Structural, morphological, and surface chemical features of Al2O3 catalyst supports stabilized with CeO2

Two families of CeO2/Al2O3 (ACE) catalyst supports, containing 3 and 20% wt CeO2 respectively, have been examined and compared with the pure oxides CeO2 and (transition-phase) Al2O3. Structural data indicate that, also in the presence of CeO2, the Al2O3 support undergoes all phase transitions at the usual temperatures. Electron micrographs show that particles morphology and crystals size are mainly imposed by the Al2O3 support. The porosimetric texture indicates a more pronounced mesoporosity in the ACE systems than in pure Al2O3, especially in the case of low CeO2 loadings. FTIR spectra and volumetric/calorimetric data of the adsorption of CO at ≈300 K show that the surface Lewis acidity of aluminas is severely modified by the presence of CeO2: the overall CO uptake is increased, there is the formation of one additional family of Lewis acid sites (Ce4+ ions), and the presence of CeO2 either leaves unchanged or increases the concentration of the strongest Lewis centres of (transition-phase) aluminas (Al3+ in tetrahedral coordination).