Abstract: The mechanical mixtures of silica or alumina with NiO, impregnated silica or alumina with Ni sources, together with 5 fresh FCC catalysts and 10 commercial FCC equilibrium catalysts (ECAT) were characterized by XRD to investigate the nickel species on FCC catalyst. The results show that for the samples of NiO mechanically mixed with silica or alumina, NiO was reliably detected when Ni content is higher than 519 μg/g or 694 μg/g, respectively. Compared with the impregnated alumina, NiO can be detected at low Ni contamination content on the impregnated SiO2. As to the alumina impregnated, NiO cannot be detected until the Ni contamination content is over 117 900 μg/g. No NiO can be observed until the Ni content is higher 15000μg/g and 700-2 500 μg/g for fresh FCC catalysts and ECATs, respectively.

Key words: catalytic cracking, spent FCC catalyst, nickel species, XRD