In situ NiK-edge XANES study of the reducibility of Ni in FCC catalysts

The majority of the Ni in an aged equilibrated catalyst (ECAT) from the resid UOP fluid catalytic cracking (FCC) unit in the Pertamina EXOR-1 refinery (with 12,000 ppm Ni) is present primarily as a NiAl2O4 phase. No appreciable Ni reduction occurs below 500 degrees C in a flow of H-2. In situ Ni K-edge XANES has been used to follow the reduction kinetics of this NiAl2O4 phase. Reduction in Ha is described by pseudo-second-order kinetics. An apparent activation energy is estimated to be 26 kcal/mol. This value is compared to that of 4.3 kcal/mol for NiO reduction and 32 kcal/mol for NiAl2O4 reduction. Less than 10% of the Ni is estimated to go through a redox cycle in an FCC unit, resulting in a negligible impact on the hydrogen in coke calculation.