Substitution of WO 3 in V 2 O 5 /WO 3 –TiO 2 by Fe 2 O 3 for selective catalytic reduction of NO with NH3

To improve N2 selectivity and lower the cost, WO3 in V2O5/WO3–TiO2 was substituted by a low cost composition Fe2O3 for selective catalytic reduction (SCR) of NO with NH3. The SCR reaction over V2O5/Fe2O3–TiO2 mainly followed the Eley–Rideal mechanism (i.e. the reaction between activated ammonia species and gaseous NO). There were two active components on V2O5/WO3–TiO2 for the activation of adsorbed NH3 (i.e. V5+ and Fe3+). The acid sites on V2O5/Fe2O3–TiO2 mainly resulted from the support Fe2O3–TiO2, so the adsorbed NH3 preferred to be activated by Fe3+ rather than by V5+. V5+ on V2O5/Fe2O3–TiO2 could accelerate the regeneration of Fe3+ on Fe2O3–TiO2 due to the rapid electron transfer between V5+ and Fe2+ on the surface, so the activation of adsorbed NH3 by Fe3+ was promoted. As some NH3 adsorbed on V2O5/Fe2O3–TiO2 was not activated by Fe3+, the inactivated NH3 could then be activated by V5+ on the surface. As a result, 2% V2O5/Fe2O3–TiO2 showed excellent SCR activity, N2 selectivity and H2O/SO2 durability at 300–450 °C. Furthermore, the emission of 2% V2O5/Fe2O3–TiO2 to the fly ash can be prevented by an external magnetic field due to its inherent magnetization. Therefore, 2% V2O5/Fe2O3–TiO2 could be a promising low-cost catalyst in NO emission control.