Simultaneous conversion of nitrogen oxides and soot into nitrogen and carbon dioxide over iron containing oxide catalysts in diesel exhaust gas

Abstract This paper deals with the simultaneous catalytic conversion of NO x and soot into N 2 and CO 2 in diesel exhaust gas. Several iron containing oxide catalysts were partially modified by the alkali metal potassium and were used for NO x –soot reaction in a model exhaust gas. Fe 1.9 K 0.1 O 3 has shown highest catalytic performance for N 2 formation in the so far investigated catalysts. Further studies have shown that Fe 1.9 K 0.1 O 3 was deactivated in a substantial way after about 20 TPR experiments due to the agglomeration of the promoter potassium. Experiments carried out over the aged Fe 1.9 K 0.1 O 3 catalyst have shown that NO x –soot reaction was suppressed at higher O 2 concentration, since O 2 –soot conversion was kinetically favored. In contrast to that, the catalytic activity was increased in presence of NO 2 and H 2 O. Mechanistic examinations suggest that (CO) intermediates, formed at the soot surface, are the reactive sites in the NO x –soot reaction. Higher catalytic performance in presence of NO 2 could be explained by the enhanced formation of these (CO) species. Moreover, nitrate species formed at the catalyst surface might also play an important role in NO x –soot conversion.