| Autor: |
Hansen, Brian B., Hammershøi, Peter S., Fagerberg, Freja H., Hansen, Simon I., Sjøgren, Xenia B., Vennestrøm, Peter N. R., Jensen, Anker D., Janssens, Ton V. W. |
| Zdroj: |
Emission Control Science and Technology; 20240101, Issue: Preprints p1-9, 9p |
| Abstrakt: |
In diesel vehicles, selective catalytic reduction by ammonia (NH3-SCR) is used to abate the emission of NOx. Traditionally, the SCR catalyst is placed downstream towards the outlet of the exhaust cleaning system, where heating of the SCR catalyst is slow. This leads to a significant emission of NOxduring cold start as it takes time to reach the operating temperature of 180 °C for the SCR catalyst. When the SCR catalyst is placed directly at the engine outlet (close-coupled position), it is heated faster, resulting in lower NOxemissions. However, a close-coupled SCR catalyst is exposed to higher concentrations of unburnt fuel, CO and SO2, compared to the traditional position further downstream. To assess the performance of close-coupled SCR catalysts, Cu-CHA and V2O5-WO3/TiO2-based monolithic SCR catalysts were exposed to NH3-SCR feeds with controlled amounts of CO, propylene, propane, or SO2. WHTC cold start test cycles showed 10–25% lower NOxemissions for the close-coupled position. Exposing the catalysts to 950 ppmvCO or 450 ppmvof propylene results in a reversible decrease of the NOxconversion by 1–2% points or 7–8% points, respectively. The presence of 2 ppmvSO2has a minor effect on the V2O5-WO3/TiO2catalyst, while the NOxconversion for Cu-CHA decreases from 75 to 63% after exposure to 1.6 g SO2/Lcat. The Cu-CHA catalyst can be regenerated by heating to 500 °C. NH3enhances the impact of SO2on the Cu-CHA catalyst, implying that the urea dosing strategy affects the response of a Cu-CHA-based system to SO2. The results indicate that both conventional types of SCR catalysts are suitable for use in the close-coupled position. |
| Databáze: |
Supplemental Index |
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