Y对柴油车碳烟氧化催化剂MnOx-CeO2热稳定性的影响

采用共沉淀法制备了不同Y含量的MnOx-CeO2-Y2O3催化剂,并用于NOx存在条件下的碳烟氧化反应.通过在干空气气流中800°C焙烧12 h评价了这些催化剂的热稳定性.采用X射线衍射、N2吸附-脱附、拉曼光谱、H2程序升温还原、储氧量测试、NO程序升温氧化、X射线光电子能谱和碳烟程序升温氧化等手段对催化剂进行了表征.实验发现,Y的添加导致催化剂比表面积、还原性能和储氧能力下降,从而影响了NO和碳烟的氧化活性.然而,热老化之后, Y可增大催化剂的热稳定性,其中以6%–10%Y的添加效果最好,它们的最大碳烟氧化速率温度仅增加了34–35°C. MnOx-CeO2催化剂的催化活性和热失活与其表面的Mn4+和氧物种密切相关.

Effect of Y on improving the thermal stability of MnOx-CeO2 catalysts for diesel soot oxidation

A series of MnOx-CeO2-Y2O3 catalysts with different Y loadings (0, 1, 3, 6, and 10 wt%) were pre-pared by a co-precipitation method and investigated for NOx-assisted soot oxidation. The thermal stabilities of these catalysts were evaluated by treating them at 800 °C for 12 h under dry air flow. The catalysts were characterized by X-ray diffraction, N2 adsorption-desorption, Raman spectros-copy, H2 temperature-programmed reduction, oxygen storage capacity, NO temperature-pro-grammed oxidation, X-ray photoelectron spectroscopy, and soot temperature-programmed oxida-tion. The addition of Y led to decreased BET surface areas and poor low-temperature reduction abilities and oxygen storage capacities, which affected NO and soot oxidation activities. However, after aging, the doping of Y had effectively enhanced the stability of the catalytic activities for NO and soot oxidations, where the addition of 6%–10%Y achieved the optimum result because the maximal soot oxidation rate temperature was increased by only 34–35 °C. Additionally, the catalytic activity and deactivation of MnOx-CeO2-containing catalysts were closely related to the presence of Mn4+and oxygen species on the surface.