Influence of co-cations on the formation of Cu⁺ species in Cu/ZSM-5 and its effect on selective catalytic reduction of NOx with NH₃

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• 作者：Asima Sultana ; Tetsuya Nanba ; Masaaki Haneda ; Motoi Sasaki ; Hideaki Hamada
• 关键词：Selective catalytic reduction ; Ammonia ; Cu/ZSM-5 ; Na⁺ cation ; Cu⁺/Cu²⁺
• 刊名：Applied Catalysis B: Environmental
• 出版年：2010
• 出版时间：22 November 2010
• 年：2010
• 卷：101
• 期：1-2
• 页码：61-67
• 全文大小：598 K

文摘

The influence of H⁺ and Na⁺ co-cations on the formation of Cu species and on NO reduction activity of Cu/ZSM-5 catalyst is investigated. 3.5Cu/0.6NaZSM-5 catalyst was significantly more active for NOx reduction with NH₃ compared with 2.6Cu/HZSM-5. Catalyst characterization indicated that, the type of co-cations present in the catalyst tailors copper species redox properties, NO₂ formation rate and acidity of the catalyst. Copper species in NaZSM-5, is relatively easily reducible than when present in HZSM-5. UV–vis and FTIR characterization showed the presence of a higher amount of Cu⁺ species in 3.5Cu/0.6NaZSM-5 compared to 2.6Cu/HZSM-5. The easily reducible copper along with Cu⁺ species in 3.5Cu/0.6NaZSM-5 seems to activate oxygen which reacts with NO to form NO₂. The Na⁺ co-cations can further capture the thus produced NO₂ to form intermediate surface nitrite/nitrate species, which improves the NOx conversion. The acidity measured by NH₃-TPD and FTIR is needed for SCR, but not crucial for NOx conversion.