催化学报 ›› 2019, Vol. 40 ›› Issue (1): 95-104.DOI: 10.1016/S1872-2067(18)63184-5

• 论文 • 上一篇    下一篇

Ce4+,Zr4+共掺杂提高V2O5-WO3/TiO2催化剂脱硝性能及抗K中毒能力

曹俊a,b, 姚小江b, 杨复沫c, 陈丽b, 傅敏a, 汤常金d, 董林d   

  1. a 重庆工商大学环境与资源学院, 重庆市催化与环境新材料重点实验室, 重庆 400067;
    b 中国科学院重庆绿色智能技术研究院大气环境研究中心, 重庆 400714;
    c 四川大学建筑与环境学院, 烟气脱硫国家工程研究中心, 四川成都 610065;
    d 南京大学现代分析中心, 江苏省机动车尾气控制重点实验室, 江苏南京 210093
  • 收稿日期:2018-08-22 修回日期:2018-09-28 出版日期:2019-01-18 发布日期:2018-11-09
  • 通讯作者: 姚小江, 傅敏
  • 基金资助:

    国家自然科学基金(21876168,21507130);重庆市重点产业共性关键技术创新重点项目(cstc2016zdcy-ztzx0020-01);重庆市科学技术委员会项目(cstc2016jcyjA0070,cstckjcxljrc13);重庆工商大学催化与功能有机分子重庆市重点实验室开放课题(1456029);重庆工商大学研究生创新项目(yjscxx201803-028-22).

Improving the denitration performance and K-poisoning resistance of the V2O5-WO3/TiO2 catalyst by Ce4+ and Zr4+ co-doping

Jun Caoa,b, Xiaojiang Yaob, Fumo Yangc, Li Chenb, Min Fua, Changjin Tangd, Lin Dongd   

  1. a Chongqing Key Laboratory of Catalysis and New Environmental Materials, College of Environment and Resources, Chongqing Technology and Business University, Chongqing 400067, China;
    b Research Center for Atmospheric Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China;
    c National Engineering Research Center for Flue Gas Desulfurization, School of Architecture and Environment, Sichuan University, Chengdu 610065, Sichuan, China;
    d Jiangsu Key Laboratory of Vehicle Emissions Control, Center of Modern Analysis, Nanjing University, Nanjing 210093, Jiangsu, China
  • Received:2018-08-22 Revised:2018-09-28 Online:2019-01-18 Published:2018-11-09
  • Contact: 10.1016/S1872-2067(18)63184-5
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21876168, 21507130), the Key Projects for Common Key Technology Innovation in Key Industries in Chongqing (cstc2016zdcy-ztzx0020-01), the Chongqing Science & Technology Commission (cstc2016jcyjA0070, cstckjcxljrc13), the Open Project Program of Chongqing Key Laboratory of Catalysis and Functional Organic Molecules from Chongqing Technology and Business University (1456029), and the Graduate Innovation Project of Chongqing Technology and Business University (yjscxx201803-028-22).

摘要:

