Ce1-xFexO2复合氧化物的结构及其催化碳烟低温燃烧性能

用水热法制备了不同摩尔比的系列Ce1-xFexO2复合氧化物碳烟燃烧催化剂. 采用X射线粉末衍射(XRD)、比表面积(BET)、拉曼光谱(Raman)、H2程序升温还原(H2-TPR)及程序升温氧化反应(TPO)等技术考察了Fe含量对催化剂结构和性能的影响, 重点探讨了催化剂表面性质和体相结构与催化活性和稳定性之间的关系. 结果表明, Fe3+较难进入CeO2晶格中, 部分Fe2O3分散在CeO2表面. 铈铁固溶体(氧空位)有利于氧的吸附活化, 而表面氧化铁对提高催化剂的抗老化能力起着重要作用. Ce0.8Fe0.2O2有最高的Fe3+掺杂量, 有良好分散性的表面Fe2O3, 显示出最好的催化活性和稳定性, 催化碳烟的起燃温度(Ti)和生成CO2的峰值温度(Tp)分别为262和314 ℃. Ce0.8Fe0.2O2高温老化后的Ti和Tp仍较低, 分别为292和392 ℃.

Structure and Catalytic Property of Ce1-xFexO2 Mixed Oxide Catalysts for Low Temperature Soot Combustion

A series of Ce1-xFexO2 mixed oxides with different Ce/Fe molar ratios were prepared via hydrothermal method. The effect of Fe content on structure and porperty of the prepared catalysts were characterized by powder X-ray diffraction (XRD), BETspecific surface area, Raman spectroscopy, and H2 temperature-programmed reduction (H2-TPR) techniques. The performance of the catalysts for soot oxidation was evaluated by temperature-programmed oxidation (TPO). Results showed that Fe3+ did not readily dissolve into the ceria lattice and some Fe2O3 highly dispersed on the surface of ceria. Both the formation of Ce-Fe solid solution created sites (oxygen vacancies) for absorbing and activating oxygen, and the presence of surface Fe2O3 strongly improved the aging resistance of the catalysts. With well dispersed surface Fe2O3 and the largest dopant content, the Ce0.8Fe0.2O2 catalyst had the lowest Ti (262 ℃, ignition temperature of soot oxidation) and Tp (314 ℃, temperature of maximumevolution of CO2). Even after aging for long periods at high temperature, the Ti and Tp values for Ce0.8Fe0.2O2 were still relatively low, at 292 and 392 ℃, respectively, indicating high thermal stability.