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As regulations on exhaust gas become stricter, it is desirable that catalytic converters be mounted directly under the engine. Accordingly, in order to improve the reliability of the alumina mat specifications under dynamic load conditions, the compatibility between the vibration conditions and the alumina mat specifications was examined. Through this examination, it was found out that the compatibility could be adjusted by vibration load applied per alumina mat, regardless of the shape of the catalytic carrier. Further, it was found that the fatigue life of the alumina mat complies with that of the ceramic materials.

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.