近年来,NOx的排放造成了严重的环境污染.氨选择性催化还原技术(NH3-SCR)是目前消除NOx最有效的手段之一.V2O5-WO3/TiO2催化剂在300-400℃范围内表现出优异的脱硝性能,因此被广泛用于NH3-SCR反应.然而该催化剂抗碱(土)金属中毒性能较差,且碱(土)金属碱性越强对催化剂的毒害越大(即K > Na > Ca > Mg).已有研究显示,当K2O质量分数达1%时,催化剂将完全失活,所以对传统的V2O5-WO3/TiO2催化剂进行改性以提高其抗K中毒性能具有十分重要的意义.
最近,CeO2由于具有优异的氧化还原性能和储/释氧能力,在NH3-SCR反应得到了广泛的关注.研究显示,CeO2的改性可提高钒基催化剂脱硝活性及抗碱金属中毒性能,这主要是由于CeO2的掺杂可以有效提高催化剂表面酸性及氧化还原能力.ZrO2是一种酸碱两性氧化物,常被用作载体或者助剂.研究显示,ZrO2的引入可以提高催化剂热稳定性,增大比表面积以及提高氧迁移能力.基于此,我们制备了一系列的V2O5-WO3/TiO2-ZrO2,V2O5-WO3/TiO2-CeO2以及V2O5-WO3/TiO2-CeO2-ZrO2催化剂,以期提高V2O5-WO3/TiO2催化剂脱硝性能及抗K中毒能力.
研究发现,Ce4+,Zr4+共掺杂可以有效提高V2O5-WO3/TiO2催化活性,拓宽反应温度窗口,增强抗K中毒能力.进一步借助X射线衍射、比表面积测定、氨气-程序升温脱附、氢气-程序升温还原和X射线光电子能谱等表征对催化剂进行全面分析.结果显示,Ce4+,Zr4+共掺杂对V2O5-WO3/TiO2催化剂物理化学性质的影响与其脱硝性能及抗K中毒能力有着密不可分的关系.首先,Ce4+,Zr4+可以掺杂进入TiO2晶格,抑制TiO2晶粒的生长,从而导致比表面积以及总孔体积的增加;比表面积的增加有利于活性物种的分散,而总孔体积的增加有利于反应物分子与催化剂充分接触.其次,Ce4+,Zr4+共掺杂可以提高催化剂表面酸性和氧化还原性能,表面酸性的增加有利于催化剂吸附与活化反应物种NH3,氧化还原性能的提高有利于NO氧化为NO2,进而通过"快速NH3-SCR"反应提高催化剂活性;同时,Ce4+,Zr4+共掺杂还可以有效降低K中毒对表面酸性和氧化还原性能的影响,这主要是由于Ce4+可以与K原子结合形成Ce-O-K物种,而Zr4+的引入可以增加Ce4+的热稳定性,使得更多的Ce4+与K结合,避免了K与活性钒物种结合形成V-O-K物种,使得活性V5+得到了有效的保护.原位红外实验揭示了V2O5-WO3/TiO2-CeO2-ZrO2催化反应遵循L-H机理,且K中毒并未改变其反应机理.最后,该催化剂在H2O和SO2存在的条件下仍具有最佳的脱硝性能,因而有望用于实际高K含量的燃煤烟气脱硝.

关键词: V2O5-WO3/TiO2-CeO2-ZrO2催化剂, 共掺杂, 钾中毒, 氨-选择性催化还原, 反应机理

Abstract:

A series of V2O5-WO3/TiO2-ZrO2, V2O5-WO3/TiO2-CeO2, and V2O5-WO3/TiO2-CeO2-ZrO2 catalysts were synthesized to improve the selective catalytic reduction (SCR) performance and the K-poisoning resistance of a V2O5-WO3/TiO2 catalyst. The physicochemical properties were investigated by using XRD, BET, NH3-TPD, H2-TPR, and XPS, and the catalytic performance and K-poisoning resistance were evaluated via a NH3-SCR model reaction. Ce4+ and Zr4+ co-doping were found to enhance the conversion of NOx, and exhibit the best K-poisoning resistance owing to the largest BET-specific surface area, pore volume, and total acid site concentration, as well as the minimal effects on the surface acidity and redox ability from K poisoning. The V2O5-WO3/TiO2-CeO2-ZrO2 catalyst also presents outstanding H2O + SO2 tolerance. Finally, the in situ DRIFTS reveals that the NH3-SCR reaction over the V2O5-WO3/TiO2-CeO2-ZrO2 catalyst follows an L-H mechanism, and that K poisoning does not change the reaction mechanism.

Key words: V2O5-WO3/TiO2-CeO2-ZrO2 catalyst, Co-doping, K-poisoning, NH3-SCR, Reaction mechanism