催化学报

催化学报 ›› 2016, Vol. 37 ›› Issue (8): 1354-1361.DOI: 10.1016/S1872-2067(15)61102-0

• 论文 • 上一篇    下一篇

Zr的添加对CeTiOxNH3-SCR催化剂抗碱金属中毒能力的提升

徐宝强a, 徐海迪b,c, 林涛a, 曹毅a, 兰丽a, 李元山d, 冯锡d, 龚茂初a, 陈耀强a,c   

  1. a. 四川大学化学学院绿色化学与技术教育部重点实验室, 四川 成都 610064;
    b. 四川大学新能源与低碳技术研究院, 四川 成都 610064;
    c. 四川省环境保护环境催化材料工程技术中心, 四川 成都 610064;
    d. 四川大学化学工程学院, 四川 成都 610064
  • 收稿日期:2016-02-27 修回日期:2016-04-02 出版日期:2016-07-29 发布日期:2016-08-01
  • 通讯作者: Haidi Xu, Yaoqiang Chen
  • 基金资助:

    四川省科技支撑计划（2012FZ0008）；国家自然科学基金（21173153）；国家高技术研究发展计划（863计划，2013AA065304）；四川大学青年教师科研启动基金（2015SCU11056）.

Promotional effects of Zr on K+-poisoning resistance of CeTiOx catalyst for selective catalytic reductionof NOx with NH3

Baoqiang Xua, Haidi Xub,c, Tao Lina, Yi Caoa, Li Lana, Yuanshan Lid, Xi Fengd, Maochu Gonga, Yaoqiang Chena,c   

  1. a. Key Laboratory of Green Chemistry & Technology of the Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, Sichuan, China;
    b. Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu 610064, Sichuan, China;
    c. Sichuan Provincial Environmental Protection Environmental Catalytic Materials Engineering Technology Center, Chengdu 610064, Sichuan, China;
    d. College of Chemical Engineering, Sichuan University, Chengdu 610064, Sichuan, China
  • Received:2016-02-27 Revised:2016-04-02 Online:2016-07-29 Published:2016-08-01
  • Contact: Haidi Xu, Yaoqiang Chen
  • Supported by:

    This work was supported by the Major Research Program of Sichuan Province Science and Technology Department (2012FZ0008), the National Natural Science Foundation of China (21173153), the National High Technology Research and Development Program of China (863 Program, 2013AA065304), and the Sichuan University Research Foundation for Young Teachers (2015SCU11056).

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摘要：

CeTiOx具有高的NH3选择性催化还原（NH3-SCR）活性和N2选择性，被认为是具有应用前景的催化剂.但是，CeTiOx不抗碱金属中毒，在含有大量K离子的生物质柴油的燃烧装置中中毒尤为严重，因而限制了CeTiOx催化剂在生物质燃料装置上的进一步应用.本文通过在CeTiOx催化剂中掺杂Zr元素来提升其抗K+中毒的能力.采用共沉淀法制备了CeTiOx（CT）和CeZrTiOx（ZCT）两种NH3-SCR催化剂.将不同含量的硝酸钾（K+/Ce=0.1，0.2）负载在催化剂表面，焙烧处理后得到K+中毒的催化剂（K0.1-CT，K0.2-CT，K0.1-ZCT和K0.2-ZCT）.通过测定各催化剂的催化活性来研究Zr的添加对CT催化剂抗K+中毒能力的影响.NH3-SCR活性数据表明，CT和ZCT催化剂都达到了接近100%的NOx转化率，且两种新鲜催化剂的催化性能基本无差别.浸渍不同含量的K+之后，ZCT催化剂明显优于CT催化剂：K0.1-CT和K0.1-ZCT上的NOx转化率分别为90%和62%；而K0.2-CT和K0.2-ZCT上分别为48%和13%.可见，随K+添加，ZCT催化剂活性降低更缓慢，表明Zr的添加提高了CT催化剂抗K+中毒能力.BET数据显示，在新鲜催化剂中，Zr的添加增加了催化剂比表面积和孔体积；K+中毒之后，ZCT仍然表现出比CT更好的织构性能.X射线衍射和拉曼光谱结果显示，随着K+负载量的增加，锐钛矿TiO2的衍射峰逐渐变得尖锐，说明无定形TiO2逐渐结晶并不断长大，从而导致催化剂比表面积下降.与CT相比，随着K+负载量增加，催化剂晶型并没有明显变化.这说明Zr的添加可以抑制锐钛矿TiO2的结晶及长大.由此可见Zr的添加可抑制因K+中毒而引起的催化剂结构变化，所以仍能保持较高的NOx转化率.透射电镜（TEM）结果表明，随着K+负载量逐渐增加，催化剂的晶粒尺寸逐渐变大：CT，K0.1-CT和K0.2-CT的平均晶粒尺寸分别为7，13和15nm，而ZCT催化剂晶粒尺寸增大并不明显，分别为5，8和10nm.很明显，Zr的添加抑制了催化剂晶粒长大，从而提高了其结构稳定性能.综上可见，由负载KNO3而引起的“熔盐效应”得到了有效抑制.X射线光电子能谱结果表明，随着K+负载量增加，CeZrTiOx催化剂的Ce3+/Ce4+值下降得比CeTiOx更缓慢，说明加入Zr之后，催化剂具有更多的晶格缺陷和氧空缺，因而有利于NH3-SCR活性的提高.另外，催化剂酸性也是影响NH3-SCR活性的关键因素.NH3程序升温脱附结果显示，Zr的添加可以使CeTiOx催化剂在K+中毒之后仍保持较高的酸性，即Zr的添加抑制了K+对催化剂表面酸性的巨大破坏作用.综上可知，Zr的添加提升了CeTiOx催化剂抗K+中毒能力.

关键词: 铈钛复合氧化物, 氧化锆, 抗钾中毒, 选择性催化还原, 氮氧化物

Abstract:

CeTiOx and CeZrTiOx catalysts were prepared by a coprecipitation method and used for selective catalytic reduction of NOx by NH3 (NH3-SCR). Various amounts of KNO3 were impregnated on the catalyst surface to investigate the effects of Zr addition on the K+-poisoning resistance of the CeTiOx catalyst. The NH3-SCR performance of the catalysts showed that the NOx removal activity of the Zr-modified catalyst after poisoning was better than that of the CeTiOx catalyst. Brunauer-Emmett-Teller data indicated that the Zr-containing catalyst had a larger specific surface area and pore volume both before and after K+ poisoning. X-ray diffraction, Raman spectroscopy, and transmission electron microscopy showed that Zr doping inhibited anatase TiO2 crystal grain growth, i.e., the molten salt flux effect caused by the loaded KNO3 was inhibited. The Ce 3d X-ray photoelectron spectra showed that the Ce3+/Ce4+ ratio of CeZrTiOx decreased more slowly than that of CeTiOx with increasing K+ loading, indicating that Zr addition preserved more crystal defects and oxygen vacancies; this improved the catalytic performance. The acidity was a key factor in the NH3-SCR performance; the temperature-programmed desorption of NH3 results showed that Zr doping inhibited the decrease in the surface acidity. The results suggest that Zr improved the K+-poisoning resistance of the CeTiOx catalyst.

Key words: Cerium-titanium mixed oxide, Zirconium, Potassium-poisoning resistance, Selective catalytic reduction, Nitrogen oxides