ИСТИНА

The present work is focused on the synthesis and characterization of ceria-niobia mixed oxides. Mixed oxides with a wide range of niobia content were prepared by coprecipitation method with the aim to obtain given acid-base characteristics and subsequently to investigate the catalytic properties of the obtained materials. The synthesized solids 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 spectroscopy, TG, and TPR-TPO). The acid-base properties were estimated by adsorption microcalorimetry measurements of ammonia and sulfur dioxide. All obtained mixed oxides showed specific amphoteric character influenced by relative amounts of the two component oxides. The obtained materials exhibited satisfactory homogeneity; the highest surface area was achieved for sample containing 73 wt % of CeO2. Only the fluorite structure of CeO2 was observed by XRD for all prepared mixed oxides. The crystallinity of samples decreased with increasing amount of Nb2O5. TPR-TPO results were strongly dependent on the bonding nature between the two oxides. In conclusion it was possible to tune the number of surface active sites by varying the ratio of ceria to niobia.