浸渍法制备的Pd-MnO_x/γ-Al_2O_3催化剂及不同载体对地表O_3降解的影响(英文)

在γ-Al2O3载体上用等体积浸渍法浸渍Pd、MnOx活性组分,然后涂覆于堇青石基体上制备Pd-MnOx/γ-Al2O3整体式催化剂.分别用X射线衍射(XRD)、H2-程序升温还原(H2-TPR)、低温N2吸附-脱附及X射线光电子能谱(XPS)对制备的催化剂进行表征.研究了Pd、MnOx浸渍顺序对催化剂活性、氧化还原性能及织构性质的影响.实验结果表明,Pd、MnOx共浸渍较分别浸渍制备的催化剂活性好,Pd和MnOx之间存在一定的协同作用.考察了不同载体如La-Al2O3、SiO2、γ-Al2O3和Zr-Al2O3对催化剂活性、氧化还原性能、织构性质及表面电子性能的影响.研究表明,以La-Al2O3或SiO2为载体的催化剂活性最好,即,14°C时O3转化率为82%,完全转化温度为36°C.γ-Al2O3载体次之,Zr-Al2O3载体较差.不同载体制备的催化剂中MnOx的氧化还原性能顺序为:PdMnOx/SiO2Pd-MnOx/La-Al2O3Pd-MnOx/γ-Al2O3Pd-MnOx/Zr-Al2O3.

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

Pd-MnO_x/γ-Al₂O₃ catalysts were prepared by impregnating Pd and MnO_x on γ-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), temperatureprogrammed reduction of H₂ (H₂-TPR), low-temperature N₂ adsorption-desorption measurements, and Xray photoelectron spectroscopy (XPS). The effects of the Pd and MnO_x 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 MnO_x on γ- Al₂O₃ was better than that of the catalyst impregnated sequentially with Pd and MnO_x. A synergetic effect was observed between Pd and MnO_x on the Pd-MnO_x/γ-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-MnO_x/La-Al₂O₃ and Pd-MnO_x/SiO₂ catalysts were the best; ozone conversion reached 82% at 14 ℃ and ozone was completely decomposed at 36 ℃. The activity of the Pd-MnO_x/γ-Al₂O₃ catalyst was second better, but the activity of the Pd-MnO_x/Zr-Al₂O₃ catalyst was poor. The support clearly affects the reducibility of PdO and MnO_x. The redox performances of MnO_x impregnated on different supports followed the order: Pd-MnO_x/SiO₂>Pd-MnO_x/La-Al₂O₃>Pd-MnO_x/γ-Al₂O₃>Pd-MnO_x/Zr-Al₂O₃.