Catalytic decomposition of N2O over Fe-ZSM-11 catalysts prepared by different methods: Nature of active Fe species

A series of Fe-ZSM-11 catalysts were prepared by different methods and tested in N2O decomposition. First, Fe-ZSM-11 catalysts with different Si/Al ratios (15, 25, 36) were prepared by wet ion exchange. The Fe content and catalytic activity were highest for the catalyst with Si/Al ratio 15. Additional Fe-ZSM-11 catalysts with higher Fe contents were prepared by semicontinuous ion exchange or by using alkaline-treated ZSM-11 as the precursor for wet ion exchange. While the catalyst prepared by semicontinuous ion exchange showed low activity, the catalyst prepared using alkaline-treated ZSM-11 turned out to be the most active in this study. Relevant characterization was conducted using X-ray diffraction, X-ray fluorescence, inductively coupled plasma, N2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible spectroscopy, 57Fe Mossbauer spectroscopy, magnetization tests, and X-ray photoelectron spectroscopy. Our data indicate that small FeOx nanoparticles and large iron oxide particles are the predominant Fe species, and small FeOx nanoparticles with low nuclearity are the active Fe species.