Iron-catalyzed propylene epoxidation by nitrous oxide: Studies on the effects of alkali metal salts

Xiaoxing Wang, Qinghong Zhang, Sufen Yang, Ye Wang

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58 Scopus citations

Abstract

SBA-15-supported iron catalysts with and without alkali metal salt modifications were studied for propylene oxidation by nitrous oxide. The reaction route could be dramatically changed from allylic oxidation to epoxidation by modification of the FeOx/SBA-15 catalyst with alkali metal salts. The KCl-1 wt % FeOx/SBA-15 (K/Fe = 5) catalyst exhibited the best catalytic performances for propylene epoxidation, over which ca. 50% propylene oxide selectivity could be gained at a 10% propylene conversion at 648 K. Characterizations with diffuse reflectance UV-Vis, XANES, and Raman spectroscopic techniques revealed that the modification with KCl increased the dispersion of the iron species and changed the local coordination of iron into a tetrahedral configuration on the inner surface of SBA-15. This tetrahedrally coordinated iron site, which was probably stabilized by potassium ions, was proposed to account for the epoxidation of propylene by nitrous oxide. At the same time, the reactivity of lattice oxygen was inhibited, and the acidity of the FeOx/SBA-15 was eliminated. These changes should also contribute to the increase in the selectivity to propylene oxide. The counteranions in the alkali metal salts exerted a significant influence on the catalytic behaviors probably via an electronic effect.

Original languageEnglish (US)
Pages (from-to)23500-23508
Number of pages9
JournalJournal of Physical Chemistry B
Volume109
Issue number49
DOIs
StatePublished - Dec 15 2005

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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