Abstract
Supported ceria and lanthana catalysts on alumina and silica were prepared by impregnating two different supports (SiO2 and Al2O3) with an aqueous solution of lanthanum nitrate or diammonium hexanitratocerrate, to yield final materials containing 3 and 10wt.% of CeO2 or La2O3 catalysts. The products thus obtained were calcined at 650°C for 2h in static air for supported La2O3 catalysts and at 500°C for 2h for supported ceria catalysts. X-ray powder diffractograms and nitrogen adsorption isotherms (at −196°C) obtained on the support and supported catalysts were investigated. The pore volume was calculated from the adsorption branch to explore the modification of the porosity of unsupported and supported catalysts. The results suggest formation of highly dispersed lanthana on the surfaces of alumina and silica up to 10wt.%, leading to pore narrowing. In contrast, a poor dispersion of ceria on alumina (higher than 3wt.%) and silica (at 3wt.%) in the form of small CeO2 crystallites was observed and found to lead to pore blocking. These conclusions can be rationalized on the basis of the different surface chemical properties of the oxide supports and nature of oxide supported. It is revealed that nitrogen adsorption data offer valuable qualitative information on the dispersion of supported oxide materials.
Published Version
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