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Technical Paper

Hydrocarbon DeNOx Catalysis - System Development for Diesel Passenger Cars and Trucks

1 In recent years Diesel DeNOx catalysts using additional hydrocarbons as reducing agents have been the focus of exhaust aftertreatment. The NOx reduction potential was often limited to 20 - 30 % in the European MVEG-A or the US FTP cycle by just adding a DeNOx catalyst on a vehicle. This result is explained by the fact that the catalyst was treated as a separate item and that the emission reduction strategy was not developed in a system approach. This paper summarizes results regarding the potential of state of the art Diesel DeNOx catalysts fitted to passenger cars and trucks when the exhaust gas system is optimized as a whole. The easiest way for a system approach is the combination of DeNOx catalysts with different working temperatures for NOx reduction. This has been demonstrated by the usage of several base metal catalysts for heavy duty applications. For passenger cars Platinum containing catalysts are strongly favored.
Technical Paper

Development of Oxidation and de-NOx Catalyst for High Temperature Exhaust Diesel Trucks

SOF and de-NOx catalysts are applied to heavy-duty diesel trucks which are regulated by European 13 mode or Japanese 13 mode cycles. Precious metal free catalysts can reduce SOF at low temperatures without increasing sulfates up to 670C. This catalyst shows little deterioration after 400 hours of high temperature engine aging. 32% PM and 47% SOF reduction is observed under 13 mode tests when the exhaust gas temperature exceeds 700C (ECE-13 mode). This precious metal free catalyst is suitable for diesel trucks, especially trucks with natural aspirating engine whose exhaust gas temperature is very high. De-NOx catalysts with a 300-500C NOx reduction temperature window are applied to the Japanese heavy-duty test cycle (Japan 13 mode). When secondary diesel fuel is added under modes 8 to 12, (secondary fuel addition only when catalyst inlet temperature is more than 300C), 19-25% NOx can be reduced with 2-4% fuel penalty.