Selective Catalytic Reduction of Nitrous Oxide by Ammonia on Iron Zeolite Beta Catalysts in an Oxygen Rich Atmosphere: Effect of Iron Contents

A series of iron-exchanged zeolite beta (BEA) has been characterized by temperature programmed desorption (TPD) of oxygen and tested in the catalytic reduction of N2O by NH3. TPD of O2 has clearly shown that iron-oxo species formed upon reoxidation by nitrous oxide of Fe2+-BEA are more labile than those generated by calcination in air. In the selective catalytic reduction of N2O by NH3 the conversion of N2O increases until a degree of iron exchange level of 100% and then decreases. In contrast, the intrinsic activity per mole of iron decreases drastically with the increase of iron content. Mononuclear iron-oxo species have been proposed as the most active sites for the reduction of N2O by NH3; binuclear iron-oxo species and iron oxides aggregates are less active.