Identification of nitrites/HONO as primary products of NO oxidation over Fe-ZSM-5 and their role in the Standard SCR mechanism: A chemical trapping study
2014
Ruggeri, Maria Pia | Selleri, Tommaso | Colombo, Massimo | Nova, Isabella | Tronconi, Enrico
We present direct evidence for the formation of nitrites/HONO in the oxidative activation of NO over Fe-zeolites. Exposure of a Fe-ZSM-5+BaO/Al2O3 physical mixture to NO+O2 at 120°C resulted in forming nitrites on Fe-sites and trapping them on BaO via gas-phase equilibrium with HONO. Identification of nitrites was confirmed by: (i) their thermal decomposition to an equimolar mix of NO and NO2 during TPD, (ii) N2 formation during their reaction with NH3 at 120°C, (iii) ex situ IR analysis of the BaO powder after discharge and separation of the mechanical mixture. The reactivity data suggest that nitrites/HONO are intermediates both in the NO oxidation to NO2 and in the Standard SCR reactions.
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