Nanoporous CeO2-ZrO2 Oxides for Oxidation of Volatile Organic Compounds

Here, mixed nanostructured ceria/zirconia oxides have been prepared either by wet impregnation on nanostructured ZrO2 or by co-condensation through an evaporation-induced self-assembly (EISA)-derived pathway. This latter method and impregnation on amorphous ZrO2, followed or not by heating at 480 degrees C, lead to a uniform cerium distribution in the zirconia framework, and solid solutions are formed. Stabilization of the tetragonal structure of nano-ZrO(2 )with the increase of the cerium content is observed by X-ray diffraction (XRD) and Raman spectroscopy. The surface Ce/Zr molar ratio determined by X-ray photoelectron spectrometry (XPS) is very close to the bulk one, calculated from the X-ray fluorescence analysis. In contrast to the appearance of nanosized ceria particles with the increase of the cerium content, a monoclinic/tetragonal mixture and enrichment of the surface in cerium are noted if the impregnation is carried out on nanostructured ZrO2 previously calcined at 480 degrees C. The obtained catalysts have been tested for the oxidation of toluene, used as a model volatile organic compound. The catalytic efficiency of the mixed oxides has also been compared to that of pure commercial ceria. Results show that the preparation method has a significant effect on the catalytic properties of the materials. Although pure ceria presents the best activity and selectivity, the nanostructured ZrO(2 )previously calcined at 480 degrees C and impregnated by 10 mol % CeO2 is almost as efficient as pure ceria.