Selective Catalytic Reduction of Nitric Oxide with Propylene over Fe/Beta Catalysts Under Lean-Burn Conditions

Fe/Beta catalysts were used for the selective catalytic reduction of nitric oxide with propylene (C 3H 6-SCR) under lean-burn conditions, which were prepared by liquid ion-exchange (LIE), solid-state ion-exchange (SIE), and incipient wet-impregnation (IWI) methods. The iron species on Fe/Beta were characterized and identified by a combination of several characterization techniques. The results showed preparation methods had a significant influence on the composition and distribution of iron species, LIE method inclined to produce more isolated Fe 3+ ions at ion-exchanged sites than IWI and SIE method. C 3H 6-SCR activity tests demonstrated Fe/Beta(LIE) possessed remarkable catalytic activity and N 2 selectivity at temperature 300–450 °C. Kinetic studies of C 3H 6-SCR reaction suggested that isolated Fe 3+ species were more active for NO reduction, whereas Fe 2O 3 nanoparticles enhanced the hydrocarbon combustion in excess of oxygen. According to the results of in situ DRIFTS, more isolated Fe 3+ sites on Fe/Beta(LIE) would promote the formation of the key intermediates, i.e., NO 2 adspecies and formate species, then led to the superior C 3H 6-SCR activity. The slight decrease of SCR activity after hydrothermal aging of Fe/Beta(LIE) catalyst might be due to the migration of isolated Fe 3+ ions into oligomeric clusters and/or Fe 2O 3 nanoparticles. View Full-Tex