Structural and electronic promotion with alkali cations of silica-supported Fe(III) sites for alkane oxidation

Dario Prieto-Centurion, Andrew M. Boston, Justin M. Notestein

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Promoters and precursors can control oxide phase, dispersion, and per-site reactivity of supported oxide catalysts. Previously, dispersed FeOx-SiO 2 resulted from Fe3+ ethylenediaminetetraacetate (FeEDTA-) precursors, with NaFeEDTA giving enhanced dispersion and oxidation rates vs. NH4FeEDTA. Here, catalysts were synthesized by sequential alkali deposition and Fe3+ impregnation. At up to 0.9 Fe nm-2 from NH4FeEDTA and equimolar alkali, UV-visible and H2 TPR were consistent with isolated Fe3+ and small FeOx clusters. Omitting alkali, using Fe(NO3)3, or using Fe/alkali >1 gave evidence of larger agglomerates. For Fe/alkali ≤1 on non-porous SiO2, initial turnover frequencies in adamantane oxidation using H2O2 were independent of surface density. TOF increased as 6.3, 8.8, 15.4, and 20.9 (±0.3) ks-1 for Li +, Na+, K+, and Cs+, respectively, increasingly linearly with decreasing electronegativity. These results give a synthesis-structure-function taxonomy with alkali as an electronic and structural promoter of dispersed FeOx species for alkane selective oxidation.

Original languageEnglish
Pages (from-to)77-85
Number of pages9
JournalJournal of Catalysis
Volume296
DOIs
Publication statusPublished - Dec 1 2012

Keywords

  • Alkali promoters
  • EDTA ligand
  • High dispersion
  • Single-site catalyst
  • Supported oxide

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

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