Study of a Fe–zeolite-based system as NH3-SCR catalyst for diesel exhaust aftertreatment

The reactivity of a commercial Fe-exchanged zeolite catalyst is herein analyzed in the NH3-SCR (selective catalytic reduction) reactions of interest for industrial applications to the aftertreatment of diesel exhausts. Transient tests, addressing reacting systems of growing complexity (NH3 + O2, NO + O2, NO2 + O2, NH3 + NO + O2, NH3 + NO2 + O2 and NH3 + NO + NO2 + O2) in a representative temperature range, were performed over the catalyst both in the powder form, in order to derive intrinsic kinetic information, and in the form of small core washcoated monoliths. Results were compared to those collected over a commercial extruded V2O5–WO3/TiO2 catalyst. The zeolite system was characterized by: (i) a higher NH3 storage capacity, (ii) a higher activity in NH3 and NO oxidation reactions, (iii) a higher activity in the standard SCR reaction at low temperature, (iv) a higher activity in the fast SCR reaction and (v) a higher selectivity to N2O in the presence of excess NO2.