催化学报 ›› 2017, Vol. 38 ›› Issue (8): 1423-1430.

• 论文 • 上一篇    

负载型铈基催化剂在NH3-SCR反应中的载体效应

姚小江a,b,c, 陈丽c,d, 孔婷婷a,c, 丁世敏a, 罗琼c, 杨复沫a,b,c,d   

  1. a 长江师范学院武陵山片区绿色发展协同创新中心, 重庆 408100;
    b 中国科学院城市环境研究所区域大气环境研究卓越创新中心, 福建厦门 361021;
    c 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;
    d 重庆大学城市建设与环境工程学院, 重庆 400045
  • 收稿日期:2017-05-15 修回日期:2017-06-07 出版日期:2017-08-18 发布日期:2017-08-04
  • 通讯作者: 姚小江, 杨复沫
  • 基金资助:

    国家自然科学基金(21507130);重庆市科学技术委员会项目(cstc2016jcyjA0070,cstc2014pt-gc20002,cstc2014yykfC20003,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).

Support effect of the supported ceria-based catalysts during NH3-SCR reaction

Xiaojiang Yaoa,b,c, Li Chenc,d, Tingting Konga,c, Shimin Dinga, Qiong Luoc, Fumo Yanga,b,c,d   

  1. a Collaborative Innovation Center for Green Development in Wuling Mountain Areas, Yangtze Normal University, Chongqing 408100, China;
    b Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, Fujian, China;
    c Research Center for Atmospheric Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China;
    d School of Urban Construction and Environmental Engineering, Chongqing University, Chongqing 400045, China
  • Received:2017-05-15 Revised:2017-06-07 Online:2017-08-18 Published:2017-08-04
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21507130), the Chongqing Science and Technology Commission (cstc2016jcyjA0070, cstc2014pt-gc20002, cstc2014yykfC20003, cstckjcxljrc13), and the Open Project Program of Chongqing Key Laboratory of Catalysis and Functional Organic Molecules from Chongqing Technology and Business University (1456029).

摘要:

近年来,氨-选择催化还原(NH3-SCR)技术被公认为是控制燃煤烟气和柴油车尾气氮氧化物(NOx)排放的最有效手段之一.V2O5-WO3/TiO2和V2O5-MoO3/TiO2催化剂在300-400℃范围内表现出优异的脱硝性能和抗H2O和SO2中毒性能,因而被广泛用于NH3-SCR过程.然而,钒基催化剂存在一些缺点,如氧化SO2到SO3的活性较高、高温下将部分NH3非选择性地氧化成N2O、V2O5具有生物毒性等.因此,非钒基脱硝催化剂的研制引起人们越来越多的关注.二氧化铈(CeO2)因具有氧化还原性能优异、储/释氧能力强和Ce3+/Ce4+转换容易等优点而广泛用于NH3-SCR反应.然而,单纯CeO2的脱硝性能并不理想.研究表明,将CeO2制备成铈基复合金属氧化物催化剂和负载型铈基催化剂可显著提高其在NH3-SCR反应中的催化性能.尤其是负载型铈基催化剂由于催化性能优异、比表面积大、热稳定性高及活性组分用量少而成为研究热点.众所周知,对于负载型金属氧化物催化剂,载体并不只是惰性材料,它会显著影响表面负载组分的物理化学性质和催化性能.因此,关于载体与组分间相互作用的研究常见诸报道.但是,对于负载型铈基催化剂,具有不同晶相结构的载体对其理化性质和NH3-SCR催化性能的影响规律尚不明晰.此外,SiO2γ-Al2O3,ZrO2和TiO2是工业上常用的四种催化剂载体,它们具有不同的晶相结构和应用场合,究竟哪一个最适合作为负载型铈基催化剂的载体用于NH3-SCR反应尚无定论.因此,为了阐明负载型铈基催化剂在NH3-SCR反应中的载体效应,筛选出最佳的催化剂载体,我们首先采用溶胶-凝胶法和沉淀法合成了SiO2γ-Al2O3,ZrO2和TiO2四个载体,再通过浸渍法制备了一系列负载型铈基催化剂(CeO2/SiO2,CeO2/γ-Al2O3,CeO2/ZrO2和CeO2/TiO2)用于NH3-SCR反应.并借助于X射线衍射(XRD)、拉曼光谱(Raman)、比表面积测定(BET)、X射线光电子能谱(XPS)、氢气-程序升温还原(H2-TPR)以及氨气-程序升温脱附(NH3-TPD)等表征手段对上述载体和催化剂进行了较为全面的分析.研究结果表明,这些负载型铈基催化剂的理化性质和脱硝性能强烈地依赖于催化剂载体.首先,CeO2/γ-Al2O3催化剂的表面Ce3+含量明显大于CeO2/SiO2,CeO2/ZrO2和CeO2/TiO2催化剂,有利于氧空位的产生以促进NO分子的解离,进而导致优异的NH3-SCR反应性能.其次,CeO2/γ-Al2O3催化剂具有最佳的还原性能,有利于NO氧化为NO2,进而通过“快速NH3-SCR”途径提升其催化性能.再者,CeO2/γ-Al2O3催化剂表面酸性位最多,能够促进反应物NH3分子的吸附与活化,从而提高脱硝性能.最后,CeO2/γ-Al2O3催化剂在H2O和SO2存在的条件下同样表现出最佳的催化性能,表明其有望用于实际燃煤烟气脱硝.

关键词: 载体效应, 负载型铈基催化剂, 还原性能, 表面酸性, 氨-选择催化还原

Abstract:

To investigate how the physicochemical properties and NH3-selective catalytic reduction (NH3-SCR) performance of supported ceria-based catalysts are influenced as a function of support type, a series of CeO2/SiO2, CeO2/γ-Al2O3, CeO2/ZrO2, and CeO2/TiO2 catalysts were prepared. The physicochemical properties were probed by means of X-ray diffraction, Raman spectroscopy, Brunauer-Emmett-Teller surface area measurements, X-ray photoelectron spectroscopy, H2-temperature programmed reduction, and NH3-temperature programmed desorption. Furthermore, the supported ceria-based catalysts' catalytic performance and H2O + SO2 tolerance were evaluated by the NH3-SCR model reaction. The results indicate that out of the supported ceria-based catalysts studied, the CeO2/γ-Al2O3 catalyst exhibits the highest catalytic activity as a result of having a high relative Ce3+/Ce4+ ratio, optimum reduction behavior, and the largest total acid site concentration. Finally, the CeO2/γ-Al2O3 catalyst also presents excellent H2O + SO2 tolerance during the NH3-SCR process.

Key words: Support effect, Supported ceria-based catalyst, Reduction behavior, Surface acidity, Ammonia-selective catalytic reduction