EPR Study of Iron-Doped MFI Zeolite and Silicalite Catalysts: Effect of Treatments after Synthesis (Articolo in rivista)

Type
Label
  • EPR Study of Iron-Doped MFI Zeolite and Silicalite Catalysts: Effect of Treatments after Synthesis (Articolo in rivista) (literal)
Anno
  • 2002-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.1163/156856702320267046 (literal)
Alternative label
  • Ferretti A.M., Forni L., Oliva C., Ponti A. (2002)
    EPR Study of Iron-Doped MFI Zeolite and Silicalite Catalysts: Effect of Treatments after Synthesis
    in Research on chemical intermediates (Print)
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Ferretti A.M., Forni L., Oliva C., Ponti A. (literal)
Pagina inizio
  • 101 (literal)
Pagina fine
  • 116 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
  • 28 (literal)
Rivista
Note
  • ISI Web of Science (WOS) (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • Istituto di Scienze e Tecnologie Molecolari, Consiglio Nazionale delle Ricerche, Via Golgi 19, 20133 Milano, Italy, and Dipartimento di Chimica Fisica ed Elettrochimica, UniVersita` degli Studi di Milano, Via Golgi 19, 20133 Milano, Italy (literal)
Titolo
  • EPR Study of Iron-Doped MFI Zeolite and Silicalite Catalysts: Effect of Treatments after Synthesis (literal)
Abstract
  • The systematic study of iron-doped MFI zeolite and MFI silicalite by X- and Q-band EPR spectroscopy is reported in this paper. Both samples, which contain Fe(III) ions in the MFI lattice, underwent three sequential treatments--calcination, steaming, and washing with sodium dithionite solution--which are needed to make the catalyst active by extracting iron ions from the lattice. EPR spectra could be simulated by assuming a broad distribution of spin-spin (zero-field) coupling parameters. The simulation parameters depend on sample history and reproduce the selective intensity changes that are observed in X-band spectra after each treatment. In particular, the distribution width decreases by calcining and steaming samples and then it increases by treating with aqueous dithionite solution. This is in agreement with the view that iron ions are extracted from the framework by calcining and by steaming and may form relatively large iron oxide particles which become smaller after the chemical treatment. We have also studied the temperature dependence of the EPR spectra. The most interesting results are from the steamed samples. Their behavior has been interpreted as due to the presence of superparamagnetic single domain particles of iron oxide. This agrees with the view that iron oxide particles form during steaming. (literal)
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