Advanced Washcoat Technology for PZEV Application 2008-01-0812
In recent years, automobile emission limits have been tightened world wide. PZEV (Partial Zero Emission Vehicle) which is the most stringent regulation has been imposed in California. To meet the strict PZEV regulation, automotive manufacturers are requesting the catalyst system to have quick light-off characteristics and excellent steady state performance with limited precious group metals (PGM) usage due to the strong price pressure. Moreover, the catalyst can not use high cell density substrate for increasing geometric surface area and reducing heat mass, since the backpressure of exhaust system must be decreased to improve the vehicle power for the PZEV application. This paper will present an efficient catalyst formulation that has been designed to maximize the performance with considerably reduce PGM loading. The catalyst washcoat has been optimized by improving the catalyst geometric surface area, gas diffusivity and thermal mass. The catalyst material was also optimized by enhancing thermal stability and oxygen storage capacity (OSC). The developed catalyst system exhibited superior performance to the previous catalyst developed for the 2006 model year vehicle. The final catalyst system represents a PGM usage that is 50% lower than that of the previous generation.