The chemistry of DeNOx reactions over Pt/Al₂O₃: The oxime route to N₂ or N₂O

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• 作者：Emmanuel Joubert ; Xavier Courtois ; Patrice Marecot ; Christine Canaff and Daniel Duprez
• 关键词：DeNOx catalysis over Pt ; Organic nitrogen compounds in NO SCR ; Oximes in DeNOx reaction ; Reaction intermediates in catalytic NO reduction
• 刊名：Journal of Catalysis
• 出版年：2006
• 期刊代码：97_00219517
• 类别：ce
• 出版时间：25 October 2006
• 卷：243
• 期：2
• 页码：252-262
• 文件大小：286 K

摘要

The reactivity of 12 nitrogen compounds with different organic functions (nitro, nitrite, nitrate, oxime, isocyanate, amide, amine, nitrile) was investigated over a 1%Pt/δ-Al₂O₃ catalyst (mean metal particle size, 20 nm) in oxygen excess conditions (5%O₂ + 5%H₂O). Two series of experiments, at temperatures ranging from 150 to 500 °C, were carried out: (i) decomposition of the N compounds without any addition of NO and (ii) reduction of NO by these compounds. The results were compared with the catalytic behavior of the Pt catalyst in NO reduction by propene. Some of the N compounds as well as oxygenated products were identified by GC-MS in the NO + C₃H₆ reaction. The nitrogen organic intermediates could be classified into two groups: (i) class 1 compounds, which react with NO at relatively high temperatures (300 °C) with a high selectivity to N₂ (nitro, nitrite, nitrate, nitrile), and (ii) class 2 compounds, which reduce NO in the same temperature range as propene (200–225 °C) with a selectivity of J-4KV8TJY-2&_mathId=mml10&_user=10&_cdi=6852&_rdoc=5&_handle=V-WA-A-W-WD-MsSWYWW-UUA-U-AAZCBUBWEW-AAZWYYVUEW-VBBWWAZZ-WD-U&_acct=C000050221&_version=1&_userid=10&md5=03307c38263f0d76efb2c2a1f92d2db6" title="Click to view the MathML source">≈50% close to that of NO reduction by propene (oximes, amides, amines, and, to a lesser extent, isocyanate). A mechanism is proposed in which oxime species play a key role in NO reduction. N₂O would be produced mainly by a Nef reaction (leading to ketones and N₂O), whereas N₂ would be formed by successive steps starting with a Beckmann rearrangement of oxime species, with the byproducts of the N₂ formation being acids, alcohols, and nitrato and nitrito species.