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

• Published in: Applied catalysis. B, Environmental Vol. 101; no. 1-2; pp. 61 - 67
• Main Authors: Sultana, Asima, Nanba, Tetsuya, Haneda, Masaaki, Sasaki, Motoi, Hamada, Hideaki
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 22.11.2010; Elsevier
• Subjects: Ammonia; Catalysis; Chemistry; Cu+/Cu2; Cu/ZSM-5; Exact sciences and technology; General and physical chemistry; Ion-exchange; Na+ cation; Selective catalytic reduction; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Zeolites: preparations and properties; Ammonia; Cu/ZSM-5; Selective catalytic reduction; Cu+/Cu2; Na+ cation; Nitrogen oxide; Oxygen; Catalytic reaction; Transition metal; Acidity; Nitrates; Conversion; cation; Characterization; Chemical reduction; Infrared spectrometry; Heterogeneous catalysis; Cu; Na; Copper; Catalyst; Environmental protection
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2010.09.007

[Display omitted] ▶ Influence of cations in the zeolite on NOx reduction by NH3 over Cu/ZSM-5 studied. ▶ Cu/0.6NaZSM-5 is more active for NOx reduction with NH3 compared with Cu/HZSM-5. ▶ Na+ cations tailor the Cu+/Cu2+ active species. ▶ Na+ cation also enhances intermediate nitrogen oxides formation. ▶ Higher amount of active Cu+ species in Cu/NaZSM-5 leads to higher activity. 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.