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 res id 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 appreciab le Ni reduction occurs below 500 degrees C in a flow of H-2. In situ Ni K-e dge XANES has been used to follow the reduction kinetics of this NiAl2O4 ph ase. Reduction in Ha is described by pseudo-second-order kinetics. An appar ent activation energy is estimated to be 26 kcal/mol. This value is compare d to that of 4.3 kcal/mol for NiO reduction and 32 kcal/mol for NiAl2O4 red uction. 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 calc ulation.