n-Heptane As a Reducing Agent in the NOx Removal over a Pt–Ba/Al2O3 NSR Catalyst

The reduction with n-heptane of gaseous NO and NOx stored over a model PtBa/Al2O3 catalyst is investigated in this paper by transient microreactor flow experiments coupled with in situ FT-IR spectroscopy for the analysis of the surface species. It is found that n-heptane is an effective reductant of both gaseous NO and stored NOx at temperatures above 200 and 250 °C, respectively. The reduction leads to the selective formation of N2 above 300 °C, whereas significant amounts of other species (N2O) are also formed at lower temperatures. A reaction pathway for the reduction of stored NOx is suggested where n-heptane initially reduces the oxygen-covered Pt sites. This leads to the activation/destabilization of the stored NOx, leading to the NOx release. Released NOx dissociate over Pt sites into N- and O-adatoms: the O-adatoms are scavenged by the hydrocarbon leading to COx and H2O, whereas N-adatoms may recombine with undissociated NO molecules, with other N-adatoms, or with H-ad-species to give N2O, N2, and...

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