Comparison between ammonia and propane as the reducing agent in the selective catalytic reduction of NO under lean conditions over Pt black

The catalytic activity of Pt black towards the reduction of NO under lean conditions is examined. Ammonia and propene are tested as reducing agents. A scrambling between nitrogens is observed in the formation of N-2 and N2O for NH3. For C3H6, a reduction of NO to mainly N2O is found. A minor formation of N-2 is only observed for high C3H6 concentrations. The role of NO2 as an intermediate in the reduction of NO is examined by using a feed gas mixture containing NO2, as well as by studying the catalytic activity of Pt black towards the NO-O-2 and NO2-O-2 reactions. No effect is observed in the maximum NOx conversion for C3H6 whereas for NH3 a decreased activity is found. The presented results are put in perspective of the reaction mechanisms proposed in the literature. (C) 1999 Elsevier Science B.V. All rights reserved.