Joint studies by X-ray photoelectron spectroscopy and analytical electron microscopy of the dispersion of nickel oxide supported on silica and silica–aluminas

Abstract

The dispersion of nickel oxide, NiO, supported on a series of silica and silica–alumina carriers covering the range 100–0 % SiO₂ has been investigated by photoelectron spectroscopy (X.p.s.) and analytical electron microscopy (a.e.m.). The results show that according to the nature of the support, two situations may arise: (1) With NiO on SiO₂, the active phase is present as badly dispersed NiO aggregates. No surface compound or dispersed phase can be detected. (2) With NiO on SiO₂–Al₂O₃, the supported phase exists in two forms: NiO aggregates and a dispersed phase. Increasing the Al₂O₃ content of the carrier leads to an increase in the concentration of the dispersed phase and a decrease in the average size of NiO aggregates.

The results were interpreted on the basis of the interaction between the nickel salt precursor and the support during impregnation and heat treatment.