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Title: Iron loading effects in Fe/SSZ-13 NH3-SCR catalysts: nature of the Fe-ions and structure-function relationships

Using a traditional aqueous solution ion-exchange method under a protecting atmosphere of N2, a series of Fe/SSZ-13 catalysts with various Fe loadings were synthesized. UV-Vis, EPR and Mössbauer spectroscopies, coupled with temperature programmed reduction and desorption techniques, were used to probe the nature of the Fe sites. The major monomeric and dimeric Fe species are extra-framework [Fe(OH)2]+ and [HO-Fe-O-Fe-OH]2+. Larger oligomers with unknown nuclearity, poorly crystallized Fe2O3 particles, together with isolated Fe2+ ions, are minor Fe-containing moieties. Reaction rate and Fe loading correlations suggest that isolated Fe3+ ions are the active sites for standard SCR while the dimeric sites are the active centers for NO oxidation. NH3 oxidation, on the other hand, is catalyzed by sites with higher nuclearity. A low-temperature standard SCR reaction network is proposed that includes redox cycling of both monomeric and dimeric Fe species, for SCR and NO2 generation, respectively. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Program for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and locatedmore » at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.« less
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Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 2155-5435; 47953; VT0504000
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: ACS Catalysis; Journal Volume: 6; Journal Issue: 5
American Chemical Society
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
Country of Publication:
United States
selective catalytic reduction; Fe/SSZ-13; Mössbauer; UV-Vis; EPR; temperature-programmed desorption; reaction kinetics; Environmental Molecular Sciences Laboratory