THE EFFECT OF DRYING CONDITIONS ON COMPOSITION AND DISTRIBUTION OF ACTIVE COMPONENTS IN A NI-MO AL2O3 CATALYST/

It is shown by Raman spectroscopy that, in a Ni-Mo/Al2O3 catalyst, the molybdenum ions form surface polymolybdates and phases of crystalline alpha-NiMoO4 and disordered beta-nickel molybdate. The molybdenum com pounds are deposited mainly in the subsurface layer coating the granul e as a thin ''shell.'' Longer times and higher temperatures of drying favor the migration of molybdenum to the outer surface of the granule. At the same time, the amount of alpha-NiMoO4 decreases due to rearran gement of this phase consequently into beta-NiMoO4, and into Ni-Mo-Al compounds. The amount of storage time between the drying and calcinati on steps does not affect the composition or the distribution of active components.