1998-02-23

Development of Close-Coupled Catalyst Systems for European Driving Conditions 980663

The present paper describes the results of a joint development program focussing on a system approach to meet the proposed EURO III and IV emission standards for a passenger car equipped with a 3.2 liter, 18 valve gasoline engine. Starting with the in-production configuration of a EURO II certified vehicle (model year 1997) the following improvement points were investigated in detail.By the introduction of a close-coupled catalyst in combination with engine measures to improve the catalyst light-off the proposed EURO III limits were met. The proposed EURO IV hurdle could be overcome by further using secondary air injection during cold-start in combination with an increased precious metal loading for the close-coupled catalyst.In order to take care of the precious metal resources and to become more independant of precious metal price fluctuations, a new developed catalyst coating with an improved activity characteristic after high temperature aging on an engine and on a vehicle was introduced. Furthermore, the application of engine and catalyst measures are described to obtain a better catalyst durability by reducing the catalyst bed temperature during full load engine operation.Future development work will mainly focus on the optimization of the precious metal content including an OBD-control function to monitor the catalyst activity.

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