N2 Selectivity of NO Reduction by NH3 over MnOx鈥揅eO2: Mechanism and Key Factors

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• 作者：Shijian Yang ; Yong Liao ; Shangchao Xiong ; Feihong Qi ; Hao Dang ; Xin Xiao ; Junhua Li
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：September 18, 2014
• 年：2014
• 卷：118
• 期：37
• 页码：21500-21508
• 全文大小：536K
• ISSN：1932-7455

文摘

In this work, the novel relationships of N₂ selectivity of NO reduction over MnO_x鈥揅eO₂ with the gas hourly space velocity (i.e., GHSV) and the reactants鈥?concentrations were discovered. Meanwhile, the mechanism of N₂O formation during the low temperature selective catalytic reduction reaction (SCR) over MnO_x鈥揅eO₂ was studied using in situ DRIFTS study and the transient reaction study. N₂O formation over MnO_x鈥揅eO₂ mainly resulted from the Eley鈥揜ideal mechanism (i.e., the reaction between overactivated NH₃ and gaseous NO), and the Langmuir鈥揌inshelwood mechanism (i.e., the reaction between adsorbed NH₃ species and adsorbed NO_x) did not contribute to N₂O formation. There was an excellent linear relationship of NO reduction and N₂ formation with gaseous NO concentration. Meanwhile, the reaction order of N₂O formation with respect to gaseous NO concentration was nearly 1. However, the reaction orders of NO reduction, N₂O formation, and N₂ formation over MnO_x鈥揅eO₂ with respect to gaseous NH₃ concentration were all higher than 0 due to the adsorption competition between NH₃ and NO+O₂. Therefore, N₂ selectivity of NO reduction over MnO_x鈥揅eO₂ remarkably increased with the increase of gaseous NO concentration, and it slightly decreased with the increase of gaseous NH₃ concentration.