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The performance of NO x storage and reduction over 1.5 wt% Pt/20 wt% KNO 3 /K 2 Ti 8 O 17 and 1.5 wt% Pt/K 2 Ti 8 O 17 catalysts has been investigated using combined fast transient kinetic switching and isotopically labelled 15 NO at 350 °C. The evolution of product N 2 has revealed two significant peaks during 60 s lean/1.3 s rich switches. It also found that the presence of CO 2 in the feed affects the release of N 2 in the second peak. Regardless of the presence/absence of water in the feed, only one peak of N 2 was observed in the absence of CO 2 . Gas-phase NH 3 was not observed in any of the experiments. However, in the presence of CO 2 the results obtained from in situ DRIFTS-MS analysis showed that isocyanate species are formed and stored during the rich cycles, probably from the reaction between NO x and CO, in which CO was formed via the reverse water–gas shift reaction. |
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