| dc.description.abstract | MnOx-CeO2 was reported to be active for VOCs combustion and Pd/CeO2 were reported to be very active to destruct toluene from this lab. Therefore, combination of MnOx-CeO2 and palladium is a potential candidate to achieve a catalyst with high activity. In this study, a series of Pd/MnOx-CeO2 catalysts with various ratios of Mn/(Mn + Ce) were prepared. MnOx-CeO2 supports were prepared by co-precipitation method and redox-precipitation method, Pd was loaded by incipient-wetness impregnation method. The Pd loadings in all samples were fixed at 0.5 wt.%. The catalysts were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction (TPR). The catalysts were tested for total oxidation of toluene. The feed concentration of toluene was 8.564 g/m3 (2085 ppm), with GHSV= 10,000 h-1. The TEM and HRTEM images showed that Pd particle sizes were 3–5 nm and well-dispersed on the support. This result is consistent with the XRD studies. XPS study indicated that the suitable ratio of Mn/(Mn + Ce) able increased the proportion of metallic palladium, the content of high valance state manganese and the catalytic activity. Redox-precipitation prepared MnOx-CeO2 supports have a larger pore volume, surface area, higher manganese valance state, and higher surface manganese amount compare with MnOx-CeO2 prepared by CP method. Moreover MnOx-CeO2 prepared by RP method had a special tube-like shape, so that Pd/MnOx-CeO2 RP had a higher activity. Pd/MnOx-CeO2 catalyst was better than the physically-mixed Pd/MnOx and Pd/CeO2 catalyst, which indicates that there is a strong interaction between ceria and manganese. In conclusion, Pd/MnOx-CeO2 catalysts were superior to Pd/MnOx and Pd/CeO2 catalysts due to the synergetic effect between Ce and Mn. Pd/MnOx-CeO2 catalysts are very promising for toluene destruction.
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