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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.

Since the monolithic ceramic substrate was introduced for automotive catalytic converters, the reduction of the substrate wall thickness has been a continuing requirement to reduce pressure drop and improve catalytic performance. The thin wall substrate of 0.10 mm (4 mil) thick wall/400 cpsi cell density has been introduced to production by achieving mechanical strength equivalent to a conventional 0.15 mm (6 mil)/400 cpsi substrate. Although a round cross-section substrate can have a reduced catalyst volume compared to an oval cross-section substrate because of uniform gas flow distribution, the smaller cross-section of the round substrate increases pressure drop. The thin wall technology was applied to the round substrate to offset the pressure drop increase and to further improve catalytic performance.

A new alumina mat for a ceramic catalytic converter was developed which is capable of reliably holding a ceramic catalyst carrier up to 900°C. This alumina mat is composed of a fibrous material consisting of 80% by weight of Al2O3 and 20% by weight of SiO2, provides a high surface pressure. The mat has a packing density of 0.2-0.4g/cm3, and can provide not only reliable catalyst holding but also weather resistibility and exhaust gas interception. The mat also has a structural reliability based on the ceramic fatigue theory.