Search Results

In order to simulate the aging of the emission control system over the life of a vehicle, a variety of engine dynamometer cycles has been developed that accelerate the catalyst aging processes. This paper investigates the sensitivity of automotive emission control catalysts to their aging and testing environments. To show the effects of aging conditions on catalytic performance, three engine stand dynamometer aging cycles were utilized. These aged catalysts were then tested on two test vehicles: one featured multi-point fuel injection; the other, sequential electronic fuel injection. The performance results indicate the sensitivity of a catalyst to aging conditions as well as the various parameters of its operating environment. This sensitivity varied for the two catalyst formulations.

As legislation tightens in the Heavy Duty Diesel (HDD) area it is essential to develop systems with high activity and excellent durability for both Particulate Matter (PM) and NOx control. The Continuously Regenerating Trap (CRT™) system controls hydrocarbon (HC), CO and PM emissions from HDD vehicles with efficiencies of over 90%, and has demonstrated very good field durability over distances exceeding 700,000 km. The system is widely used in Europe, and is demonstrating the same high performance and excellent durability within field applications in North America. The Continuously Regenerating Trap (CRT™) system has been developed and patented by Johnson Matthey [1]. Throughout this paper this system will be referred to as the Continuously Regenerating Diesel Particulate Filter, CR-DPF. The CR-DPF comprises an oxidation catalyst, optimised for NO2 generation from the engine-out NOx, and a downstream DPF.

Extracts of exhaust emissions from passenger cars equipped with conventional and lean-burn gasoline engines were tested for PAHs, NPAHs and mutagenicity. When installed with an appropriate three-way or oxidation catalyst very large reductions in each of these measurements were observed, alongside reductions in regulated emissions and gaseous aldeyhdes. These beneficial effects were apparent over U.S. and European cycles.

The effective use of a catalyst to initiate regeneration of a diesel particulate trap has traditionally been based on the concept that the catalyst coated onto the trap adsorbs particulate, and activates oxygen in the exhaust causing initiation of particulate combustion. Reported regeneration temperatures generally lie in the range of 350°C and above. This paper reports on a new mechanism of diesel particulate combustion involving activation of oxygen over a catalyst to form NO2, which is then capable of adsorbing on diesel particulate trapped in a filter and initiating combustion at lower temperatures. Diesel particulate has been combusted on a wire mesh trap at temperatures as low as 265°C, and this regeneration capability has been maintained over hundreds of hours of operation. However, the most active catalysts for low temperature activation of diesel particulate are also high sulfate producers.

The primary topic of this paper is the evolution of the early oxidation catalysts of the 1960's to present-day sophisticated three-way catalysts. Early catalyst formulations are described, along with the chemistry of catalytic emission control for automobiles. The evolution in catalyst formulations and engine control strategy is discussed at length. Precious metal supply and world emission regulations are discussed briefly. The scope of this paper is primarily limited to the U.S. automotive industry and the U.S. standards.

The tightening NOx and particulate matter (PM) emission standards for heavy duty diesel powered vehicles are stimulating the development of aftertreatment systems to reduce NOx and PM emissions from such vehicles. Here we present data on a new system which combines NO2-based continuously regenerative trap particulate removal technology with urea-based Selective Catalytic Reduction (SCR) NOx removal technology. There are a number of beneficial synergistic effects associated with combining these two technologies, including a significant improvement in the low temperature NOx removal performance of the SCR system. The development of this PM/NOx control system is described, and the main features of this novel strategy are outlined. The PM/NOx control system has been evaluated on a number of different engines and over a number of different drive cycles.

Proposals to further lower particulate matter standards for heavy duty diesel powered vehicles throughout the world, have prompted further interest in particulate filter based aftertreatment solutions. Continuously regenerating traps have been utilised in Europe as a retrofit technology for more than 6 years and this study summarises that experience. Predominantly the growth in the market for the continuously regenerating trap has been in those countries which have promoted the use of ultra-low sulfur diesel fuel (i.e. less than 50 ppm S) - Sweden, Germany, and the UK, and to a lesser extent in another seven countries. A selection of continuously regenerating traps was taken from the field after high road mileage accumulation, up to 600,000 km, and subsequently tested for performance on diesel engine bench dynamometers; the results of these studies are reported and discussed.