Evolution of Fe species during the synthesis of over-exchanged Fe/ZSM5 obtained by chemical vapor deposition of FeCl3
Résumé
The evolution of iron in over-exchanged Fe/ZSM5 prepared via chemical vapor deposition of FeCl3 was studied at each stage of the synthesis. Different characterization techniques (EXAFS, HR-XANES, 57Fe Mössbauer spectroscopy, 27Al NMR, EELS, HR-TEM, XRD, N 2 physisorption, and FTIR spectroscopy) were applied in order to correlate the changes occurring in the local environment of the Fe atoms with migration and aggregation phenomena of iron at micro- and macroscopic scale. Mononuclear isolated Fe-species are formed upon FeCl3 sublimation, which are transformed into binuclear Fe-complexes during washing. During calcination, iron detached from the Brønsted sites migrates to the external surface of the zeolite, finally leading to significant agglomeration. Nevertheless, agglomeration of Fe can be strongly suppressed by adequately tuning the conditions of the calcination.
Mots clés
- x ray absorption fine structure spectroscopy
- aluminum
- ferric chloride
- iron
- iron 57
- zeolite
- adhesion
- article
- X ray diffraction
- chemical analysis
- vaporization
- transmission electron microscopy
- synthesis
- surface property
- spectroscopy
- reaction analysis
- nuclear magnetic resonance
- Mossbauer spectroscopy
- infrared spectroscopy
- electron energy loss spectroscopy
- correlation analysis
- complex formation