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Catalytic emission control systems are installed on nearly all automobiles and heavy-duty trucks produced today to reduce exhaust emissions for the vehicles to meet government regulations. Current systems can achieve very high efficiencies in reducing tailpipe emissions once the catalytic components reach their operating temperatures. They are, however, relatively ineffective at temperatures below their operating temperature windows, especially during the cold start period of the vehicles. With the increasingly stringent government regulations, reducing the emissions during the cold start period before the catalytic components reach their operating temperatures is becoming a major challenge. For cold start HC control, HC traps based on zeolites have been investigated and commercialized for certain applications. For cold start NOx control, especially in lean burn engine exhaust, NOx storage and release catalysts have been evaluated.

This paper describes the development and characterization of a selective catalytic reduction (SCR) catalyst system for a typical EUIV heavy-duty diesel (HDD) engine. The performance of the SCR catalyst and the impact of catalyst volume are described. The effect of using an ammonia slip catalyst behind the SCR catalyst is investigated, before examples of the use of computer modelling to refine the optimum volume and urea injection strategy are given. Finally, the durability of the SCR catalyst is described. Taken as a whole, the results demonstrate how a combination of practical experiments and computer modelling can be used to refine the system and provide a cost-effective exhaust aftertreatment (EA) solution.

This paper describes the development and characterization of a Selective Catalytic Reduction (SCR) catalyst system for EUIV (HDD) engines. The performance of the SCR catalyst and the impact of catalyst volume are described. The effect of using an ammonia slip catalyst behind the SCR catalyst is investigated. The durability of the SCR catalyst is described. Finally, examples of the use of computer modelling to refine the optimum volume and urea injection strategy are given. The results demonstrate how a combination of practical experiments and computer modelling can be used to refine the system and provide a cost-effective exhaust aftertreatment solution.