Effect of FeH-zeolite structure and Al-Lewis sites on N2O decomposition and NO/NO2-assisted reaction

Fe ions in zeolites of ferrierite and beta structures with Fe content of 0.55 wt% and 0.60 wt% and Fe/Al molar ratios of 0.06 and 0.09, respectively, loaded predominantly in cationic sites, with the zeolites also containing controlled amounts of Al-Lewis sites, were used to analyze the effect of Fe–Fe distances and the simultaneous presence of Fe and Al-Lewis sites on direct N2O decomposition and NO/NO2-assisted N2O decomposition. It was found that shorter Fe–Fe distances in ferrierite result in higher N2O conversion in direct N2O decomposition. The presence of Al-Lewis sites in the vicinity of Fe ions also increases the N2O conversion in direct decomposition on Fe ions. In contrast, NO/NO2-assisted N2O decomposition does not discriminate between these effects. It is concluded that the direct N2O decomposition is structurally site-specific and is controlled by the rate of recombination of oxygen atoms bound to Fe sites, whereas NO/NO2-assisted N2O decomposition is controlled by the rate of NO2 → NO conversion occurring on structure-nonspecific Fe sites.