Preparation and characterization of Me2O3-CeO 2 (Me = B, Al, Ga, In) mixed-oxide catalysts

Abstract

The present work is focused on the synthesis and characterization of ceria-based mixed oxides. Ceria was combined with the other oxides from group III, with the intention of improving the catalytic properties of thus obtained materials. (B2O3, Al2O3, Ga 2O3, In2O3)-CeO2 mixed oxides with a wide range of Me2O3 contents have been prepared by a coprecipitation route. The obtained solid materials have been characterized in terms of their structural, textural, and surface properties, including the acid-base and red-ox features, by a variety of techniques (BET, XRD, Raman, SEM, TG, TPR-TPO). The acid-base properties were estimated by the adsorption of probe molecules (NH3 and SO2), investigated by the use of two techniques: microcalorimetry and XPS. The obtained materials exhibited satisfactory homogeneity; the highest surface areas were achieved for Al2O3-CeO2 mixed oxides. Only the fluorite structure of CeO2 was observed by XRD for all prepared mixed oxides, along with the presence of oxygen vacancies, which has been proven by Raman spectroscopy. Red-ox properties were investigated for In2O 3-CeO2 samples. The degree of reduction decreased with In2O3 loading. Besides, the reduction-oxidation cycle, performed up to 830°C, changed the morphology and structure of the samples irreversibly, leading to crystallization of In2O3. Among all investigated materials, only boria created significant acidity, whereas the basicity has been found to be dependent on the nature and amount of group III metal. © 2007 American Chemical Society.