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In order to meet recent and future stringent hydrocarbon emission regulations of passenger cars, the use of Pd-containing catalysts is of growing interest. This is especially true for Pd/Rh and Pt/Pd/Rh catalysts. To optimize the function of the individual precious metals, most high-performance catalysts have a double layer configuration. This double layer avoids undesired interactions between Pd and Rh after reacting with exhaust gas at a high temperature level. Of course, these double layer technologies lead to a more complex capacity utilization coating process during the manufacture of the catalyst. The present work summarizes the results of a research program targeting the development of a high-performance single layer Pd/Rh catalyst technology. The starting point was the functional improvement of Pd and Rh only catalysts then subsequently combining the best of these technologies.

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.