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The dynamics of the desulfation of a Ba-containing and a K-containing NOx storage catalyst have been investigated. When both catalysts were desulfated using a temperature ramp in exhaust that simulated gasoline exhaust with a 13:1 A/F, the maximum desulfation rate for the Ba-containing catalyst was seen at 620°C, while the maximum for the K-containing catalyst was at 760°C. This is consistent with the widely known fact that K2SO4 is more stable than BaSO4. The BaSO4 decomposed when either hydrogen or water was in the feed, but not when both were absent. The decomposition, therefore, requires hydrogen to be present and the water can provide sufficient hydrogen for the decomposition via the water-gas shift reaction. With either water or hydrogen in the uncycled feed, the primary sulfur compound formed from the decomposition was H2S for both the Ba and K-containing catalysts.

As vehicle fuel economy requirements continue to increase it is becoming more challenging and expensive to simultaneously improve fuel consumption and meet emissions regulations. The Passive Ammonia SCR System (PASS) is a novel aftertreatment concept which has the potential to address NOx emissions with application to both lean SI and stoichiometric SI engines. PASS relies on an underfloor (U/F) SCR for storage of ammonia which is generated by the close-coupled (CC) TWCs. For lean SI engines, it is required to operate with occasional rich pulses in order to generate the ammonia, while for stoichiometric application ammonia is passively generated through the toggling of air/fuel ratio. PASS serves as an efficient and cost-effective enhancement to standard aftertreatment systems. For this study, the PASS concept was demonstrated first using lab reactor results which highlight the oxygen tolerance and temperature requirements of the SCR.

Exhaust Gas Recirculation (EGR) is an extensively applied approach for the engine emission control, which is the most effective for reducing NOX emissions. However, as increasing EGR rate, the burning velocity of LPG mixture will be slow that it impacts the complete combustion and combustion stability. The effects of EGR on the rapid lean-burning and NOX emissions of the LPG engine with EFI is introduced in this paper. Test data showed that the dual-spark plug ignition-based rapid burning system could increase the combustion rate of LPG mixture, and improve the rapid burning process of the LPG engine with EGR. Meanwhile, the excess air rate Φa limits of LPG lean-burning will be largely extended within the whole effective range of EGR rate. At the equivalent running conditions of LPG engine, largely extended EGR rate could restrain the formation of NOX emissions by the high combustion temperature.