CIESC Journal ›› 2022, Vol. 73 ›› Issue (2): 672-680.DOI: 10.11949/0438-1157.20211230

• Catalysis, kinetics and reactors • Previous Articles     Next Articles

Study on the relationship of active centers and catalytic performance of Cu/SSZ-13 for NH3-SCR

Wei ZHOU1,2,3(),Fuye WANG3,Ning HE3,Haibin YU2,Xinbin MA1,Jiaxu LIU3()   

  1. 1.Institute of Chemical Engineering, Tianjin University, Tianjin 300350, China
    2.Center Tech Tianjin Chemical Research and Design Institute Co. , Ltd. , Tianjin 300131, China
    3.Institute of Chemical Engineering, Dalian University of Technology, Dalian 116023, Liaoning, China
  • Received:2021-08-25 Revised:2021-11-15 Online:2022-02-18 Published:2022-02-05
  • Contact: Jiaxu LIU

Cu/SSZ-13催化剂脱硝活性中心与催化性能构效关系的研究

周微1,2,3(),王福烨3,贺宁3,于海斌2,马新宾1,刘家旭3()   

  1. 1.天津大学化工学院,天津 300350
    2.中海油天津化工研究设计院有限公司,天津 300131
    3.大连理工大学化工学院,辽宁 大连 116023
  • 通讯作者: 刘家旭
  • 作者简介:周微(1985—),女,博士,362200922@163.com

Abstract:

Ammonia (NH3) selective catalytic reduction of nitrogen oxides (NH3-SCR) is currently the most promising diesel exhaust purification technology. The core of this technology is the development of catalysts with excellent catalytic performance. In recent years, Cu modified SSZ-13 zeolites with chabazite (CHA) topology as support have attracted extensive attention due to their excellent catalytic performance and hydrothermal stability. Therefore, in this study, a series of Cux/SSZ-13 catalysts with different Cu/Al ratios were prepared. The location and state of Cu ions on SSZ-13 zeolites with high catalytic activity was determined by insitu diffuse reflection infrared spectrum (DRIFT) using CO as probe molecule and H2-TPR. By means of CO adsorption experiments, it was found that the Cux/SSZ-13 catalysts prepared by the ion exchange method of Cu(NO3)2 aqueous solution had a variety of Cu+ active sites. For catalysts with low Cu ion exchange degree, Cu+ firstly located in the micro-channel of SSZ-13 zeolites. As Cu exchange degree increased, Cu+ would locate in the double-six-membered ring of SSZ-13 zeolites. H2-TPR characterization results show that there are also a large number of unstable Cu2+ located in the eight membered ring on Cux/SSZ-13 catalyst, which can be easily reduced to Cu+. For Cu/SSZ-13 catalyst aged by steam at 800℃ for 16 h, most of framework aluminum removed and Cu species agglomerated, both of which resulted in zeolites framework collapse. While, to a certain extent, the addition of Ce can improve the hydrothermal stability of Cu/SSZ-13 and protect the zeolites framework from collapse. The structure-activity relationship of the catalyst shows that the catalyst with a certain amount of stable Cu+ and a large amount of unstable Cu2+ has catalytic performance for NH3-SCR in a wide temperature range.

Key words: NH3-SCR reaction, Cu/SSZ-13 catalysts, Cu ion, reactivity

摘要:

NH3选择性催化还原NOx(NH3-SCR)是目前最有应用前景的柴油车尾气净化技术,该技术的核心是开发具备优异催化性能的催化剂。以具有菱沸石(chabazite,CHA)结构的小孔分子筛SSZ-13为载体制备的Cu/SSZ-13催化剂,因具有优异的催化性能和水热稳定性能而受到广泛关注。制备了系列Cux/SSZ-13催化剂,并通过CO原位漫反射红外光谱(DRIFT)和H2-TPR等方法能够确定具有高催化活性的铜离子在SSZ-13分子筛上的落位和存在状态。CO红外吸附实验发现,采用Cu(NO3)2水溶液离子交换法制备的Cu/SSZ-13催化剂上存在多种落位的Cu+活性中心。在较低的Cu+交换度条件下,Cu+优先落位于SSZ-13分子筛的八元环位置,随着交换度的提高,Cu+开始落位于SSZ-13分子筛双六元环的位置。H2-TPR结果表明Cux/SSZ-13催化剂上也存在大量落位在八元环位置不稳定的Cu2+,这些Cu2+很容易被还原为Cu+。Cux/SSZ-13催化剂经800℃水蒸气连续老化16 h,分子筛骨架崩塌程度随着Cu含量的增加而提高,骨架铝的脱除,导致Cu物种发生团聚,而第二金属Ce元素的引入能够在一定程度上提高Cu/SSZ-13的水热稳定性。催化剂构效关系研究表明,具有一定量稳定存在的Cu+,并且拥有大量不稳定存在Cu2+的催化剂具有较宽温度范围的脱硝性能。

关键词: NH3-SCR 反应, Cu/SSZ-13催化剂, 铜离子, 活性

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