Technical Paper
A Laboratory Study of NOX Reduction During the Rich Operating Period Over a NOX Storage Catalyst
1999-10-25
1999-01-3502
The behaviour of a NOx storage catalyst in powdered form and containing a storage component based on alkaline metal was investigated under rich conditions. Experiments were conducted in a fixed-bed flow reactor with the space velocity set at 45,000 h-1. From these experiments it was possible to extract the fractional NOx reduction and the efficiency of use of the reductant. With 0.9% CO as a reductant at 350°C, complete utilisation of CO was achieved up to 70% NOx conversion as treatment time was increased. To obtain 90% NOx conversion required longer times, and 23% of the CO did not participate in the reduction of NOX. A reductant balance shows that about 40% of the CO added is used to reduce the catalyst surface when the flow is switched from lean to rich. The ranking of efficiencies of different reductant gases at 350°C gave the following sequence: 0.9% H2 ≈ 0.9% CO > 1285 ppm toluene > 3000 ppm propene ≈ 1125 ppm i-octane > 3000 ppm propane.
