Characterization of alumina supported Pd catalysts modified by rare earth oxides using X-ray photoelectron spectroscopy and X-ray diffraction: enhanced thermal stability of PdO in Nd/pd catalysts

摘要

Thernlal stability of palladium oxides on industrially manufactured aluIlllna sup~orted catalysts moQInea Dy l~a, La ana na )xides was investigated using X-ray photoelectron spectroscopy (XPS) and X-ray iliffraction (XRD). Catalysts were prepared )y mechanical mixing of washcoat material with Pd precursor compound. A stepwise thernlal reduction in high vacuum was perfornled in order to investigate the effect of noble metal loading, stabilizers and aging on the thernlal stability of PdO. One )f the pseudo-binary compounds of Nd2O3/PdO, N~PdO7, was successfully manufactured and characterized by XRD and XPS. The presence of N~PdO7 as a sUrface compound was identified by its unusually high binding energy of the Pd 3d5/2 photoelectron peak (337.6 e V). PdO fornled as a result of the decomposition of the alumina supported N~PdO7 upon aging in air at 950°C exhibited clearly higher thernlal stability than pure PdO supported on alumina. La, Ha and Nd oxides were also found to enhance the thernlal stability of PdO.