Surface properties of CeZrO4-based materials employed as catalysts supports

The surface properties of high surface area CeZrO4, 10 Wt.% CeZrO4/gamma -A l2O3, and 33 wt.% CeZrO4/gamma -Al2O3 samples, prepared by a reverse microe mulsion synthesis method, have been studied by FTIR and EPR, employing, res pectively, CH3OH and O-2 as probe molecules. Observation of on-top methoxy species adsorbed both on Zr4+ and Ce4+ (C-O stretching bands appearing at, respectively, ca. 1156 and 1104 cm(-1)) upon methanol adsorption on the out gassed samples and the red shift of the former with respect to pure zirconi a or ZrO2/Al2O3 evidences the presence of a mixed oxide type structure at t he surface of the samples. EPR analysis of O-2(-) species generated upon O- 2 adsorption on the outgassed samples reveals the presence of both disperse d (2D) and aggregated (3D) mixed oxide entities in Al2O3-supported samples. Redox differences between these entities have been revealed, 2D entities s howing a higher reducibility while they are more difficult to be oxidised. Differences in the surface redox and structural properties of 3D particles on alumina with respect to unsupported CeZrO4 are attributed to an epitaxia l relationship between the small size (ca. 2-3 nm) 3D mixed oxide particles and the alumina surface. (C) 2001 Elsevier Science B.V. All rights reserve d.