The improving effect of SO42− on environmental-friendly SO42−/α-Fe2O3 catalyst for NH3-SCR

For the selective catalytic reduction (SCR) of NOx by NH3, a variety of SO42−/α-Fe2O3 catalysts were created and utilized. The consequences manifest that the sulfation treatment signally boosted the NOx conversion of α-Fe2O3. With varying SO42− loadings, the T90 of SO42−/α-Fe2O3 catalysts ranges from 10% SO42−/α-Fe2O3 (301 °C) > 15% SO42−/α-Fe2O3 (306 °C) > 5% SO42−/α-Fe2O3 (314 °C) > 20% SO42−/α-Fe2O3 (321 °C). The optimum concentration of sulfate treatment samples was 10% wt., producing approximately 100% NOx conversion at 325–400 °C. Although the introduction of SO42− weaken the redox capacity of α-Fe2O3, the quantity and strength of acidic sites on SO42−/α-Fe2O3 was dramatically enhanced. Meanwhile, introducing SO42− to α-Fe2O3 hindered the ammonia oxidation process and increased the pore volume of the catalyst, enhancing SCR activity. In situ DRIFTS investigations demonstrated that NH3 adsorbed on Brønsted acid sites displayed better stability over SO42−/α-Fe2O3 catalysts. Due to the decreased capacity of the catalyst surface to adsorb NOx, the E-R route prevails on 10% SO42−/α-Fe2O3 catalyst.