Comparative study of the hydrogen reduction of Ni2+ ions in X- and Y-zeolites

Abstract

The kinetics of the hydrogen reduction of Ni²⁺ ions in X- and Y-molecular sieves has been studied over a wide range of temperatures. The localization of Ni²⁺ ions before and after their reduction has been determined from X-ray analysis. Ni²⁺ ions can be more easily reduced in X- than in Y-frameworks. In Y-zeolites, it is shown that the reduction of Ni²⁺ ions depends on the initial localization of these cations and the reduction of Ni²⁺ ions located on sites I requires a high activation energy. In X-zeolites the sites appear to be energetically homogeneous and the reduction of Ni²⁺ ions on sites I, I′ and II occurs simultaneously.