Experimental evidence of the mechanism behind NH3 overconsumption during SCR over Fe-zeolites
Artikel i vetenskaplig tidskrift, 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

Kompetenscentrum katalys (KCK)

Chalmers, Kemi- och bioteknik, Kemisk reaktionsteknik

K. Kamasamudram

Cummins Inc.

N. W. Currier

Cummins Inc.

Junhui Li

Cummins Inc.

Aleksey Yezerets

Cummins Inc.

Louise Olsson

Chalmers, Kemi- och bioteknik, Kemisk reaktionsteknik

Kompetenscentrum katalys (KCK)

Journal of Catalysis

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

Vol. 299 101-108