Redox behavior of CeO2-ZrO2 mixed oxides - II. Influence of redox treatments on low surface area catalysts

Redox and textural/structural properties of low surface area (LS) ceria-zir conia mixed oxides with composition ranging from 0 to 85 mol% of ZrO2, have been studied using Raman spectroscopy, X-ray diffraction, textural charact erization, magnetic susceptibility measurements, temperature-programmed red uction and oxidation and buffering measurements. Special attention was give n to the effects of aging under redox conditions. Correlation between chemi cal composition, textural, structural and redox properties of the oxides is reported. Comparison with previously reported high surface area (HS) sampl es shows that in spire of the initial low surface area of the present sampl es (approximate to 20 versus approximate to 100 m(2) g(-1)), the reduction occurs at fairly low temperatures when zirconium is incorporated into the C eO2 lattice. Remarkably, the favorable effects of the redox-aging on the re duction behavior are more pronounced in the present LS samples compared to the previously investigated HS ones. Raman and X-ray investigations reveale d that important modifications of the structure take place as a consequence of the redox aging, leading to appreciable CeO2 segregation, which could s uggest some correlation between these parameters. (C) 2001 Elsevier Science B.V. All rights reserved.