A comparative study of different doped metal cations on the reduction, adsorption and activity of CuO/Ce0.67M0.33O2 (M = Zr4+, Sn4+, Ti4+) catalysts for NO + CO reaction

Authors: Xiaojiang Yao, Qiang Yu, Zeyang Ji, Yuanyuan Lv, Yuan Cao, Changjin Tang, Fei Gao, Lin Dong, Yi Chen

Abstract:
A series of ceria-based solid solutions (Ce_0.67Zr_0.33O₂, Ce_0.67Sn_0.33O₂, Ce_0.67Ti_0.33O₂) were synthesized by inverse co-precipitation, and then used as supports to prepare CuO/Ce_0.67M_0.33O₂ (M = Zr⁴⁺, Sn⁴⁺, Ti⁴⁺) catalysts through wetness impregnation method. The obtained samples were investigated in detail by means of XRD, LRS, N₂-physisorption, H₂-TPR, XRF, XPS and in situ FT-IR techniques. The catalytic reduction of NO by CO as a model reaction was chosen to evaluate the catalytic performance of these samples. These results suggest that: (1) the reduction of CuO/Ce_0.67Zr_0.33O₂ is easier than CuO/Ce_0.67Sn_0.33O₂ and CuO/Ce_0.67Ti_0.33O₂ catalysts, which may be attributed to the difference in the electronegativity of dopant; (2) the reduced state Cu+ is present in CuO/Ce_0.67Zr_0.33O₂ at ambient temperature due to the shifting of redox equilibrium (Cu²⁺ + Ce³⁺ ↔ Cu⁺ + Ce⁴⁺) to right; (3) the adsorbed NO species on CuO/Ce_0.67Zr_0.33O₂ are more liable to desorb/transform/decompose than those on CuO/Ce_0.67Sn_0.33O₂ and CuO/Ce_0.67Ti_0.33O₂ samples. The results of catalytic performance show that Cu⁺/Cu⁰ species play a key role in NO reduction by CO, and the activity is mainly related to the electronegativity of dopant, the reduction and adsorption behaviors of these catalysts. Furthermore, a possible reaction mechanism (schematic diagram) is tentatively proposed to understand this reaction.

Keywords:
Ceria-based solid solution
Dopant
Electronegativity
Copper-based catalyst
NO + CO reaction

Published in: Applied Catalysis B: Environmental (Volumes 130–131, Pages 1-336, 7 February 2013)

Publisher: Elsevier  

ISSN Information: 0926-3373

A comparative study of different doped metal cations on the reduction, adsorption and activity of CuO/Ce0.67M0.33O2 (M = Zr4+, Sn4+, Ti4+) catalysts for NO + CO reaction

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