Improvementof the Activity of γ-Fe2O3forthe Selective Catalytic Reduction of NO with NH3at HighTemperatures: NO Reduction versus NH3Oxidization.

Lignite is widelyused as the fuel for coal-fired power plants, and its flue gas temperatureis about 50–100 °C higher than others. V2O5–WO3/TiO2is extremely restrictedin the selective catalytic reduction (SCR) of NO from the coal-firedpower plants burning lignite due to the drop of NOxconversion, low N2selectivity, and volatilityof vanadium pentoxide at high temperatures. Therefore, a more environmental-friendlySCR catalyst with excellent SCR activity and better N2selectivityat 350–450 °C should be developed for this application.In this work, sulfated Fe–Ti spinel catalyst was developedfor the SCR of NO from the coal-fired power plants burning lignite.The drop of NOxconversion at high temperatureswas mainly related to the simultaneous occurrence of the catalyticoxidization of NH3to NO during the SCR reaction. Ti wasincorporated into γ-Fe2O3to decease theoxidization ability of Fe3+on the surface, and the sitesfor −NH2adsorption and the active components for−NH2oxidization were separated after the sulfationto decrease the probability of the collision between −NH2adsorbed and Fe3+on the surface. They both inhibitedthe catalytic oxidization of NH3to NO over γ-Fe2O3. However, the SCR reaction over γ-Fe2O3was simultaneously restrained after the incorporationTi and the sulfation. Therefore, NOxconversionover γ-Fe2O3at high temperatures dependedon the ratio of NH3conversion through the catalytic oxidizationof NH3to NO to that through the SCR reaction. This ratiodecreased after the incorporation of Ti, and it further decreasedafter the sulfation, resulting in an obvious promotion of NOxconversion at high temperatures. Therefore, sulfatedFe–Ti spinel showed excellent SCR activity, N2selectivity,and H2O+SO2durability at 300–450 °C,which was suitable for the application in the coal-fired power plantsburning lignite. [ABSTRACT FROM AUTHOR]