Effect of Si islands on low-temperature hydrothermal stability of Cu/SAPO-34 catalyst for NH 3 -SCR

Abstract

Abstract The effect of the Si islands on the stability of Cu/SAPO-34 as a selective catalytic reduction (SCR) catalyst during low-temperature hydrothermal treatment (LTH treatment) was experimentally investigated. Cu/TEAOH (high Si islands) and Cu/TEA catalyst (low Si islands) were synthesized and then aged at 70 °C with 30 vol.% H2O for 48 h. Importantly, structure defect of SAPO-34 caused by Si islands could reduce the steric hindrance for H2O attacking. The stability of the SAPO-34 framework and isolated Cu+/Cu2+ ions was negatively correlated with high content of Si islands. After LTH treatment, the characterization results showed that an obvious dealumination occurred in Cu/TEAOH-LTH catalyst, with a great loss of relative crystallinity and Bronsted acid sites. Furthermore, the isolate Cu+/Cu2+ aggregated into CuO species in Cu/TEAOH-LTH catalyst, which accounted for the serious decreasing NH3-SCR activities of Cu/TEAOH-LTH catalyst. The results showed that Cu/TEA catalyst with less Si islands showed a better stability of structure and NH3-SCR activity after LTH treatment.