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Within the next decade, all light-duty vehicles in the United States will be required to meet Tier 2 or LEV 2 tailpipe emission standards. As emission standards have tightened over time catalyst systems have increased in cost. The factors that have contributed to the growth in cost include increases in both precious metal content and catalyst volumes. Calibration strategy, catalyst, and substrate technology improvements have also enabled previous emission standards to be met. The recent dramatic fluctuations in precious metal price, coupled with the increasing desire to reduce system cost, have led catalyst companies to develop converter technologies containing decreasing amounts of precious metal, and still meet Tier2/LEV2 standards. In this paper the development of a novel, near base metal, catalyst technology is described. The effects of precious metal support type and catalyst preparation method are reported using model engine bench and vehicle tests.

The FTP HC, CO, and especially NOx emissions of standard Pd Only three way catalysts have been demonstrated to be more sensitive to fuel sulfur content than Pt/Rh, Pd/Rh, and Pt/Pd/Rh catalysts. To understand the interaction between Pd Only three way catalysts and sulfur, a laboratory study was conducted to examine the relationships between washcoat composition, washcoat structure, and catalyst activity under various evaluation sulfur conditions. First, Pd promoters were examined for their ability to increase activity under both low and high sulfur test conditions. Second, an examination of catalyst structure demonstrated that control of the interaction between Pd and the stabilized ceria washcoat component is critical to achieving high catalyst activity under both low and high sulfur test conditions.

This paper describes the use of advanced three-way catalysts to meet future European and California low emissions legislation. Firstly, it describes the performance of these catalysts tested using the European Stage II test cycle and contrasts their emissions performance over the proposed European Stage III test. The future legislation requires fast catalyst light-off for the low emissions standards to be achieved, therefore the performance of close-coupled catalysts was investigated. The close-coupled catalyst systems gave very low emissions. Space constraints often preclude the use of large volume close-coupled catalysts, and the combination of a small starter catalyst with an underfloor catalyst was tested. This gave performance levels better than the close-coupled configuration. The effect of reducing the underfloor catalyst volume is also described. The work was carried out on a 1.2 litre European Vehicle, the conclusions were verified on a 1.6 litre European vehicle.