Effect of Nb Promoter on the Structure and Performance of Iron Titanate Catalysts for the Selective Catalytic Reduction of NO with NH3

Iron titanate catalysts with variable Nb content was synthesized by the homogeneous precipitation method, and they were applied to the NH3-selective catalytic reduction (SCR). The widest performance temperature window is obtained on the 0.05Nb-0.95Fe-Ti-O catalyst between 200 and 400 degrees C with a NO conversion higher than 90% at a gas hourly space velocity (GHSV) of 50 000 h(-1). The addition of Nb improves the acidity of Fe-Ti-O catalyst while decreasing its reducibility. The excellent performance of 0.05Nb-0.95Fe-Ti-O is attributed to its suitable acidity and reducibility. Both Bronsted and Lewis acid sites over 0.05Nb-0.95Fe-Ti-O catalyst are active in the reaction, and the formation of reactive monodentate nitrate species and cis-N2O22- also promote the performances.