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Benzene to phenol hydroxylation with N2O over Fe-Beta and Fe-ZSM-5: Comparison of activity per Fe-site

Paper ID Volume ID Publish Year Pages File Format Full-Text
43982 45998 2007 9 PDF Available
Title
Benzene to phenol hydroxylation with N2O over Fe-Beta and Fe-ZSM-5: Comparison of activity per Fe-site
Abstract

Fe-Beta catalysts with iron content of 0.045–2.0 wt.% were studied in the benzene to phenol transformation with N2O and compared to similar Fe-ZSM-5 catalysts to understand the influence of zeolite structure on the Fe-sites activity. The Fe-containing zeolites were prepared either by a direct hydrothermal synthesis or by a post-synthesis Fe deposition followed by activation (steaming or high temperature treatment in He). Total amount of Fe(II) active sites able to form atomic oxygen (O)Fe, from N2O, was quantified by the transient response method at 523 K measuring the released N2. The fraction of the (O)Fe active in CO oxidation was determined via the amount of CO2 released. The catalyst activity in the benzene to phenol transformation over the activated isomorphously substituted Fe-Beta and Fe-ZSM-5 zeolites was directly proportional to the amount of the (O)Fe active in CO oxidation. The turnover frequency (TOF) over Fe-Beta and Fe-ZSM-5 catalysts was found to be close indicating a similarity in the structures of Fe active sites. The observed ∼2-fold difference can be attributed to the influence of the zeolite host lattices. The difference between Fe-Beta and Fe-ZSM-5 was also observed in DRIFT spectra of NO adsorbed on iron sites at room temperature. The bands of NO adsorbed on Fe-Beta and Fe-ZSM-5 were at 1873 and 1878/1891 cm−1, respectively. The areas of these bands correlate with the amount of (O)Fe active in CO oxidation. Comparison of the DRIFT spectra of adsorbed NO on the zeolites with the spectra on some iron containing compounds allowed to attribute the adsorption sites to Fe(II) sites and not to Fe(III) sites.

Graphical abstractFe-Beta and Fe-ZSM-5 were studied in the benzene to phenol transformation with N2O. The activity of isomorphously substituted Fe-ZSM-5 catalysts calculated per a Fe(II) site active in CO oxidation (TOF) was ∼2-fold higher as compared to the TOF of Fe-Beta catalysts. This was attributed to the geometry of Fe(II) active sites which may vary depending on the zeolite host.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Fe-ZSM-5; Fe-Beta; Zeolites; N2O; Benzene hydroxylation; Phenol; Fe active species
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Benzene to phenol hydroxylation with N2O over Fe-Beta and Fe-ZSM-5: Comparison of activity per Fe-site
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 319, 1 March 2007, Pages 128–136
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
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