催化学报 ›› 2016, Vol. 37 ›› Issue (8): 1369-1380.DOI: 10.1016/S1872-2067(15)61098-1

• 论文 • 上一篇    下一篇

高效CeO2-MnOx-Al2O3催化剂的制备、表征及催化消除NO性能

姚小江a, 李露露b,c, 邹伟欣b,c, 虞硕涵b,c, 安继斌d, 李红丽a, 杨复沫a, 董林b,c   

  1. a. 中国科学院重庆绿色智能技术研究院, 中国科学院水库水环境重点实验室, 重庆 400714;
    b. 南京大学化学化工学院, 介观化学教育部重点实验室, 江苏 南京 210093;
    c. 南京大学现代分析中心, 江苏省机动车尾气污染控制重点实验室, 江苏 南京 210093;
    d. 重庆文理学院, 环境材料与修复技术重庆市重点实验室, 重庆 402160
  • 收稿日期:2016-02-16 修回日期:2016-03-20 出版日期:2016-07-29 发布日期:2016-08-01
  • 通讯作者: Xiaojiang Yao, Fumo Yang, Lin Dong
  • 基金资助:

    国家自然科学基金(21507130);重庆文理学院环境材料与修复技术重庆市重点实验室开放课题(CEK1405);北京分子科学国家实验室开放课题(20140142);江苏省机动车尾气污染控制重点实验室开放课题(OVEC001);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);重庆市科学技术委员会项目(cstc2014pt-gc20002).

Preparation, characterization, and catalytic performance of high efficient CeO2-MnOx-Al2O3 catalysts for NO elimination

Xiaojiang Yaoa, Lulu Lib,c, Weixin Zoub,c, Shuohan Yub,c, Jibin And, Hongli Lia, Fumo Yanga, Lin Dongb,c   

  1. a. Key Laboratory of Reservoir Aquatic Environment of CAS, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China;
    b. Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, Jiangsu, China;
    c. Jiangsu Key Laboratory of Vehicle Emissions Control, Center of Modern Analysis, Nanjing University, Nanjing 210093, Jiangsu, China;
    d. Chongqing Key Laboratory of Environmental Materials and Remediation Technology, Chongqing University of Arts and Sciences, Chongqing 402160, China
  • Received:2016-02-16 Revised:2016-03-20 Online:2016-07-29 Published:2016-08-01
  • Contact: Xiaojiang Yao, Fumo Yang, Lin Dong
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21507130), the Open Project Program of Chongqing Key Laboratory of Environmental Materials and Remediation Technology from Chongqing University of Arts and Sciences (CEK1405), the Open Project Program of Beijing National Laboratory for Molecular Sciences (20140142), the Open Project Program of Jiangsu Key Laboratory of Vehicle Emissions Control (OVEC001), the Open Project Program of Chongqing Key Laboratory of Catalysis and Functional Organic Molecules from Chongqing Technology and Business University (1456029), and the Chongqing Science & Technology Commission (cstc2014pt-gc20002).

摘要:

