Redox behaviour of transition metal ions in zeolites. Part 7.—Characterization of a nickel metal phase in zeolite NaY

Abstract

NiY zeolite has been treated under steaming and non-steaming conditions and reduced in hydrogen at different temperatures. In the solids obtained this way, the Ni(O) metal phase was characterized by temperature programmed reduction and oxidation techniques and by ferromagnetic resonance spectroscopy.

Both techniques show that a bidispersion of metal particle sizes exists. The size of the particles inside the zeolite is restricted to the dimensions of the supercage. For samples reduced at elevated temperatures, small particles are found in structural defects of the crystals. In each case, the Ni metal particles either strongly interact with the support or are incompletely reduced.

Large Ni metal particles are formed outside the zeolite. They are completely reduced and do not interact with the support. They are ellipsoidal since they exhibit shape anisotropy.