Investigation of nickel species on commercial FCC equilibrium catalysts - implications on catalyst performance and laboratory evaluation

Several commercial FCC equilibrium catalyst (ECAT) samples were examined by X-ray photoelectron spectroscopy (XPS) in an effort to characterize the nickel contaminants. It was found that the majority of the nickel was present as NiAl2O4 or Ni2SiO4 (cannot differentiate with XPS), with a small percentage as NiO. There was little difference in the relative amounts of each on the ECAT samples. Variations in the surface concentration of the nickel could be used to explain the coke and hydrogen selectivity differences of the ECAT samples. Compared to laboratory prepared references with fresh nickel, the degree of surface enrichment for the ECAT samples was much lower. This suggests that catalyst technologies that promote low surface concentrations of nickel offer better performance in the presence of nickel. Additionally, we examined fresh catalyst samples that were impregnated with nickel and deactivated using cyclic propylene steaming (CPS). These samples looked very much like commercial ECAT using XPS. However, selectivity testing suggested that the nickel on these CPS samples may be slightly more active than on ECAT. (C) 1998 Elsevier Science B.V.