The simultaneous catalytic reduction of NO and N2O by NH3 using an Fe-zeolite-beta catalyst

An Fe-Zeolite-beta (Fe-BEA) catalyst, composed only of Fe cations or oxocations in charge compensation sites of the zeolite, is active in the simultaneous removal of NO (1500 ppm) and N2O (1000 ppm) by NH3 (2500 ppm) in the presence of O2 (3 vol.%). In temperature-programmed surface reaction (TPSR) experiments (ramp: 10 K min−1 from 423 to 823 K, space velocity: 200,000 h−1), the light-off temperature, at 50% conversion, is shifted to lower values viz. by 20 K for NO (≈590 K) and 40 K for N2O (≈670 K), compared to those found when processing NO and N2O alone. It is proposed that the removal of surface oxygen O*, coming from the interaction of N2O with iron sites, is faster with NO than with NH3. NO2 which is then formed reacts in turn very fast with NO and NH3 through the classical selective catalytic reduction (SCR) of NOx by NH3 in the presence of O2.