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

• Main Authors: Hao Zhou, Mengyao Ge, Huishuang Zhao, Shiguo Wu, Mengyu Li, Yaxin Su
• Format: Article
• Language: English
• Published: MDPI AG 2019-02-01
• Series: Catalysts
• Subjects: NO; SCR; C₃H₆; Fe/Beta; Iron species
• Online Access: https://www.mdpi.com/2073-4344/9/2/205

Fe/Beta catalysts were used for the selective catalytic reduction of nitric oxide with propylene (C₃H₆-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 Fe³⁺ ions at ion-exchanged sites than IWI and SIE method. C₃H₆-SCR activity tests demonstrated Fe/Beta(LIE) possessed remarkable catalytic activity and N₂ selectivity at temperature 300⁻450 °C. Kinetic studies of C₃H₆-SCR reaction suggested that isolated Fe³⁺ species were more active for NO reduction, whereas Fe₂O₃ nanoparticles enhanced the hydrocarbon combustion in excess of oxygen. According to the results of in situ DRIFTS, more isolated Fe³⁺ sites on Fe/Beta(LIE) would promote the formation of the key intermediates, i.e., NO₂ adspecies and formate species, then led to the superior C₃H₆-SCR activity. The slight decrease of SCR activity after hydrothermal aging of Fe/Beta(LIE) catalyst might be due to the migration of isolated Fe³⁺ ions into oligomeric clusters and/or Fe₂O₃ nanoparticles.