Effect of Manganese Loading on Catalytic Performance of Mn-K2CO3/γ-Al2O3Catalysts for NSR

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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.

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	Articles by authors
	Zhang Chengwu
	Ding Tong
	Zha Yuqing
	Tian Ye
	Li Xingang

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

Received 2016-04-13;

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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,V35(2): 9-15

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