Ce、Zr共掺杂提高Cu-ZSM-5催化分解NO性能及抗K中毒能力

Improving performance of Cu-ZSM-5 catalytic decomposition of NO and resistance to K-poisoning by Ce and Zr co-doping

  • 摘要: 将NO在Cu-ZSM-5催化剂的作用下直接分解为环保、清洁的N2和O2是最具经济效益的脱硝手段。高温烟气中存在大量的碱金属,但碱金属会使催化剂催化活性降低、使用寿命大大缩短,并使催化剂造成不可逆的失活。通过离子交换法制备MZ5催化剂(M=Cu、Ce、Zr、CuCe、CuZr、CuCeZr),采用初湿浸渍法将K离子负载到MZ5催化剂。脱硝实验结果表明:在最佳反应温度550℃下,相比于CuZ5,CuCeZrZ5催化剂的NO转化率由原来的53%提高到58%,KCuCeZrZ5催化剂的NO转化率由53%降到52%;相比于KCuZ5,KCuCeZrZ5催化剂的NO转化率由39%提高到52%。采用ICP、SEM、XRD、BET、XPS、H2-TPR和O2-TPD等表征手段对催化剂元素含量、微观形貌、骨架结构、孔隙规律、铜物种种类、化学吸附氧、铜离子还原温度和活性物种中氧气的脱附温度等进行分析。结果显示:Ce、Zr的引入不会对催化剂的骨架结构、结晶度和晶粒尺寸造成损伤;Ce、Zr的引入促进催化剂形成更多的氧空位和活性成分Cu—O—Cu2+,并增强催化剂的储氧和氧运输能力。当K+引入后,KCuZ5催化剂的脱硝活性明显降低、孔隙结构恶化以及K+与活性成分Cu—O—Cu2+结合迁移形成CuO;K+优先与Ce物种结合,进而有效保护ZSM-5的三维交叉孔道结构,减缓Cu2+迁移形成CuO以及促进活性成分Cu—O—Cu2+与Cu——Cu2+之间的氧化还原循环。

     

    Abstract: The most economical denitration method is the direct decomposition of NO into the most environmental friendly and cleanest N2 and O2 in the action of the Cu-ZSM-5 catalyst. There are a lot of alkali metals in the high temperature flue gas. However, the alkali metals can reduce the catalytic activity, shorten the service life of the catalyst, and cause an irreversible deactivation of the catalyst. The MZ5(M: Cu, Ce, Zr, CuCe, CuZr, CuCeZr) catalysts were prepared by the ion exchange method, and the K ions were loaded onto the MZ5 catalysts by the incipient wetness impregnation method. The results of the denitration experiments indicated that at the optimal reaction temperature of 550 ℃, the NO conversion rate of the CuCeZrZ5 catalyst increased from 53% to 58% compared with that of CuZ5; the NO conversion rate of the KCuCeZrZ5 catalyst increased from 39% to 52% compared with that of KCuZ5; and the NO conversion rate of the KCuCeZrZ5 catalyst increased from 53% to 52% compared with that of CuZ5. The ICP, SEM, XRD, BET, XPS, H2-TPR and O2-TPD were used to analyze thoroughly the element content, micro morphology, skeleton structure, pore law, copper species, chemical adsorption oxygen, copper ion reduction temperature and oxygen desorption temperature in active species. The characterization results showed that the introduction of Ce and Zr did not damage the framework structure, crystallinity and grain size of the catalyst, on the other hand, it promoted the formation of more oxygen vacancies and the active component Cu—O—Cu(2+ )in the catalyst, and enhanced the oxygen storage and transport capacity of the catalyst. When K+ was introduced, the denitrification activity of CuZ5 catalyst decreased obviously, the pore structure deteriorated, and CuO was formed by the migration of K(+ )with the active component Cu—O—Cu2+. K+ preferentially combined with Ce species, which effectively protects the unique three-dimensional cross-pore structure of ZSM-5, reduces the migration of Cu2+ to form CuO and promotes the redox cycle between the active component Cu—O—Cu2+ and Cu—□—Cu2+.

     

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