Passivation of vanadium in an equilibrium FCC catalyst at short contact-times

An equilibrium FCC (ECAT) sample containing 2800 ppm vanadium and 2500 ppm nickel was characterized by ESR and ESCA, and tested in a microactivity test (MAT) to study the effect of reductive pretreatments at elevated temperatures. From ESR and ESCA studies, it is found that the vanadium of the ECAT sample consists of V4+ converting to a considerable part of V3+ after a treatment with 5% H2 in N2 between 650 and 750 °C. Approximately, 40% of the vanadium exists as V3+ after such a treatment at 700–750 °C. The reductive procedure led to an increase in the gasoline yield and a reduction in the coke yield in MAT when processing an atmospheric residue from the North Sea at 524 °C. It is shown that it is sufficient with a reduction/passivation time as short as 3 min in hydrogen at 689 °C to obtain a significant effect on the gasoline and coke yields. The results indicate that the main part of the observed reduction occurs in the outer layer of the particle at such short reduction times.