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The performance of a commercial Cu-zeolite SCR catalyst after differing degrees of hydrothermal aging (aged for 72 hours at 500, 700 and 800°C with 10% moisture balanced with air) was studied by spatially resolving different key reactions using gas-phase FTIR measurements. Gases were sampled along a channel at different positions and analyzed using FTIR, which overcomes the interference of water and nitrogen on ammonia concentration detection encountered in standard mass spectrometer-based spatial resolution measurements. The NO:NO₂ concentration ratio was changed so that the standard (NO:NO₂ = 1:0), fast (NO:NO₂ = 1:1) and NO₂ (NO:NO₂ = 0:1) SCR reactions could be investigated as a function of the catalyst's hydrothermal aging extent. In addition, the effects of hydrothermal aging on the activity of NH₃ and NO oxidation were also investigated. Hydrothermal aging had little effect on NO oxidation activity.

Lean-burn Spark Ignition Direct Injection (SIDI) engines offer potential fuel economy savings, however, lack of cost-effective lean NOx aftertreatment systems has hindered its broad application. Lean NO Trap (LNT) and Urea Selective Catalytic Reduction (SCR) technologies have been widely investigated as possible solutions, but they both have considerable drawbacks. LNT catalysts suffer from high Platinum Group Metals (PGM) cost, poor thermal durability, sulfur poisoning and active SO regeneration requirements. Urea SCR systems require a secondary fluid tank with an injection system, resulting in added system cost and complexity. Other concerns for urea SCR include potential freezing of the urea solution and the need for customers to periodically fill the urea reservoir. In this paper we report a low-cost, high efficiency concept that has the potential to be a key enabler for lean-burn gasoline engines.

A novel urea evaporation and mixing device has been developed to improve the overall performance of a urea-SCR system. The device was tested with a MY2007 Cummins ISB 6.7L diesel engine equipped with an SCR aftertreatment system. Test results show that the device effectively improved the overall NO conversion efficiency of the SCR catalyst over both steady-state and transient engine operating conditions, while NH₃ slip from the catalyst decreased.

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.

Lean-burn SIDI engine technology offers improved fuel economy; however, the reduction of NOx during lean-operation continues to be a major technical hurdle in the implementation of energy efficient technology. There are several aftertreatment technologies, including the lean NOx trap and active urea SCR, which have been widely considered, but they all suffer from high material cost and require customer intervention to fill the urea solution. Recently reported passive NH₃-SCR system - a simple, low-cost, and urea-free system - has the potential to enable the implementation of lean-burn gasoline engines. Key components in the passive NH₃-SCR aftertreatment system include a close-coupled TWC and underfloor SCR technology. NH₃ is formed on the TWC with short pulses of rich engine operation and the NH₃ is then stored on the underfloor SCR catalysts.

With a tighter regulatory environment, reduction of hydrocarbon emissions has emerged as a major concern for advanced low-temperature combustion engines. Currently precious metal-based diesel oxidation catalysts (DOC) containing platinum (Pt) and palladium (Pd) are most commonly used for diesel exhaust hydrocarbon oxidation. The efficiency of hydrocarbon oxidation is greatly enhanced by employing both Pt and Pd together compared to the case with Pt or Pd alone. However, there have been few systematic studies to investigate the effects of the ratio of platinum to palladium on catalytic oxidation over the DOC. The present study illustrates the relationship between the Pt-Pd ratio and catalyst activity and stability by evaluating a series of catalysts with various Pt to Pd ratios (1:0, 7:1, 2:1, 1:2, 1:5, 0:1). These catalysts were tested for their CO and hydrocarbon light-off temperatures under simulated conditions where both unburned and partially burned hydrocarbons were present.

The cold starting and cold-state running cycle (i.e. engine warming up) of gasoline engines are the key points of exhaust emissions formation of modern engines, and also one of the very important targets for the increasingly stringent emissions regulations. The combustion stability in gasoline engine cold starting and warming up will impact the formation of its exhaust emissions. This paper introduces the improvement in cold starting and warming up combustion process for the motorcycle gasoline engine by high-energy, dual-spark plug based rapid burning system. Test results showed that the high-energy, dual-spark plug based rapid burning system was very helpful to rapid ignition under the engine cold starting condition. Meanwhile, because of increasing the burning velocity of the engine mixture, this solution can realize the larger ignition retard and stable combustion process under the engine warming-up condition.