In situ FTIR investigation of the role of surface isocyanates in the reduction of NO_X by CO and C₃H₆ over model Pt/BaO/Al₂O₃ and Rh/BaO/Al₂O₃ NO_X storage and reduction

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• 作者：Christopher D. DiGiulio ; Vasileios G. Komvokis ; Michael D. Amiridis ; ^{amiridis@engr.sc.edu}
• 关键词：NOX storage-reduction (NSR) ; Lean NOX traps (LNT) ; FTIR spectroscopy ; Surface isocyanates
• 刊名：Catalysis Today
• 出版年：2012
• 期刊代码：13_09205861
• 类别：ce
• 出版时间：30 April, 2012
• 卷：184
• 期：1
• 页码：8-19
• 文件大小：2173 K

摘要

Monometallic Pt- and Rh-containing model NO_X storage and reduction (NSR) catalysts were investigated by in situ FTIR spectroscopy in order to determine the type of species present on the surface under simulated lean exhaust conditions and to identify potential reaction intermediates during reduction by CO and propylene. The effect of precious metal selection, temperature, and water presence on the NO_X storage and reduction chemistry was considered. The formation of surface isocyanate (NCO) species was observed during all cycling experiments, even in the presence of H₂O, which prompted additional investigation on the role of these species in the NO_X reduction mechanism. Stability and reactivity experiments with BaO/Al₂O₃, Pt/BaO/Al₂O₃ and Rh/BaO/Al₂O₃ confirmed that the reactions of NCO with NO and O₂ - producing N₂ - are metal catalyzed pathways, while the reaction of NCO with H₂O - producing NH₃ - is not. The contribution of NCO-related pathways to the overall N₂ production mechanism could be significant, since quantification of the FTIR results suggests that up to 30%of the total N₂ produced could be directly related to the reaction of surface isocyanates with O₂.