Nitrogen release from a NOx storage and reduction catalyst

In a NOx storage and reduction (NSR) catalyst, the release and reduction of NOx occurs over a very short period. The speed of the NO, release and reduction creates difficulties in analyzing the chemistry using normal analytical techniques, which are typically better suited to slower, steady-state studies. We have investigated the time dependence of NO, NO2, NH3, N2O and N-2 released by an NSR catalyst using a combination of FT-IR and gas chromatographic techniques. Nitrogen was detected with the GC by using He rather than N-2 as the background gas. The FT-IR was used not only to monitor NO, NO2, NH3 and N2O, but also to establish cycle-to-cycle reproducibility. Under these conditions we used the GC to sample the effluent at multiple times over many lean-rich cycles. To the extent that the chemistry was truly periodic and reproducible, we obtained the time dependence of the release of nitrogen after the lean-to-rich transition. Similar information was obtained for O-2, H-2 and N2O, Combining the FT-IR and GC data, we obtained good cycle averaged nitrogen balances, indicating that all the major products were accounted for. (c) 2006 Elsevier B.V. All rights reserved.