机动车在给人类生活带来便利的同时,也造成了严重的大气污染.其尾气净化成为人们关注的焦点.一氧化氮(NO)、一氧化碳(CO)和碳氢化合物(HCs)是机动车尾气中的三大典型污染物,主要通过三效催化(TWC)技术进行脱除.TWC技术涉及几个重要的催化反应,其中CO催化还原NO由于能够同时消除CO和NO两种污染物而引起研究者的极大关注.研究表明,负载型贵金属催化剂在该反应中显示出优异的催化性能,但存在资源匮乏、价格昂贵以及热稳定性欠佳等不足.因此,低价、高效的过渡金属氧化物催化剂成为近年研究重点.稀土金属氧化物CeO2由于具有良好的氧化还原性能、较高的储释氧容量以及丰富的表面氧空位而被广泛用于CO催化还原NO反应.研究表明,对CeO2进行离子掺杂可进一步增大其比表面积,改善其氧化还原性能和储释氧容量.并且,我们在先前的研究中还发现,将具有多种可变价态的钛离子或锡离子掺入CeO2晶格由于掺杂离子能与Ce4+/Ce3+发生电子转移而更有利于改善CeO2的理化性质.此外,锰氧化物(MnOx)在氧化还原气氛中容易实现不同价态之间的切换,从而在一些重要的氧化还原反应中表现出优异的催化性能.近年来,有研究者将CeO2与MnOx相结合制备了CeO2-MnOx催化剂用于NO消除、碳烟燃烧和挥发性有机物(VOCs)氧化等反应,并取得一些有意义的结果.然而,对于实际应用来说,CeO2-MnOx催化剂存在比表面积偏小等不足.众所周知,γ-Al2O3是一种常用的具有高比表面积和高热稳定性的催化剂载体材料,可有效增大催化剂比表面积.我们前期研究结果表明,通过共沉淀法将Al3+掺入铈基复合氧化物的晶格相比于以γ-Al2O3为载体更有利于改善铈基复合氧化物的理化性质和催化性能.因此,我们通过简单的氨水反滴加共沉淀法制备了一系列CeO2-MnOx-Al2O3 (Ce:Mn:Al摩尔比= 6:4:xx = 0.25,0.5,1,2)复合氧化物催化剂用于CO催化还原NO反应.并运用X射线衍射、拉曼光谱、氮气物理吸附、氢气程序升温还原、X射线光电子能谱以及原位漫反射红外光谱等表征技术对上述催化剂进行了系统分析.重点考察了Al3+掺杂量对CeO2-MnOx-Al2O3复合氧化物催化剂理化性质和催化性能的影响.结果表明,在CeO2-MnOx复合氧化物中掺入少量Al3+会导致其晶粒尺寸减小,从而增大其比表面积和孔体积,并增加Ce3+和Mn4+的含量.比表面积和孔体积增大有助于催化剂与反应物分子之间充分接触; Ce3+和Mn4+含量增加能分别促进CO物种吸附以及吸附态NO物种脱附、转化和解离.这些变化有利于提高CeO2-MnOx复合氧化物在CO催化还原NO反应中的催化性能.最后,基于催化剂的理化性质表征及其催化性能评价,我们尝试提出了一个可能的催化反应机理,以进一步理解CeO2-MnOx-Al2O3复合氧化物催化剂在CO催化还原NO反应中的优异性能.

关键词: 铈基复合氧化物, 掺杂, 电子相互作用, 吸附性质, NO消除

Abstract:

A series of CeO2-MnOx-Al2O3 mixed oxide catalysts (Ce:Mn:Al mole ratio = 6:4:x, x = 0.25, 0.5, 1, 2) were prepared by a simple one-step inverse co-precipitation method to investigate the influence of the incorporation of Al3+ into CeO2-MnOx mixed oxides. CeO2-MnOx, CeO2-Al2O3, and MnOx-Al2O3 mixed oxides, and CeO2 were prepared by the same method for comparison. The samples were characterized by XRD, Raman, N2 physisorption, H2-TPR, XPS, and in situ DRIFTS. The catalytic reduction of NO by CO was chosen as a model reaction to evaluate the catalytic performance. The incorporation of a small amount of Al3+ into CeO2-MnOx mixed oxides resulted in a decrease of crystallite size, with the increase of the BET specific surface area and pore volume, as well as the increase of Ce3+ and Mn4+. The former benefits good contact between catalyst and reactants, and the latter promotes the adsorption of CO and the desorption, conversion and dissociation of adsorbed NO. All these enhanced the catalytic performance for the NO+CO model reaction. A reaction mechanism was proposed to explain the excellent catalytic performance of CeO2-MnOx-Al2O3 catalysts for NO reduction by CO.

Key words: Ceria-based mixed oxide, Incorporation, Electron interaction, Adsorption property, NO elimination