催化学报

催化学报 ›› 2017, Vol. 38 ›› Issue (1): 146-159.DOI: 10.1016/S1872-2067(16)62572-X

• 论文 • 上一篇    下一篇

制备方法对MnOx-CeO2催化剂理化性质及低温NH3-SCR脱硝性能的影响

姚小江a, 马凯莉b, 邹伟欣b, 何圣贵c, 安继斌d, 杨复沫a,e, 董林b   

  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 中国科学院化学研究所, 北京分子科学国家实验室, 北京 100190;
    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;
    e 中国科学院城市环境研究所, 中国科学院区域大气环境研究卓越创新中心, 福建厦门 361021
  • 收稿日期:2016-09-01 修回日期:2016-09-28 出版日期:2017-01-18 发布日期:2017-01-18
  • 通讯作者: Xiaojiang Yao,Tel:+86-23-65935909;Fax:+86-23-65935924;E-mail:yaoxj@cigit.ac.cn;Fumo Yang,Tel:+86-23-65935909;Fax:+86-23-65935924;E-mail:fmyang@cigit.ac.cn;Lin Dong,Tel:+86-25-83592290;Fax:+86-25-83317761;E-mail:donglin@nju.edu.cn
  • 基金资助:

    国家自然科学基金（批准号21507130）；北京分子科学国家实验室开放课题（批准号20140142）；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（批准号CEK1405）；江苏省机动车尾气污染控制重点实验室开放课题（批准号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（批准号1456029）；重庆市科学技术委员会项目（批准号cstc2016jcyjA0070，cstc2014pt-gc20002，cstckjcxljrc13）.

Influence of preparation methods on the physicochemical properties and catalytic performance of MnOx-CeO2 catalysts for NH3-SCR at low temperature

Xiaojiang Yaoa, Kaili Mab, Weixin Zoub, Shenggui Hec, Jibin And, Fumo Yanga,e, Lin Dongb   

  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 Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China;
    d Chongqing Key Laboratory of Environmental Materials and Remediation Technology, Chongqing University of Arts and Sciences, Chongqing 402160, China;
    e Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, Fujian, China
  • Received:2016-09-01 Revised:2016-09-28 Online:2017-01-18 Published:2017-01-18
  • Contact: Xiaojiang Yao,Tel:+86-23-65935909;Fax:+86-23-65935924;E-mail:yaoxj@cigit.ac.cn;Fumo Yang,Tel:+86-23-65935909;Fax:+86-23-65935924;E-mail:fmyang@cigit.ac.cn;Lin Dong,Tel:+86-25-83592290;Fax:+86-25-83317761;E-mail:donglin@nju.edu.cn
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (No. 21507130); the Open Project Program of Beijing National Labor-atory for Molecular Sciences (No. 20140142); the Open Project Program of Chongqing Key Laboratory of Environmental Materials and Remediation Technology from Chongqing University of Arts and Sciences (No. CEK1405); the Open Project Program of Jiangsu Key Laboratory of Vehicle Emissions Control (No. 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 (Nos. cstc2016jcyjA0070, cstc2014pt-gc20002, cstckjcxljrc13).

