NH₃-SCR on Cu, Fe and Cu + Fe exchanged beta and SSZ-13 catalysts: Hydrothermal aging and propylene poisoning effects

Cu, Fe and Cu + Fe ion exchanged Beta and SSZ-13 catalysts were prepared by solution ion exchange using commercial NH₄/Beta, and NH₄/SSZ-13 that was prepared in-house. To study hydrothermal aging effects, Beta supported catalysts were aged hydrothermally at 700 °C and SSZ-13 supported catalysts were aged at 750 °C. In order to reveal the effects of Fe addition in the co-exchanged catalysts, these catalysts were characterized by means of powder X-ray diffraction (XRD), N₂ adsorption-desorption, electron paramagnetic resonance (EPR), ²⁷Al-nuclear magnetic resonance (²⁷Al-NMR) and propylene coking followed with temperature programmed reaction (TPR), and further tested with standard NH₃-SCR with and without the presence of propylene. Collectively, the catalyst characterizations and reaction testing indicated minor beneficial effects of Fe addition in Cu,Fe/Beta, where NH₃-SCR activity, N₂ selectivity and hydrothermal stability were all slightly improved. In contrast, Fe addition did not show apparent beneficial effects in low-temperature SCR for the Cu,Fe/SSZ-13 case. In conclusion, at elevated reaction temperatures, however, the presence of Fe indeed considerably improved NO conversion and N₂ selectivity for the hydrothermally aged Cu,Fe/SSZ-13 catalyst in the presence of propylene.