Preparation and Characterization of Me₂O₃−CeO₂ (Me = B, Al, Ga, In) Mixed-Oxide Catalysts

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. (B 2 O 3, Al 2 O 3, Ga 2 O 3, In 2 O 3 )−CeO 2 mixed oxides with a wide range of Me 2 O 3 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 (NH 3 and SO 2 ), investigated by the use of two techniques: microcalorimetry and XPS. The obtained materials exhibited satisfactory homogeneity; the highest surface areas were achieved for Al 2 O 3 −CeO 2 mixed oxides. Only the fluorite structure of CeO 2 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 In 2 O 3 −CeO 2 samples. The degree of reduction decreased with In 2 O 3 loading. Besides, the reduction−oxidation cycle, performed up to 830 °C, changed the morphology and structure of the samples irreversibly, leading to crystallization of In 2 O 3 . 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.