Active and spectator iron species in Fe/MFI catalysts for benzene selective hydroxylation with N2O

摘要: Abstract The presence and nature of active spectator iron species in Fe/MFI catalysts is analyzed by comparing reactivity physico-chemical properties (by ESR, Mossbauer 29Si-NMR) a series samples pretreated different conditions which part the selectively removed extraction. A large extra-framework (EFW) present inside zeolite channels could be without affecting significantly productivity or selectivity to phenol. This shows that most abundant may identified these are not those responsible for activity. During catalytic reaction further modification occurs with migration EFW positions largest framework (FW) due Fe3+ Fe2+ reduction forming first disordered clustered oxide/hydroxide (ferrihydrite) then nucleate magnetite nanodomains. initial dislodgement FeFW determines an increase phenol productivity. After about 3h reaches nearly constant value, but this residual activity does correlates amount FeEFW evidencing only benzene selective hydroxylation, while very limited possibly associated sites interacting defect suggested (-Si-O)2Fe2+ reacts N2O give rise (-Si-O)2Fe4+=O oxo-type species.