Yang Xiao, Wang Xiaofei, Qiao Xiaolei, Jin Yan, Fan Baoguo
College of Electrical and Power Engineering, Taiyuan University of Technology, Yingze West Street 79, Taiyuan 030024, China.
Materials (Basel). 2020 Feb 17;13(4):888. doi: 10.3390/ma13040888.
Cu-ZSM-5 and Ce-doped Cu-Ce-ZSM-5 samples were prepared by liquid-phase ion exchange method. The two catalysts were subjected to hydrothermal aging treatment in the simulated flue gas of a coal-fired power station at an ageing temperature of 650-850 °C. The denitration experiment found that the activity of the aged Cu-ZSM-5 was 19.6% to 41% lower than that of the fresh Cu-ZSM-5 at the optimal decomposition temperature of NO at 550 °C, while the aged Cu-Ce-ZSM-5 had only a 14.8% to 31.5% reduction in activity than the fresh Cu-Ce-ZSM-5. The samples were characterized by XRD, BET, H-TPR, XPS, NO-TPD, etc. The results showed that hydrothermal aging treatment leads to the dealumination of the ZSM-5 framework and reduces the specific surface area and pore volume of the micropore in the sample. It also exacerbates the isolated Cu, and the active center {Cu-O-Cu} dimers migrate towards the sample surface and form inactive CuO. Doping with Ce can promote the dispersion of Cu(OH), which was the precursor of {Cu-O-Cu}. Ce can preferentially occupy the less active bridged hydroxyl exchange sites, so that copper ions occupy the more active aluminum hydroxyl sites, thereby inhibiting the migration of active centers.
采用液相离子交换法制备了Cu-ZSM-5和Ce掺杂的Cu-Ce-ZSM-5样品。将这两种催化剂在650-850℃的老化温度下于燃煤电站的模拟烟气中进行水热老化处理。脱硝实验发现，在550℃的NO最佳分解温度下，老化后的Cu-ZSM-5的活性比新鲜的Cu-ZSM-5低19.6%至41%，而老化后的Cu-Ce-ZSM-5的活性仅比新鲜的Cu-Ce-ZSM-5降低了14.8%至31.5%。采用XRD、BET、H-TPR、XPS、NO-TPD等对样品进行了表征。结果表明，水热老化处理导致ZSM-5骨架脱铝，降低了样品中微孔的比表面积和孔体积。它还加剧了孤立的Cu的情况，活性中心{Cu-O-Cu}二聚体向样品表面迁移并形成无活性的CuO。掺杂Ce可以促进{Cu-O-Cu}的前驱体Cu(OH)的分散。Ce可以优先占据活性较低的桥连羟基交换位点，使铜离子占据活性较高的铝羟基位点，从而抑制活性中心的迁移。
