Reduction of nitrogen oxides by ammonia over iron-containing catalysts

Selective catalytic reduction (SCR) of NOx by NH3 is an efficient technology for the removal of nitrogen oxides from diesel exhaust. It is a disadvantage that the active component in commercial catalysts, V2O5, is toxic and melts at similar to 650 degrees C. An alternative catalyst system, based on iron as the active component, was developed in this work. For this purpose, a number of supports were taken and impregnated with Fe2O3 and Fe2O3/WO3 by an incipient wetness technique. The synthesized catalysts were tested in a diesel model exhaust using temperature programmed reaction. The screening accomplished to date, resulted in a 5.8 mol.-% Fe2O3/Al2O3 catalyst that exhibited outstanding activity in the temperature range between 150-375 degrees C with selective formation of N-2. However, this catalyst was significantly deactivated by thermal aging at 600 degrees C. In contrast, the activity of the sample with 1.4 mol.-% Fe2O3 and 0.8 mol.-% WOx showed very high thermal stability as well as selective N-2 production over the whole temperature regime, but it had lower SCR activity.