Quick X-ray Absorption Fine Structure Studies on the Activation Process of Ni2P Supported on K-USY

Ni2P/K-USY (K-promoted ultrastable Y-type zeolite) is an efficient catalyst for hydrotreatment of petroleum feedstocks. The structural changes of the passivated catalyst during activation were followed by quick XAFS (X-ray absorption fine structure) with online gas analysis. Activation was conducted by temperature-programmed reduction (TPR) from ambient temperature to 773 Kunder a flow of H-2. The Ni species was present as Ni(OH)(2) in the passivated sample. Two peaks were detected by gas analysis during TPR. The quick XAFS analysis revealed that the first peak at 390 K was due to desorption of water from Ni(OH)(2) accompanied by formation of atomically dispersed Ni2+ species. The second peak, observed at 773 K, was due to the regeneration of Ni2P by the simultaneous reductive reaction of the atomically dispersed Ni oxide and the phosphate species, followed by growth of Ni2P nanocrystals. No formation of Ni metallic phase was observed.