NOx Abatement by Catalytic Traps: On the Mechanism of NOx Trapping Under Automotive Conditions |
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Authors: | Marcus Hilgendorff |
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Affiliation: | (1) Engelhard Technologies GmbH, Freundallee 23, 30173 Hanover, Germany |
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Abstract: | NOx adsorption was measured with a barium based NOx storage catalyst at an engine bench equipped with a lean burn gasoline direct injection engine (GDI). In order to study the influence of gas phase NO2 on the NOx storage efficiency two different pre-catalysts were used: One with excellent NO oxidation activity to produce a high NO2 concentration and another pre-catalyst without NO oxidation activity and therefore high NO concentration at the NOx storage catalyst inlet. Both pre-catalyst had excellent HC and CO conversion efficiency and therefore the CO and HC concentration at the NOx storage catalyst inlet was practically zero. No lean NOx reduction was observed. Under that conditions, experiments with NOx storage catalysts of different length show that a high NO2 inlet concentration did not enhance the NOx storage efficiency. Moreover, we observed reduction of NO2 to NO over the NOx storage catalyst. However, in presence of a high NO inlet concentration NO2 formation was observed which may proceed parallel to NOx storage. |
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Keywords: | GDI lean NOx trap engine bench NOx adsorption NO2 |
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