锰负载量对NSR催化剂Mn-K2CO3/γ-Al2O3催化性能的影响

摘要

采用等体积浸渍法制备了一系列非贵金属NO_x储存还原（NSR）催化剂Mn-K₂CO₃/γ-Al₂O₃，考察了不同锰的负载量对NSR催化剂的结构和催化活性的影响，同时考察了水和CO₂对NO_x储存量的影响。应用X射线衍射分析（XRD）、X射线吸收精细结构（EXAFS）、H₂程序升温还原（H₂-TPR）、CO₂程序升温脱附测试（CO₂-TPD）等技术，对催化剂的结构进行表征。结果表明，锰主要是以MnO₂和Mn₃O₄的形式存在，还有少量的Mn₂O₃。随着锰负载量的增加，催化剂对NO_x的氧化还原能力增强，但催化剂的比表面积降低，使K₂CO₃的分散性降低，逐渐由表相K₂CO₃向体相K₂CO₃转变。NO_x的储存量受到催化剂氧化还原能力和K₂CO₃的分散性两方面因素的影响。当Mn/Al₂O₃的质量比为0.10的时候，NO_x的储存量最大，达到1.30 mmol·g^-1，稀燃/富燃条件下，10个循环后，对NO_x的还原效率达到99%以上。向反应气中加入水和CO₂后，储存能力下降，其中CO₂对储存量的影响比水更大。

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	张成伍
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关键词： NO_x储存还原； K₂CO₃；锰； γ-Al₂O₃

Abstract：

A series of noble metal-free Mn-K₂CO₃/γ-Al₂O₃ catalysts for NO_x storage and reduction (NSR) with different Mn loadings were prepared via dry impregnation. The effects of manganese loading on the structure and catalytic activity of the NSR catalysts were investigated, and the effects of H₂O and CO₂ on the NO_x storage capacities were also investigated. The techniques, including X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), temperature-programmed of H₂ reduction (H₂-TPR) and temperature-programmed desorption of CO₂ (CO₂-TPD), were used to characterize the structure of the catalysts. The results showed that manganese was mainly in the forms of MnO₂ and Mn₃O₄, and there is a small amount of Mn₂O₃. With the increase of Mn loading, the NO_x-redox ability of the catalysts was enhanced. However, with the increase of Mn loading, the specific surface area of the catalysts decreased, resulting in the decrease of the K₂CO₃ distribution and the surface K₂CO₃ gradually turned into bulk K₂CO₃. The NO_x storage capacity (NSC) was affected by the two factors of catalyst redox ability and K₂CO₃ dispersion. When the mass ratio of Mn/Al₂O₃ is 0.10, the catalyst has the largest NSC (1.30 mmol·g^-1). After 10 cycles under lean-burn/fuel-rich conditions, the NO_x reduction efficiency reached as high as 99%. The NSC of the catalyst decreased when H₂O and CO₂ were added to the reaction gas, and the effect of CO₂ was larger than that of H₂O.

Keywords： NO_x storage and reduction； K₂CO₃； Mn； γ-Al₂O₃

Received 2016-04-13;

Fund:

天津市自然科学基金（15JCYBJC23000）。

Corresponding Authors: 田野,E-mail:tianye@tju.edu.cn。 Email: tianye@tju.edu.cn

About author: 张成伍(1989-),男,硕士研究生,现从事稀燃氮氧化物储存还原高性能催化剂方面的研究。

引用本文:

张成伍, 丁彤, 查宇清, 田野, 李新刚.锰负载量对NSR催化剂Mn-K₂CO₃/γ-Al₂O₃催化性能的影响[J]. 化学工业与工程, 2018,35(2): 9-15

Zhang Chengwu, Ding Tong, Zha Yuqing, Tian Ye, Li Xingang.Effect of Manganese Loading on Catalytic Performance of Mn-K₂CO₃/γ-Al₂O₃Catalysts for NSR[J]. Chemcial Industry and Engineering, 2018,35(2): 9-15

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