Characterization of Sr²⁺/La₂O₃ catalyst modified with different cobalt content

Cobalt oxide content and calcination temperature effects on the Sr²⁺/La₂O₃ catalyst structure were studied. The Co/Sr - La catalysts were prepared by successive immersion impregnation and characterized by XRD, FTIR, TGA, surface area (B.E.T.) and TPR. The Sr²⁺/La₂O₃ catalysts with low cobalt composition show a strong interaction of Co with the intrinsic La₂O₃ surface defects probably leading to formation of a brownmillerite superstructure, oxygen deficient (LaCoO_3-λ), enriched with Co²⁺ ions. Cobalt contents higher than 2% gave local or island La_1-xSr_xCoO₃ solid solutions and further cobalt addition favors mixed La - Co perovskite-type oxide and cobalt oxide formation. The mixed La - Co oxide is the predominant product when Sr²⁺ is present as an additive. Higher calcination temperatures favor the mixed oxide formation in all the Co composition.