydrogen yield by 15.8%, coke yield by 1.09 percentage points, and heavy oil yield by 0.45 percentage point. At the same time, the gasoline yield increased by 2.18 percentage points and the overall light oil yield increased by 2.87 percentage points. It showed good effect of inhibiting nickel and vanadium contamination and improving product distribution.

Key words: fluid catalytic cracking, nickel, vanadium, multifunctional additive