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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.

With the advent of stricter vehicle emission standards, the improvement of three way catalyst performance and durability remains a pressing issue. A critical consideration in catalyst design is the potential for variations in fuel sulfur levels to have a significant impact on the ability to reach TLEV, LEV, and ULEV emission levels. As a result, a better understanding of the role of PGM composition in the interplay between thermal durability and sulfur tolerance is required. Three way catalysts representative of standard Pd-only, Pd/Rh and Pt/Rh formulations were studied over a variety of aging and evaluation conditions. The parameters investigated included aging temperature, air fuel ratio and sulfur level. Evaluations were performed on a 1994 TLEV vehicle using different sulfur level fuels. The effect of PGM loading was also included within the study.