催化学报

催化学报 ›› 2016, Vol. 37 ›› Issue (12): 2069-2078.DOI: 10.1016/S1872-2067(16)62534-2

• 论文 • 上一篇    下一篇

Fe-Beta分子筛催化剂在选择催化还原氮氧化物反应中的活性:Fe含量的影响

夏岩, 詹望成, 郭耘, 郭杨龙, 卢冠忠   

  1. 华东理工大学结构可控先进功能材料及其制备教育部重点实验室和工业催化研究所, 上海 200237
  • 收稿日期:2016-08-29 修回日期:2016-09-30 出版日期:2016-12-27 发布日期:2016-12-27
  • 通讯作者: Wangcheng Zhan, Guanzhong Lu
  • 基金资助:

    国家重点基础研究发展计划（973计划，2013CB933201）；国家自然科学基金（21577034，21333003，91545103）；上海市自然科学基金（16ZR1407900）；中央高校基本科研业务费专项基金资助（WJ1514020）.

Fe-Beta zeolite for selective catalytic reduction of NOx with NH3: Influence of Fe content

Yan Xia, Wangcheng Zhan, Yun Guo, Yanglong Guo, Guanzhong Lu   

  1. Key Laboratory for Advanced Materials and Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China
  • Received:2016-08-29 Revised:2016-09-30 Online:2016-12-27 Published:2016-12-27
  • Contact: Wangcheng Zhan, Guanzhong Lu
  • Supported by:

    This work was supported by the National Key Basic Research Program of China (973 Program, 2013CB933201), the National Natural Science Foundation of China (21577034, 21333003, 91545103), Science and Technology Commission of Shanghai Municipality (16ZR1407900) and Fundamental Research Funds for the Central Universities (WJ1514020).

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摘要：

NOx是主要的大气污染物之一，对环境和人体健康具有极大的危害.其主要来源之一是柴油机尾气排放，V2O5-WO3/TiO2催化剂是现阶段大规模商用的SCR催化剂，但V2O5-WO3/TiO2催化剂相对较窄的温度窗口和V2O5的生物毒性使得迫切需要新型的环境友好的高效SCR催化剂，其中分子筛因其特殊的孔道结构和催化性能受到广泛的关注.用于SCR过程的分子筛主要包括ZSM-5，Beta，MOR，SAPO-34和SSZ-13等，通常采用Cu，Fe，Mn和Co等过渡金属对其进行改性，通过调变分子筛的表面酸性和氧化还原性能，提高催化剂的SCR活性.Beta分子筛具有三维12元环孔道结构，相对其它分子筛具有较好的水热稳定性，而且制备工艺成熟，价格低廉，因此该类分子筛催化剂在SCR过程中具有很好的应用前景.
我们采用离子交换法制备了系列Fe-Beta催化剂，发现将相同质量硝酸铁溶解在不同体积去离子水中，配制成不同浓度的硝酸铁溶液后与分子筛进行离子交换反应，制备得到的Fe-Beta催化剂中Fe的含量和NH3-SCR催化活性均存在显著差别.在此基础上，我们固定硝酸铁溶液浓度（0.02mol/L），通过增加溶液的体积，分别制备了Fe含量为（2.6，6.3和9）wt%的Fe-Beta分子筛.结果表明，Fe负载量为6.3 wt%时，Fe-Beta催化剂表现出最好的催化活性，NOx转化率大于80%的温度窗口为202-616℃.虽然三个催化剂在比表面积，孔径和Fe的价态上没有明显的差别，但Fe含量为6.3 wt%的催化剂在保持相对较高的Fe负载量的同时具有更多的孤立Fe3+物种，同时具有较好的NH3和NO吸附性能以及NO氧化能力，这些特性使得该催化剂相对于其它两个催化剂表现出更高的NH3-SCR催化活性.当Fe含量增加到9 wt%时，催化剂中FexOy纳米颗粒的含量大幅增加，使得NH3非选择性氧化能力加强，从而导致高温NH3-SCR反应活性大幅下降.

关键词: β分子筛, 选择催化还原, 铁含量, 铁物种, 离子交换

Abstract:

Fe doped Beta zeolite with different Fe contents were prepared by ion exchange by changing the volume or the concentration of a Fe salt solution. For a particular mass of Fe salt precursor, the concentration of the metal salt solution during ion exchange influenced the ion exchange capacity of Fe, and resulted in different activities of the Fe-Beta catalyst. Fe-Beta catalysts with the Fe contents of (2.6, 6.3 and 9) wt% were synthesized using different amounts of 0.02 mol/L Fe salt solution. These catalysts were studied by various characterization techniques and their NH3-SCR activities were evaluated. The Fe-Beta catalyst with the Fe content of 6.3 wt% exhibited the highest activity, with a temperature range of 202-616℃ where the NOx conversion was > 80%. The Fe content in Beta zeolite did not influence the structure of Beta zeolite and valence state of Fe. Compared with the Fe-Beta catalysts with low Fe content (2.6 wt%), Fe-Beta catalysts with 6.3 wt% Fe content possessed more isolated Fe3+ active sites which led to its higher NH3-SCR activity. A high capacity for NH3 and NO adsorption, and a high activity for NO oxidation also contributed to the high NH3-SCR activity of the Fe-Beta catalyst with 6.3 wt%. However, when the Fe content was further increased to 9.0 wt%, the amount of FexOy nanoparticles increased while the amount of isolated Fe3+ active sites was unchanged, which promoted NH3 oxidation and decreased the NH3-SCR activity at high temperature.

Key words: Beta zeolite, Selective catalytic reduction, Fe content, Fe species, Ion exchange