Fe/Beta catalysts were used for the selective catalytic reduction of nitric oxide with\npropylene (C3H6-SCR) under lean-burn conditions, which were prepared by liquid ion-exchange\n(LIE), solid-state ion-exchange (SIE), and incipient wet-impregnation (IWI) methods. The iron species\non Fe/Beta were characterized and identified by a combination of several characterization techniques.\nThe results showed preparation methods had a significant influence on the composition and\ndistribution of iron species, LIE method inclined to produce more isolated Fe3+ ions at ion-exchanged\nsites than IWI and SIE method. C3H6-SCR activity tests demonstrated Fe/Beta(LIE) possessed\nremarkable catalytic activity and N2 selectivity at temperature 300â??450 Degree C. Kinetic studies of\nC3H6-SCR reaction suggested that isolated Fe3+ species were more active for NO reduction, whereas\nFe2O3 nanoparticles enhanced the hydrocarbon combustion in excess of oxygen. According to the\nresults of in situ DRIFTS, more isolated Fe3+ sites on Fe/Beta(LIE) would promote the formation of\nthe key intermediates, i.e., NO2 adspecies and formate species, then led to the superior C3H6-SCR\nactivity. The slight decrease of SCR activity after hydrothermal aging of Fe/Beta(LIE) catalyst might\nbe due to the migration of isolated Fe3+ ions into oligomeric clusters and/or Fe2O3 nanoparticles.
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