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FeOx-CeO2 mixed oxides with increasing Fe/(Ce+Fe) atomic ratio (1-20 mol%) were prepared by sol-gel method and characterized by X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET) and Hydrogen temperature-programmed reduction (H2-TPR) techniques. The dynamic oxygen storage capacity (DOSC) was investigated by mass spectrometry with CO/O2 transient pulses. The powder XRD data following Rietveld refinement revealed that the solubility limit of iron oxides in the CeO2 was 5 mol% based on Fe/(Ce+Fe). The lattice parameters experienced a decrease followed by an increase due to the influence of the maximum solubility limit of iron oxides in the CeO2. TPR analysis revealed that Fe introduction into ceria strongly modified the textual and structural properties, which influenced the oxygen handling properties. DOSC results revealed that Ce-based materials containing Fe oxides with multiple valences contribute to the majority of DOSC. The kinetic analysis indicated that the calculated apparent kinetic parameters obey the compensation effect. The three-way catalytic performance for Pd-only catalysts based on the Fe doping support exhibited the redundant iron species separated out of the CeO2 and interacted with the ceria and Pd species on the surface, which seriously influenced the catalytic properties, especially after hydrothermal aging treatment.  相似文献
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Copper-exchanged chabazite(Cu/CHA) catalysts have been found to be affected by alkali metal and alkaline earth ions. However, the effects of Na~+ ions on Cu/SAPO-34 for ammonia selective catalytic reduction(NH_3-SCR) are still unclear. In order to investigate the mechanism, five samples with various Na contents were synthesized and characterized. It was observed that the introduced Na~+ ion-exchanges with H+and Cu~(2+)of Cu/SAPO-34. The exchange of H+is easier than that of isolated Cu~(2+). The exchanged Cu~(2+)ions aggregate and form "CuAl_2O_4-like" species.The NH_3-SCR activity of Cu/SAPO-34 decreases with increasing Na content, and the loss of isolated Cu~(2+)and acid sites is responsible for the activity loss.  相似文献
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