THE SURFACE REACTIVITY OF DIFFERENT ALUMINAS AS REVEALED BY THEIR XPSCLS SPECTRA

Aluminium oxides were prepared from different starting materials and b y different methods. All aluminas were calcined at 873 K and an alumin a gel precursor was heated to various temperatures in the range 373-12 73 K. Analysis of the XPS C1s spectra, derived from adsorbed atmospher ic hydrocarbons, indicated the presence of varying proportions of diff erent carbonaceous species. A systematic variation was observed for th e heat treated gel precursor. XRD results, for the aluminas calcined a t 873 K. could not be correlated with the observed differences. The re sults are interpreted as being due to changes in the properties of act ive surface sites which depend on sample history and thermal treatment . The XPS C1s spectra also showed that the predominant hydrocarbon rea ction was dehydrogenation and that this could be used to characterise the activity of the aluminas. It is proposed that analysis of C1s spec tra may be extended to provide a useful method for characterising the surface properties of other oxidic materials.