Selective catalytic reduction of NOx with NH3 (NH3-SCR) was investigated over a series of Fe-containing samples prepared by the coprecipitation method. The doping effect of introducing representative cations (M = Ti4+, Ce3+/4+, Al3+) with apparent different acidity and redox properties was systematically studied. The results indicated that suitable acidity and redox property as well as the balance between them were extremely important for the NH3-SCR reaction. Ti4+-doped catalysts showed the most prominent effect, obtaining 4-fold increase in NOx conversion compared to Fe2O3 at 100 degrees C, due to their strong acidity and slight reducibility. Samples with Ce3+/4+ doping, which could be facilely reduced but lacked sufficient acidity, showed lower catalytic activity than Al3+-doped samples with relatively stronger acidity. Thus, the activity followed Fe9Ti1Ox > Fe(9)Al(1)Ox > Fe9Ce1Ox. In addition, the Fe(9)Ti(1)Ox catalyst exhibited an similar to 80% NOx conversion and remained stable in the presence of SO2 and H2O at 250 degrees C for 80 h, making it a suitable candidate for the NH3-SCR reaction.