Effect of Hydrothermal Aging Treatment on Decomposition of NO by Cu-ZSM-5 and Modified Mechanism of Doping Ce against This Influence

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...

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Bibliographic Details
Main Authors: Xiao Yang, Xiaofei Wang, Xiaolei Qiao, Yan Jin, Baoguo Fan
Format: Article
Language:English
Published: MDPI AG 2020-02-01
Series:Materials
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Online Access:https://www.mdpi.com/1996-1944/13/4/888
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Summary: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&#8722;850 &#176;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 &#176;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<sub>2</sub>-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<sup>2+</sup>, and the active center {Cu<sup>2+</sup>-O<sup>2&#8722;</sup>-Cu<sup>2+</sup>}<sup>2+</sup> dimers migrate towards the sample surface and form inactive CuO. Doping with Ce can promote the dispersion of Cu(OH)<sup>+</sup>, which was the precursor of {Cu<sup>2+</sup>-O<sup>2&#8722;</sup>-Cu<sup>2+</sup>}<sup>2+</sup>. Ce<sup>3+</sup> 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.
ISSN:1996-1944