Comparison on the Performance of α-Fe2O3 and γ-Fe2O3 for Selective Catalytic Reduction of Nitrogen Oxides with Ammonia

gamma-Fe2O3 catalyst showed higher catalytic activity than alpha-Fe2O3 in 150-300 A degrees C. Both NH3 and NO (x) species adsorbed and reacted easily on gamma-Fe2O3. However, NH3 adsorbed on alpha-Fe2O3 and then reacted with gaseous NO (x) . Gaseous NO (x) was more easily adsorbed on alpha-Fe2O3 than gaseous NH3, consequently, stable nitrates formed and blocked the active sites, which affected the SCR reaction badly.