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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.

Ceramic honeycomb filters performing diesel particulate trapping require regeneration by burning the subsequently accumulated particulate. During this regeneration, thermal failure occurs in some conditions. For developing a highly reliable system with this method, it is necessary to clarify the effects of various factors on the failure to optimize the regeneration conditions. This paper gives the results of an experiment, employing a burner method, of the effect on the damage of regeneration conditions of gas temperature, oxygen concentration, gas flow rate and amount of accumulated particulate, and discusses the regeneration conditions under which the filter is safely operated.

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.