New Insights into the N2O Formation Mechanism over Pt-BaO/Al2O3 Model Catalysts Using H2 As a Reductant

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• 作者：Jinxin Zhu ; Jun Wang ; Jianqiang Wang ; Liangfang Lv ; Xiuting Wang ; Meiqing Shen
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：January 6, 2015
• 年：2015
• 卷：49
• 期：1
• 页码：504-512
• 全文大小：680K
• ISSN：1520-5851

文摘

The N₂O formation mechanism was investigated over a Pt-BaO/Al₂O₃ catalyst applied on light-duty diesel vehicles using H₂ as a reductant in the absence and presence of H₂O. In the absence of H₂O, N₂O forms mainly at the initial phase of lean NO_x trapping; while in the presence of H₂O, N₂O appears mainly at the beginning of the rich reduction phase. In the lean period, N₂O is formed via the gaseous NO/O₂ reacting with the adsorbed H and NH₃ that are formed during the previous rich period. The N₂O formation in the rich period is insignificant in the absence of H₂O but is greatly enhanced by the presence of H₂O. The amount of N₂O formed is proportional to the H₂O level in the feed, and its formation is favored at low temperatures. Our FTIR data show that H₂O enhances the rate of nitrite/nitrate reduction during the rich regeneration, which increases the amount of released NO_x, an oxygen source for N₂O formation. Our temperature-programmed experiments indicate that H₂O competes with NH₃ for adsorption sites on Pt surface. This competitive adsorption may increase the NH₃ desorption rate at low temperatures in the rich phase and make Pt surface more accessible to NO.