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The future emission limits for gasoline fuelled passenger cars require more and more efficient exhaust gas aftertreatment devices - the catalytic converter being one essential part of the complex system design. The present paper summarizes the results of several basic research programs putting major emphasis on the application of highly sophisticated three-way catalyst technologies being taylored for the utilization on ultra thin-wall ceramic substrates. In the first part of the investigation the following effects were examined in detail: Different washcoat loadings at constant PGM-loadings Different volumes of catalysts for constant amounts of PGM and washcoat Similar washcoat technologies at different ratios of WC-loading to precious metal concentration in the washcoat.

The exhaust emissions of two and three wheelers contribute to a major extent to the pollution in urban areas of South East Asia and especially India. Most of this class of vehicles are equipped with 2 stroke engines, which operate constantly rich, - leading to high carbon monoxide and hydrocarbon emissions. On the other hand the NOx concentration in the exhaust gas is neglegible. In near future more stringent exhaust gas legislation get effective in a number of countries. Therefore catalytic aftertreatment devices are necessary to meet the emissions limits. Hot Tubes™ and/or monolith type catalysts can be applied. The high exhaust gas hydrocarbon concentrations lead to high exotherms on oxidation which drives the exhaust gas temperatures up to a range between 750 and 850°C. Therefore thermal ageing of the Hot Tubes™ and monolith type catalysts is severe. The design of advanced catalyst systems has to take this into account.

The exhaust emissions of two stroke vehicles like motorbikes and scooters contribute to the pollution in urban areas of developing countries in South East Asia and India to a major extent. But also in Japan and selected European countries exhaust gas limitations become effective from 10/1998 and 06/1999 for these vehicles. To control this emissions catalytic aftertreatment by Hot Tubes® and/or monolith type catalysts are applied. Due to the constant rich operation of the two-stroke engines, common design criteria for three-way catalysts fail. Extremely high exhaust gas hydrocarbon concentrations lead to high exotherms during oxidation which increases the exhaust gas temperature to a range between 800 and 900 °C. Furthermore the lack of oxygen limits the CO and HC oxidation under certain engine operation conditions. Therefore, water-gas shift and steam reforming reactions play an important part in catalytic aftertreatment of two-stroke exhausts.