Experimental evidence of the mechanism behind NH3 overconsumption during SCR over Fe-zeolites
Journal article, 2013

Isotope labeled (NO)-N-15 was used to investigate the mechanism of the unusual overconsumption of NH3 during standard SCR over Fe-zeolite, under conditions during which NH3 oxidation with O-2 alone (without NO) was unfavorable. When the Fe-BEA catalyst was exposed to the (NO)-N-15 + (NH3)-N-14 + O-2 gas mixture at 250 and 300 degrees C, the resulting products included (NO)-N-14, a product of (NH3)-N-14 oxidation under SCR conditions. However, (NO)-N-14 was not detected when Fe-BEA was exposed to (NH3)-N-14 + O-2. Since the only source of N-14 derives from (NH3)-N-14, with the labeled gas mixture used, the (NO)-N-14 during SCR must have originated from oxidation of (NH3)-N-14. Furthermore, twice as much (NN)-N-14-N-14 was observed at 300 degrees C under SCR conditions in comparison with NH3 oxidation using O-2 alone. Under SCR conditions, the (NO)-N-14 formed through the unusual oxidation route further reacted with (NH3)-N-14 to produce N-14(2). Thus, for the first time, we have experimental evidence for the unusual overconsumption of ammonia during SCR over Fe-zeolites.



Fe zeolites

Isotopic labeled experiments

Ammonia oxidation


Selective catalytic reduction

Parasitic ammonia oxidation


Radka Nedyalkova

Competence Centre for Catalysis (KCK)

Chalmers, Chemical and Biological Engineering, Chemical Reaction Engineering

K. Kamasamudram

Cummins Inc.

N. W. Currier

Cummins Inc.

Junhui Li

Cummins Inc.

Aleksey Yezerets

Cummins Inc.

Louise Olsson

Chalmers, Chemical and Biological Engineering, Chemical Reaction Engineering

Competence Centre for Catalysis (KCK)

Journal of Catalysis

0021-9517 (ISSN) 1090-2694 (eISSN)

Vol. 299 101-108

Areas of Advance


Subject Categories

Chemical Engineering



More information