Oxygen transfer centers in Fe-FER and Fe-MFI zeolites: redox behavior and Debye temperature derived from in situ Mössbauer spectra

77 and 300 K in situ Mossbauer spectra recorded after redox treatments of Fe-FER and Fe-MFI ferrisilicates are compared. Similar behavior is found for the two catalysts; reversible redox processes can be detected. Oxidation and coordination states are identified after various treatments, and the value of the average Debye temperature is estimated (260 < ΘD < 300 K). Analysis and comparison of data support the assignment of redox centers to Feframework–O–Feextra-framework pairs.