Abstract

FINOL, Dora M. et al. Characterization of Pd/Ce_0.8Tb_0.2O_x/La₂O₃-Al₂O₃ by means of Thermal Programmed Reduction (TPR), Thermal Programmed Desorption (TPD) and Thermal Gravimetric Analysis (TGA). Rev. Téc. Ing. Univ. Zulia [online]. 2002, vol.25, n.3, pp.149-157. ISSN 0254-0770.

Abstract     A Pd/Ce_0.8Tb_0.2O_x/La₂O₃-Al₂O₃ catalyst was prepared and characterized by using TPD of H₂ and O₂, TPR and TGA measurements. Pd/CeO₂ and Pd/Al₂O₃ catalysts were used as reference samples. Pd/Ce_0.8Tb_0.2O_x/La₂O₃-Al₂O₃ and Pd/Al₂O₃ catalysts showed a deactivation with the increase of the reduction temperature, specially at 700°C. The Pd/Ce_0.8Tb_0.2O_x/La₂O₃-Al₂O₃ catalyst had irreversible changes when it is heated at high temperatures (900°C). The studies of TPR showed that the Pd is reduced in two steps, and that the Pd/Ce_0.8Tb_0.2O_x/La₂O₃-Al₂O₃ catalyst is reduced in a larger interval of temperature than the Pd/CeO₂ catalyst. In the TGA diagrams of Pd/Ce_0.8Tb_0.2O_x/La₂O₃-Al₂O₃ and Pd/Al₂O₃ catalysts, was observed the existence of hysteresis in the redox couple PdO « Pdº. These results, in good agreement with the TPD-O₂ ones, showed that in the supported mixed oxide of Ce/Tb the palladium oxidation occurs at higher temperatures than in the Pd/Al₂O₃ catalyst.

Keywords : Three way catalysts; TPD - H₂, TPD - O₂; TPR and TGA..