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A two-brick gasoline engine aftertreatment system with advanced washcoat technology was developed for LEV2 PZEV2 legislation, and its application to the upcoming LEV3 SULEV30 emission standard was demonstrated. The system was comprised of 1) a palladium only catalyst in the close coupled position with improved catalytic performance and high phosphorus poisoning resistance compared with 09MY technology, and 2) an underfloor palladium rhodium catalyst technology in which the nitric oxides (NOx) reduction activity was enhanced by preventing the deactivation of rhodium under rich conditions. As a result, the palladium only + palladium rhodium catalysts system met the LEV2 PZEV standard with three quarters of the PGM and half the rhodium of the system used on the Honda 09MY Accord vehicle. The system was also demonstrated to meet the LEV3 SULEV30 standard with some margin.

Environmental problems have raised much attention recently. Automotive manufacturers are strongly required to suppress tailpipe emission world wide. To meet tight legislations such as PZEV and EU5 which are stringent regulation, it is well known that improving the quick light-off performance and hot-NOx conversion are critical issues with limited precious group metals (PGM) usage. Due to the strong pressure of recent PGM prices, further PGM reduction is strongly required for tight regulation applications. Moreover, there is a requirement of utilizing lower cell density substrates to decrease catalyst backpressure for the improvement of vehicle drivability. This paper will present a newly designed formulation that has excellent quick light-off and NOx reduction performance. In the developed catalyst, new thermally stable OSC material and porous washcoat technologies were adopted. Also, the washcoat loading of the catalyst was lowered against current formulations.

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.