Search Results

Control of N2O emissions is a significant challenge for manufacturers of HDD On-Road engines and vehicles due to requirements for NOx control and Green House Gas (GHG) Phases I & II requirements. OEMs continually strive to improve BSFE which often results in increased engine out NOx (EO NOx) emissions. Consequently, the necessity for higher NOx conversions results in increased N2O emissions over traditional SCR and SCR+ASC catalysts systems [1]. This study explores methods to improve NOx conversion while reducing the SCR contribution of N2O across the exhaust after treatment systems. For example, combinations of two traditional SCR catalysts, one Iron based and another Copper based, can be utilized at various proportions by volume to optimize their SCR efficiency while minimizing the N2O emissions. Results show that a proper combination of catalysts volume can significantly reduce N2O levels while simultaneously reaching the highest levels of NOx performance achieved in the study.

New fuel economy standards intensify the power train development for more fuel efficient vehicles worldwide. Different approaches are utilized to improve the fuel efficiency of gasoline engines. Of all concepts, including downsizing plus turbocharging, stratified operation of spray-guided gasoline direct injection (GDI) engines show the greatest fuel savings benefit. A significant challenge for stratified GDI aftertreatment systems is to develop both catalysts and systems that can reduce the high amount and cost of precious metals currently needed to meet performance standards under low exhaust temperature operating conditions. Furthermore, tighter emission standards will exceedingly require high conversion rates for HC, CO and NOx. In this paper the most recently developed catalyst and systems for lean GDI aftertreatment will be compared with serial production EURO 5 systems against future legislated targets.

Significant reduction in Nitrogen Oxide (NOx) emissions will be required to meet LEV III Emissions Standards for Light Duty Diesel passenger vehicles (LDD). As such, Original Equipment Manufacturers (OEMs) are exploring all possible aftertreatment options to find the best balance between performance, robustness and cost. The primary technology adopted by OEMs in North America to achieve low NOx levels is Selective Catalytic Reduction (SCR) catalyst. The critical parameters needed for SCR to work properly are: an appropriate reductant such as ammonia (NH3) typically provided as urea, adequate operating temperatures, and optimum Nitrogen Dioxide (NO2) to NOx ratios (NO2/NOx). The NO2/NOx ratio is mostly influenced by Precious Group Metals (PGM) containing catalysts located upstream of the SCR catalyst. Different versions of zeolite based SCR technologies are available on the market today and these vary in their active metal type (iron, copper, vanadium), and/or zeolite type.

To enable better matching of Diesel Oxidation Catalyst (DOC) properties to aftertreatment system and application requirements, a systematic evaluation of the effects of sulfur poisoning and desulfation was undertaken on a number of Heavy Duty DOC formulations at representative Platinum Group Metal (PGM) loadings. Uniformly coated DOCs having PGM ratios from 1/0 Pt/Pd to 0/1 Pt/Pd with commercial HDD DOC washcoats were evaluated on a Tier 3 Non-Road engine. In addition, a new DOC formulation intended for reduced sulfur sensitivity, a DOC containing zeolite for hydrocarbon (HC) adsorption, and a layered DOC containing both high and low Pt/Pd ratio layers were compared. Two levels of PGM loading were included for three of the uniform sample formulations.

To meet TierII/LEVII emissions standards, light duty diesel (LDD) vehicles require high conversion efficiencies from the Aftertreatment Systems (ATS) for the removal of both Hydrocarbon (HC) and Nitrogen Oxide (NOx) species. The most populous configuration for LDD ATS have the Selective Catalytic Reduction (SCR) catalyst positioned on the vehicle behind the close coupled Diesel Oxidation Catalyst (DOC) and Catalyzed Diesel Particulate Filter (CDPF). This SCR position may require active heating measures which rely on the DOC/CDPF to provide heat through the combustion of HC and CO in the exhaust. Although DOCs are always impacted by their aging conditions, some aging conditions are shown to be both reversible and irreversible.

Advances in diesel engine and catalyst technologies have enabled light passenger vehicles in meeting the most stringent Tier 3/LEV III emission levels and durability requirements. The advancements in diesel aftertreatment catalyst technology have made catalysts more susceptible to low levels of impurities, typically referred to as poisons. Published studies over the last two decades, have shown a significant impact on the performance of catalysts, to the presence of sulfur and other inorganics in fuels and oils. The design of an aftertreatment system (ATS) typically sets limits for lubricant and fuel quality, specific to the geographical region and availability of certain level of regulated fuels. In this study, we investigate a real-world aged diesel vehicle which exhibited deterioration in tailpipe emissions, beyond levels targeted during engineering development.