Analytical Sciences

Direct Detection of a Phase Change in PdO/CeO₂ Supported on χ-Al₂O₃ by Means of in situ High-Temperature Measurements of XRD and FTIR

Eiji KANEZAKI,* Suminori TANAKA,** Kei-ichiro MURAI,* Toshihiro MORIGA,* Junko MOTONAKA,* Masahiro KATOH,* and Ichiro NAKABAYASHI*

*Department of Chemical Science and Technology, Faculty of Engineering, The University of Tokushima, 2-1 Minami-Josanjima, Tokushima 770-8506, Japan
**Okura Industrial Co. Ltd., 1515 Nakatsu, Marugame, Kagawa 763-8508, Japan

Phase changes between PdO and Pd metal can be directly detected in PdO/CeO₂ catalysts supported on χ-Al₂O₃ by means of in situ high-temperature measurements of X-ray diffraction and FT-IR in relation to the catalytic activity for the methane oxidation of microcrystalline PdO. Reversible changes in the solid phases are observed from PdO to Pd and Pd to PdO under O₂-deficient and O₂-excess atmospheres, respectively. Nanosizes of PdO and Pd crystallites, the distorted PdO crystal structure along the (110) plane, and also a distorted Pd metal crystal structure along the (200) plane as well as the large surface area elucidate the high catalytic activity for the methane oxidation of PdO/CeO₂ catalysts prepared with an atomic ratio of Pd:Ce = 1:1.

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