CeWTi催化剂脱硝性能的研究

Activity and Characterization of CeWTi Catalysts for the Selective Catalytic Reduction of NO with NH

采用浸渍法合成不同CeO2含量的CeWTi催化剂,通过XRD、N2吸附-脱附、XPS、H2-TPR和NH3-TPD等表征对催化剂的结构及性能进行了研究。结果表明,随着CeO2含量的增加,TiO2结晶化程度降低,且TiO2和CeO2保持一定的结晶度有利于催化剂脱硝性能的提高;CeO2和WO3之间强的相互作用和催化剂界面处活性氧数量对SCR活性影响较大;随着CeO2含量的增加,弱吸附氨物种数量整体呈增加趋势,强吸附氨物种的数量呈先增加后降低的趋势,其中化学吸附的NH3物种数量增多且稳定性增强有利于脱硝性能的提高;孔径分布较集中且适当小的平均孔径和孔体积、表面适当的Ce3+含量和吸附氧物种有利于SCR性能的提高。通过SCR性能测试,CeO2的含量对CeWTi催化剂的脱硝性能影响较大,其中20CeWTi催化剂具有最佳的NH3-SCR活性,其在250℃时NOx的转化率接近60%,300℃~450℃范围内NOx转化率达90%以上。

In this study, a series of CeWTi catalysts was prepared by impregnation method in order to explore influence of the CeO2 contents on catalytic performance. The structure and properties of the catalysts were characterized by XRD, N2 adsorption-desorption, XPS, H2-TPR and NH3-TPD. Characterizations revealed that the degree of crystallization of TiO2 decreased as the content of CeO2 increasing, and maintaining a certain degree of crystallinity of TiO2 and CeO2 was contribute to the improvement of the SCR performance of the catalyst. The strong interaction between CeO2 and WO3 and the amount of active oxygen at the interface had a greater impact on SCR activity. The number of weakly adsorbed ammonia species generally increased and strongly adsorbed ammonia species increased first and then decreased with the increasing of CeO2 content.The excellent catalytic performance might be attributed to the increase amounts and improved stability of chemically adsorbed NH3.Besides,the relatively concentrated distribution of pore size, the appropriately small pore size and volume, as well as the appropriate amount of Ce3+ and adsorbed oxygenon surface were also beneficial to improve the performance. Through the SCR performance test, we found that the different content of CeO2 had a greater impact on the SCR performance.Particularly, 20 CeWTi showed excellent NH3-SCR activity,the NOx conversion was close to 60% at 250 ℃ and maintained more than 90% from 350 to 450 ℃.