Sulfur-poisoning and thermal reduction regeneration of holmium-modified Fe-Mn/TiO2 catalyst for low-temperature SCR

The effect of SO2 on the low-temperature SCR activity and the thermal reductive regeneration for holmium-modified Fe-Mn/TiO2 catalyst were investigated by activity assessment and various characterization methods. The deposition of ammonium sulfate ((NH4)2SO4) on catalyst surface and the sulfuration of active component (MnSO4) were proved to be the main causes for the deactivation in the presence of SO2. The catalyst Fe0.3Ho0.1Mn0.4/TiO2 exhibited superior SO2 durability when the concentration of SO2 was lower than 0.04%, and the catalytic activity could markedly recover with the termination of sulfur-poisoning source. The deactivation behavior was irreversible when the concentration of SO2 was increased to 0.1% but the deactivated catalyst could be regenerated after thermal reduction (350°C) for 60 min by 5% NH3. The microstructure and physicochemical properties could be significantly restored after the thermal reductive regeneration. Moreover, the NOx conversion could return to about 80%.