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The new concept catalyst for diesel engine has been developed. When the exhaust temperature is low, SOF and HC are temporarily adsorbed by the adsorbent within the catalyst and are oxidized as the temperature rise. This is a different that the low-temperature oxidation activity is appeared by the noble metal loading of the catalyst. The process of this development have manifested as follows. 1. The coating material is important factor to govern the oxidation activity. 2. SOF is reduced by the coating material in low temperature less than 200 3. The coating material, which has low SO2 adsorbing rate suppress the sulfate formation at high temperature. 4. To reduce NOx in the diesel engine exhaust gas is possibility by utilizing adsorptive characteristics of the catalyst.

A new 3-way catalyst with NOx conversion performance for lean-burn engines has been developed. The catalyst oxidizes NOx and stores the resulting nitrate, which is then reduced by HC and CO during engine operation around the stoichiometric air/fuel ratio. Both the composition of the storage component and the particle sizes of the noble metal were optimized. In addition, a special air fuel mixture control has been developed to make the best of the NOx storage-reduction function. The present catalyst showed 90% conversion efficiency and improved fuel economy by 4% in the Japanese 10-15 mode test cycle. The efficiency remained at 60% or more after durability test.