Reversible Structural Transformation of Palladium Catalyst Supported on La−Al₂O₃ Probed with X-ray Absorption Fine Structure

Abstract

Reversible transformation of the palladium catalyst during thermal cycling was investigated with X-ray absorption fine structure. PdO was transformed to Pd at 850 °C upon when the air temperature was increased while the reverse transformation occurred at 680 °C. On-line TGA/MS measurements combined with EXAFS/XANES showed oxygen generation at 680 °C, indicating that the metal−support interaction stabilizes the catalyst, by transforming to the surface attached PdO and further to Pd metal agglomerates at 850 °C. Thermal stability of the Pd metal agglomerate was also improved by coating the Pd catalyst with TiO2.