Physicochemical Characterization of Isomorphously Substituted FeZSM-5 during Activation

Direct conversion of methane under nonoxidative conditions

“…The TMI species may reside in different locations and in various forms in a TMI-modified zeolite catalyst. They might exist as isolated ions in framework positions (isomorphously substituted) or in cationic forms in exchangeable sites or in binuclear and oligonuclear complex in extraframework positions, as oxide in nanoparticles < 2 nm in size, or as large oxide particles in a wide distribution located at the surface of the zeolite crystals [64]. Having control over the distribution of the TMI species on/in the zeolite and over their particle size is certainly an important way to influence the catalyst's activity and selectivity.…”

Reactivity of Fe-binuclear complexes in over-exchanged Fe/ZSM5, studied by in situ XAFS spectroscopy Part 1: Heat treatment in He and O2

“…Studies by Ribera et al [5] and Ramírez et al [13], performed on Fe-framework substituted ZSM5, activated by steaming (∼ 0.6 Fe wt%), have shown that during the activation treatment different Fe species are formed. These species vary from isolated extra framework Fe oxo-ions and oligonuclear oxo-iron complexes located in the zeolite channels to larger highly dispersed iron-oxide nanoparticles on the external surface of the zeolite.…”

Kβ-Detected XANES of Framework-Substituted FeZSM-5 Zeolites

“…Usually a variety of species is formed: isolated extraframework Fe oxo-ions (Fe 1 ), binuclear oxo-iron complexes (Fe 2 ), and oligonuclear oxo-iron complexes (Fe N ) located in the zeolite channels in addition toscatalytically inactiveslarger iron oxide nanoparticles on the external surface of the zeolite (FeO x ). 3 Moreover, part of the iron stays in the framework in inverse relation to the severity of the activation treatment.…”