The recent decision taken in the USA to further reduce the exhaust emissions from vehicles means a technological challenge for both the designers of engines as well as for the developers of catalytic exhaust aftertreatment systems.
A powerful approach is the simultaneous optimization of the engine raw emissions, of the exhaust pipe and catalytic converter design and of the catalyst formulation. The paper aims at demonstrating this by means of two examples.
New washcoat formulations for Platinum/Rhodium and for Palladium/Rhodium based monolithic catalysts were developed to reach both an improved conversion performance and a better durability.
These catalysts were first evaluated in a model gas reactor using different hydrocarbon species, which were defined by detailed analysis of the vehicle raw emissions during the FTP-75 test cycle. The catalysts were then evaluated on an engine dynamometer, in the fresh and the engine aged state.
For engine aging, several cycles were evaluated to assess the more stringent durability requirements.
Finally the new catalytic exhaust aftertreatment systems were evaluated in the FTP-75 vehicle test procedure using Asian manufactured cars representative of the compact and of the midsize class. In both cases, the new catalytic systems reached emission limits and longer durability which are planned to be introduced in the USA as of model year (MY) 1994.