MO-USY ZEOLITES FOR HYDRODESULFURIZATION .1. STRUCTURE AND DISTRIBUTION OF MOLYBDENUM OXIDE PHASE

Ultrastable (USHY) zeolite has been used as a support material for a series of molybdenum catalysts prepared using various precursors and activation procedures. Studies using atomic absorption spectroscopy, X-ray photoelectron spectroscopy, Fourier transform IR of the mid-infrared range and of adsorbed nitric oxide and pyridine, and sorption capacity of water indicate that the distribution of molybdena in the zeolite is strongly influenced by the preparation procedures. Catalysts calcined by a non-conventional procedure, involving decomposition of the precursor by heating under vacuum over extended periods of time, show a migration of the molybdena from the external surface into the lattice cavities.