Characterization of the H2/NOx reaction process over the La0.9Ce0.1Co0.9Pd0.1O3-BaO/Al2O3 catalyst

Yu Lyu; Gang Lyu; Xiangyu Dong; Chonglin Song

doi:10.1016/j.jhazmat.2024.134184

Characterization of the H₂/NOx reaction process over the La_0.9Ce_0.1Co_0.9Pd_0.1O₃-BaO/Al₂O₃ catalyst

J Hazard Mater. 2024 May 15:470:134184. doi: 10.1016/j.jhazmat.2024.134184. Epub 2024 Mar 31.

Authors

Yu Lyu¹, Gang Lyu¹, Xiangyu Dong¹, Chonglin Song²

Affiliations

¹ State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China.
² State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China. Electronic address: songchonglin@tju.edu.cn.

PMID: 38569344
DOI: 10.1016/j.jhazmat.2024.134184

Abstract

An excellent textual properties and performance La_0.9Ce_0.1Co_0.9Pd_0.1O₃-BaO/Al₂O₃ catalyst was synthesized. The reaction mechanism of H₂/NOx over the La_0.9Ce_0.1Co_0.9Pd_0.1O₃-BaO/Al₂O₃ catalyst was investigated by temperature programmed reduction/ desorption/ surface reaction (TPR/D/SR) technologies and in-situ diffuse reflectance Fourier transform (DRIFT) technology. The results show that cerium or palladium species are inserted into the cells of LaCoO₃, as well as they synergetic promote the redox properties of the La_0.9Ce_0.1Co_0.9Pd_0.1O₃-BaO/Al₂O₃ catalyst. Surface activated nitrates exist over the La_0.9Ce_0.1Co_0.9Pd_0.1O₃-BaO/Al₂O₃ catalyst, with thermal stable increasing in the order: absorbed N₂O₄ < monodentate nitrates < chelating bidentate nitrates < nitrates unidentate < free ionic nitrates < bulk free ionic nitrates. H₂ preferentially reacted with absorbed N₂O₄ and monodentate nitrates at low temperatures, due to their high activity. The concentration of generated NH₃ from the redox reaction of H₂/NOx achieves the maximum value between 350 and 450 °C over the La_0.9Ce_0.1Co_0.9Pd_0.1O₃-BaO/Al₂O₃ catalyst. Compared with the NOx adsorption process at 50 °C, monodentate nitrates and absorbed N₂O₄ disappeared due to their low thermal stability, chelating bidentate nitrates become stronger, as well as free ionic nitrates converted to bulk free ionic nitrates with higher thermal stability at 350 °C. When H₂ is exposed to NOx species adsorbed on La_0.9Ce_0.1Co_0.9Pd_0.1O₃-BaO/Al₂O₃, chelating bidentate nitrates and bulk free ionic nitrates are consumed gradually, indicating that although the bulk free ionic nitrates own high stability, it also could be consumed by involving in the H₂/NOx reaction at 350 °C. The quantitative H₂/NO reaction experiments confirmed the results of H₂-TPSR and NSR. It is beneficial to the formation of NH₃ when the H₂/NO ratio is more than 2.5. Comparing traditional Pt-BaO/Al₂O₃ catalyst, the La_0.9Ce_0.1Co_0.9Pd_0.1O₃-BaO/Al₂O₃ catalyst exhibit an excellent performance, including considerable NH₃ production property, lower N₂O selectivity, and the precious metal saving.

Keywords: Ammonia generation; Hydrogen; Nitrogen oxides; Perovskite; Redox reaction process.