Role of iron impurities in formation of electron-accepting sites in H-ZSM-5 zeolites: 15N nuclear magnetic resonance and 15N nuclear magnetic relaxation of adsorbed N2 and N2O

Abstract

¹⁵ N NMR chemical shifts of N₂ and N₂O molecules as well as ¹⁵N relaxation rates of N₂O adsorbed on a series of H-ZSM-5 zeolites, H-Y zeolite, SiO₂ and γ-Al₂O₃ containing controlled quantities of iron impurities have been studied. Unlike the SiO₂, γ-Al₂O₃ and H-Y samples, the H-ZSM-5 zeolites have strong electron-accepting sites formed by Fe³⁺ and probably Al³⁺ cations. The possible structure of acidic sites and the geometry of the complexes formed during N₂O adsorption are discussed.