Zirconia–alumina mixing in alumina-supported zirconia prepared by impregnation with solutions of zirconium acetylacetonate

Materials containing 2–20 wt% zirconia supported on γ-alumina were prepared by multiple step incipient wetness impregnation with solutions of zirconium acetylacetonate in benzene. The materials were calcined at 823 K and were characterised by X-ray diffraction, XPS, DRS in the UV-visible region and FTIR in the regions of OH stretching and skeletal vibrations of adsorbed pyridine. The results demonstrated that the zirconium is present as isolated species at the surface and in the bulk of a mixed zirconia–alumina phase formed by migration of the zirconium ions into the subsurface layers of the support. The presence of zirconia at the alumina surface caused the appearance of basic hydroxyl groups bonded to a single zirconium ion, of weak Lewis acidic sites, probably associated with zirconium sites, and a decrease in concentration of stronger Lewis sites associated with the alumina surface.