Study of the Fe/zeolite-L system: Part I: Characterization of iron species and their structural properties

Zeolite-L in potassic (ZLK) and acidic (ZLH) forms were used as a support for iron species to obtain two solids, called Fe/ZLK and Fe/ZLH, respectively. “In situ” Mössbauer spectroscopy (MS) between room temperature (RT) and 15 K, volumetric oxidation (VO) and thermogravimetric analyses were used to determine the iron species existent after reduction (Fe 0, Fe 2+ and Fe 3O 4) and to study their structural properties. In both solids, a similar fraction of very small Fe 0 crystals was found inside the zeolite channels. Intermediate species, like exchanged Fe 2+, were also detected in both samples. It was possible to determine that Fe 2+ ions are located at sites D in Fe/ZLK and sites A in Fe/ZLH. Soft reduction conditions, like slow temperature raise (2 K/min), allowed to maintain metallic Fe crystals inside the zeolite-L structure in contrast with other Fe/zeolite systems.