Investigation of the regeneration of NiMoP/Al2O3 hydrotreating catalysts

A NiMoP/Al(2)O(3 )catalyst deactivated at the industrial plant was subjected to oxidative regeneration and reactivation with water and an aqueous solution of citric acid. The catalyst was studied at all stages by XRD, UV-vis, Raman spectroscopy, FTIR spectroscopy, XPS and HRTEM methods. The catalyst samples after oxidative regeneration, treatment with water and rejuvenation with citric acid were tested in hydrotreatment of the model feedstock and straight-run gasoil. It was established that the regenerated catalyst contained phosphorus strongly bound to the support and soluble or insoluble Ni and Mo compounds. The catalyst after water treatment contained only insoluble Ni and Mo compounds and a phosphate monolayer, while treatment with citric acid resulted in the formation of citrate complex compounds. Ni and Mo compounds in the sulfide form, which were obtained from insoluble components, showed high activity in the target hydrotreating reactions.