Effect of Ce3+ ions exchanged in NiX zeolites on the location and reducibility of Ni2+ ions and on the stabilization of a highly dispersed metallic nickel

Abstract

Highly dispersed nickel particles, with diameters ranging from 0.7 to 3 nm, can be obtained by hydrogen reduction of Ni²⁺ ions exchanged in X zeolites, in the presence of Ce³⁺ ions. Samples with various Ce³⁺/Ni²⁺ ratios have been studied.

The structure and surface properties of the solids were investigated by X-ray diffraction and e.p.r. The particle size was determined by magnetic methods.

It is shown that the Ce³⁺/Ni²⁺ ratio influences the initial location of the Ni²⁺ ions in the different cationic sites and the redox properties of the zeolite.

The effect of Ce³⁺ ions on the obtention of highly dispersed metallic nickel is discussed in terms of strong electrostatic field and electron-donor properties associated with Ce³⁺ ions.