Fe-ZSM-11 magnetic properties: Its relation with the catalytic activity for NO_x SCR with iso-butane and O₂

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• 作者：Oscar A. Anunziata ; Marcos Gó ; mez Costa and Andrea R. Beltramone
• 关键词：Fe-ZSM-11 ; Fe² ; 3+ ; Magnetization ; Catalytic activity ; NO_x SCR
• 刊名：Applied Catalysis A: General
• 出版年：2006
• 出版时间：3 July 2006
• 年：2006
• 卷：307
• 期：2
• 页码：263-269
• 全文大小：308 K

文摘

Feⁿ⁺-ZSM-11 zeolites, with Fe²⁺ and/or Fe³⁺ as active sites prepared by us by reproducible post-synthesis methods showed magnetic properties. Otherwise, they are very important in environmental catalysis for the reduction of NO_x to N₂ with hydrocarbons. The magnetic and catalytic properties of Fe-ZSM-11 samples with different contents of Fe²⁺ and Fe³⁺ were compared. The Fe²⁺-ZSM-11 sample (with 1.8 Fe²⁺ per unit cell) showed the best catalytic activity and greater saturation magnetization than the other samples. The proportion of Fe²⁺ per unit cell allows having higher amount of active sites for the reduction of NO when Fe²⁺ is bonded to the zeolite structure. These Fe²⁺ species bonded to the framework could generate ferromagnetic couples conferring the ferromagnetic behavior to the samples. The saturation magnetization of the other samples is smaller due to the lower amount of couples Fe²⁺–Fe²⁺. When the amount of Fe³⁺ increases, the Fe bonded to the structure as counter ion decreases, forming α-Fe₂O₃ as isolated clusters inactive for the reduction of NO. Mössbauer characterization of Fe²⁺-ZSM-11 showed that the Fe is forming couples (ferromagnetic) in an important amount. XANES studies of Feⁿ⁺-ZSM-11 samples were performed in order to obtain the Fe^2,3+composition.