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摘要：

随着人们环保意识的增强，氮氧化物（NOx）的危害引起广泛关注.NOx作为首要的大气污染物之一，主要来源于以燃煤电厂为代表的固定源和以机动车为代表的移动源.它不仅能够导致酸雨和光化学烟雾，而且还是PM2.5的重要前驱体，严重危害人类健康和植物生长.因此，NOx的治理迫在眉睫.研究表明，氨选择性催化还原（NH3-SCR）技术是控制固定源NOx排放最经济有效的方法.
商业化V2O5-WO3/TiO2和V2O5-MoO3/TiO2脱硝催化剂的最佳工作温度窗口为300-400℃.因此，NH3-SCR脱硝设施通常安装在除尘器和脱硫装置之前以满足最佳工作温度需要.然而，在这种情况下，脱硝催化剂容易因烟气中的飞灰和含硫化合物堵塞、中毒而失活.此外，对于老电厂增加脱硝设施的改造工程，在除尘器和脱硫装置之前没有足够的空间用于安装脱硝设施.因此，开发环境友好型低温NH3-SCR脱硝催化剂显得尤为重要，因为它可以直接安装在除尘器和脱硫装置之后，从而有效减缓脱硝催化剂失活，有利于改造工程的施工.
研究表明，锰基催化剂由于其优异的氧化还原性能和氧迁移能力有利于氧化NO为NO2，促进反应沿着“快速NH3-SCR”途径进行，从而表现出优异的低温脱硝性能.然而，其N2选择性、抗水性能和工作温度窗口还有待改善.因此，开发既具有高催化活性又具有宽工作温度窗口、优异抗水性能以及理想N2选择性的低温脱硝催化剂仍是一个富有挑战性的课题.
二氧化铈（CeO2）由于具有优异的氧化还原性能、良好的储/释氧能力、丰富的氧空位以及Ce4+/Ce3+的轻易切换而被广泛用于NH3-SCR反应.因此，将锰氧化物（MnOx）与CeO2相结合而制备的MnOx-CeO2催化剂可能会表现出优异的低温脱硝性能.而催化剂的理化性质和催化性能还强烈地依赖于其制备方法.因此，本文采用不同方法（机械混合法、浸渍法、水热法、共沉淀法以及溶胶-凝胶法）制备了一系列MnOx-CeO2催化剂用于低温NH3-SCR反应，并运用X射线衍射（XRD）、拉曼光谱（Raman）、氮气物理吸附、氢气程序升温还原（H2-TPR）、氨气程序升温脱附（NH3-TPD）、X射线光电子能谱（XPS）以及原位漫反射红外光谱（in situ DRIFTS）等表征技术对催化剂进行了系统分析.重点考察了制备方法对MnOx-CeO2催化剂理化性质和催化性能的影响.
结果表明，低温脱硝性能有如下顺序：水热法 > 溶胶-凝胶法 > 共沉淀法 > 浸渍法 > 机械混合法.这与催化剂表面Ce3+和Mn4+含量、氧空位和表面吸附氧物种浓度以及酸量和酸强度顺序一致.这些性质都与MnOx和CeO2之间的电子相互作用（即Mn3++Ce4+↔Mn4++Ce3+）密切相关.特别是水热法制备的MnOx-CeO2催化剂（MnCe-HTM）由于Mnn+掺入到CeO2晶格形成铈基固溶体（含Mn-O-Ce结构）以及水热过程中的高温高压环境加强了MnOx和CeO2之间的电子相互作用，从而表现出优异的理化性质、最佳的低温脱硝性能以及理想的抗水性能.

关键词: MnOx-CeO2催化剂, 制备方法, 氮氧化物, 低温氨选择性催化还原, 电子相互作用, 表面酸性

Abstract:

This work examines the influence of preparation methods on the physicochemical properties and catalytic performance of MnOx-CeO2 catalysts for selective catalytic reduction of NO by NH3 (NH3-SCR) at low temperature. Five different methods, namely, mechanical mixing, impregnation, hydrothermal treatment, co-precipitation, and a sol-gel technique, were used to synthesize MnOx-CeO2 catalysts. The catalysts were characterized in detail, and an NH3-SCR model reaction was chosen to evaluate the catalytic performance. The results showed that the preparation methods affected the catalytic performance in the order:hydrothermal treatment > sol-gel > co-precipitation > impregnation > mechanical mixing. This order correlated with the surface Ce3+ and Mn4+ content, oxygen vacancies and surface adsorbed oxygen species concentration, and the amount of acidic sites and acidic strength. This trend is related to redox interactions between MnOx and CeO2. The catalyst formed by a hydrothermal treatment exhibited excellent physicochemical properties, optimal cata-lytic performance, and good H2O resistance in NH3-SCR reaction. This was attributed to incorpora-tion of Mnn+ into the CeO2 lattice to form a uniform ceria-based solid solution (containing Mn-O-Ce structures). Strengthening of the electronic interactions between MnOx and CeO2, driven by the high-temperature and high-pressure conditions during the hydrothermal treatment also improved the catalyst characteristics. Thus, the hydrothermal treatment method is an efficient and environ-ment-friendly route to synthesizing low-temperature denitrification (deNOx) catalysts.

Key words: MnOx-CeO2 catalyst, Preparation method, Nitrogen oxides, Low-temperature NH3-SCR, Electron interaction, Surface acidity