Pd-MnOx/γ-Al2O3 Monolithic Catalysts Prepared by Impregnation Method and Effect of Different Supports on Ground-Level Ozone Decomposition

Pd-MnOx/gamma-Al2O3 catalysts were prepared by impregnating Pd and MnOx on y-Al2O3 supports, using an incipient wetness impregnation method, and then coating on a cordierite substrate to obtain monolithic catalysts. The catalysts were characterized using X-ray diffraction (XRD), temperature-programmed reduction of H-2 (H-2-TPR), low-temperature N-2 adsorption-desorption measurements, and Xray photoelectron spectroscopy (XPS). The effects of the Pd and MnOx impregnation order on the catalytic activity, redox performance, textural properties, and surface electronic characteristics of the catalysts were studied. The experimental results showed that the activity of the catalyst co-impregnated with Pd and MnOx on y-Al2O3 was better than that of the catalyst impregnated sequentially with Pd and MnOx. A synergetic effect was observed between Pd and MnOx on the Pd-MnOx/y-Al2O3 catalysts for ozone decomposition. The effects of various supports on catalytic activity, redox performance, textural properties, and surface electron characteristics of the catalysts were also investigated. The results indicated that the catalytic activities of Pd-MnOx/La-Al2O3 and Pd-MnOx/SiO2 catalysts were the best; ozone conversion reached 82% at 14 degrees C and ozone was completely decomposed at 36 degrees C. The activity of the Pd-MnOx/gamma-Al2O3 catalyst was second better, but the activity of the Pd-MnOx/Zr-Al2O3 catalyst was poor. The support clearly affects the reducibility of PdO and MnOx. The redox performances of MnOx impregnated on different supports followed the order: Pd-MnOx/SiO2>Pd-MnOx/La-Al2O3>Pd-MnOx/gamma-Al2O3>Pd-MnOx/Zr-Al2O3.