水热温度对纳米Cr_(2)O_(3)/CeO_(2)复合氧化物低温催化氧化NO性能的影响

Effect of different hydrothermal temperatures on catalytic performance for NO oxidation at low temperature over nanostructured Cr_(2)O_(3)/CeO_(2)

采用一锅水热法合成了纳米颗粒状铬铈复合氧化物(Cr_(2)O_(3)/CeO_(2)),并将其应用于催化氧化烟气脱硝(SCO),考察了不同水热温度对催化剂低温催化活性的影响.结果表明,当水热温度为180℃时制得的催化剂(CC180)具有较高的低温SCO活性,其在200℃下NO氧化率高达59%.采用X-射线衍射、透射电镜、X-光电子能谱、程序升温脱附等表征手段探讨了催化剂的结构形貌与催化活性之间的构效关系.结果表明,Cr物种主要以表面分散的形式存在于催化剂表面,同时适中的水热温度利于活性位点Cr物种的表面高分散,提升活性位点数量,而催化剂表面较高的六价铬Cr^(6+)和化学吸附氧O_(β)含量则提升了低温下NO和O_(2)的吸附容量,促进了低温下的NO氧化效率.此外,催化剂较高的稳定性及较强的抗硫抗水测试后自恢复性推进了SCO技术的工业化进程.

The Cr_(2)O_(3)/CeO_(2)composites were synthesized via a one-pot hydrothermal method, and were evaluated for denitration on catalytic oxidation of NO(SCO). The influence of different hydrothermal temperatures on catalytic performance at low temperature was investigated. The results showed that the sample with hydrothermal temperature of 180 ℃(CC180) displayed the highest activity among all samples, which exhibited 59% oxidation efficiency at 200 ℃. Kinds of characterizations such as X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption, et al. were applied to explore the relationship between the structure and the activity over the catalysts. The results displayed that Cr species mainly existed on the surface of catalysts in the form of surface dispersion, and the proper temperature of hydrothermal process benefits for the well dispersion of Cr species. The high ratios of Cr^(6+)and chemisorbed oxygen(O_(β)) on the surface promoted the adsorption capacity of NO and O_(2) at low temperature, thus enhancing the NO oxidation efficiency at low temperature. Moreover, the high stability and the strong recovery capacity after the remove of SO;and H;O of this series catalysts promoted the industrial application progress of SCO technology.