Co–ZSM-5 catalysts in the decomposition of N₂O and the SCR of NO with CH₄: Influence of preparation method and cobalt loading

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• 作者：Pieter J. Smeets ; Qingguo Meng ; Steven Corthals ; Hugo Leeman ; Robert A. Schoonheydt
• 关键词：Co– ; ZSM-5 ; Nitrous oxide decomposition ; Selective catalytic reduction ; SCR of NO with CH₄ ; Co loading
• 刊名：Applied Catalysis B: Environmental
• 出版年：2008
• 出版时间：1 December 2008
• 年：2008
• 卷：84
• 期：3-4
• 页码：505-513
• 全文大小：1039 K

文摘

Co–ZSM-5 prepared via different methods with Co/Al ratios ranging from 0.03 to 0.83 are investigated in both the direct N₂O decomposition and the selective catalytic reduction (SCR) of NO with CH₄. UV–vis and H₂-TPR are used to get an insight in the active species in these reactions. It is observed that in catalysts with low Co loadings (Co/Al < 0.3) Co is predominantly present as mono-atomic Co species, located at ion exchange positions in ZSM-5. Higher Co loadings result in the formation of different kinds of Co-oxides, which constitute the majority of species in the over-exchanged catalysts (Co/Al > 0.5). The mono-atomic species show the highest activity in the direct decomposition of N₂O, whereas the oxidic Co species do not seem to contribute much to the overall decomposition. In the SCR, the Co-oxide species catalyze the combustion of CH₄ whereas the selectivity towards NO reduction is much increased at low Co loadings. Therefore, over-exchange of Co–ZSM-5 does not seem to be favorable for both the direct N₂O decomposition and the SCR of NO with CH₄. Co/Al ratios <0.3 give the best results both in terms of conversion and activity per Co atom in both reactions.