Close Coupled Catalyst System Design and ULEV Performance After 1050° C Aging

Close coupled catalysts represent a solution being pursued by automotive engineers to meet stringent LEV and ULEV emission standards. Close coupled systems provide fast light-off by utilizing the energy in the exhaust gas rather than energy supplied by an auxiliary source such as an electrically heated catalyst or a burner in the exhaust. Previous close coupled catalyst designs were limited by the temperature capability of the catalyst coatings. A successful close coupled catalyst technology has been developed 'that is resistant to higher temperature deactivation. This technology is able to function well at low temperature during the vehicle cold start when light-off is critical. The close coupled catalyst technology has approached ULEV emission levels after aging at 1050°C for 24 hours. This study will present experimental results for a close coupled catalyst including the selection of catalyst volume, cross sectional area and combination of catalyst technologies. Results on the final configuration showed the potential to approach ULEV emission levels of HC, CO and NO_x on a 1.91 four cylinder engine.