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During combustion, organosulfur compounds typically contained in gasoline are converted to SO2. Over automotive emission control catalysts, the SO2 can be converted to other sulfur compounds such as H2S,COS, and H2SO4. The chemistry of sulfur over catalysts is a function of A/F as well as catalyst composition. Exhaust emission control catalysts are also poisoned by exhaust SO2. The present study probes the extent of poisoning as a function of A/F, fuel sulfur levels and noble metal composition. The effect of fuel sulfur levels (14-6000 ppm) during aging and evaluation of platinum/rhodium, palladium/rhodium and palladium-only three-way control catalysts was evaluated. Performance measurements are reported for both engine dynamometer and vehicle systems.

The dual requirement of high conversion efficiency and 50K mile durability for cordierite ceramic converters is achievable through optimization of washcoat and catalyst formulation. This paper presents new data for high temperature physical properties, light-off performance, conversion efficiency and pressure drop through an oval cordierite ceramic converter with triangular cell structure and two different washcoat formulations; namely standard vs high-tech. Both of the washcoat systems have a beneficial effect on strength properties with nominal impact on thermal shock resistance. Both the standard and high-tech catalysts provide identical light-off performance for CO, HC and NOx conversion. The high-tech washcoat and catalyst system, in particular, provides consistently superior conversion efficiency for CO, HC and NOx. The pressure drop across the catalyst depends on hydraulic diameter and is only 8% higher for high-tech washcoat than for standard washcoat.

Strict mobile source emission legislation in many countries throughout the world are motivating research and development efforts to bring forth advanced formulations. Steep rises in the price of rhodium during the past couple of years is resulting in intense efforts to control the costs of the new catalyst technologies being developed. This paper examines some catalyst development strategies being explored to accomplish the above objectives.

The first catalytic converters for the control of automotive exhaust emissions were commercialized fifteen years ago in 1974. Since then great progress has been made in improving emissions technology and expanding the options available to the engineer to solve complex emissions problems. This paper traces some of those developments particularly focusing on lower noble metal cost options. Both oxidation and three-way control approaches will be examined. Emphasis will be directed towards the utilization of the relatively low cost noble metal palladium for both types of application.

Experimental dual bed pelleted and monolithic automotive emission control catalysts were prepared and aged on an engine-dynamometer under identical conditions. The catalysts contained the same noble metal loadings and had the same noble metal ratios. The warmed-up conversion performance was obtained for both the front bed catalyst only and for the two catalyst beds in combination. The contaminant pickups and penetrations into the pellets were also measured.