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Two effects of rich-spike duration on NOx-storing have been analyzed. The first one, that NOx-storing speed decreases as rich-spike duration increases, is explained as the influence of NOx diffusion in wash-coat layer, which is quantified by a simple mathematical expression for NOx-storing rate. The second one, a peculiar behavior of NOx-storing in appearance of the outlet NOx concentration, is clarified: Heat produced directly or indirectly (via oxygen storage in ceria) by rich-spike warms up the downstream part, which releases excess NOx at the raised temperature. Contributions of the oxygen storage and the carbonate of NOx-storage material are also discussed.

Transient temperature and concentration distribution inside a catalytic converter during warm-up have been analyzed by experiments and numerical simulation. There is great maldistribution of species concentrations inside a converter during warm-up. Carbon monoxide (CO) and hydrocarbons (HC) have high concentrations in the exhaust gas passing through outer region cells because they are not converted due to low wall temperature. The effects of the noble metal loading pattern on conversion characteristics during warm-up have been investigated by numerical simulation. The effects of high-loading on improving conversion characteristics are saturated with the loading quantity of six times that of the base-loading. High-loading of the noble metal only on the frontal region (20 or 30mm. from the front face) has almost the same warming-up conversion performance as the uniform high-loading.

This paper presents the numerical simulation method to predict the deactivation process of three-way catalytic converters. Three-way catalytic converter's deactivation typically results from thermal and chemical mechanisms. The major factor of thermal deactivation is the sintering of noble metal particles, which is known to depend on the ageing temperature and the oxygen concentration in the exhaust gas. The chemical deactivation is mainly caused by the poisoning, which has two effects on the catalyst deactivation. One effect is the loss of the catalyst activity, which is expressed by reduced frequency factors of reaction rates. Another effect is the suppression of the noble metal sintering. Poison deposits prevent the noble metal particles from moving in the washcoat, assisted by the reduced thermal loading of reaction heats, which is caused by the loss of the catalyst activity. Modeling these deactivation factors, we propose the rate expression of noble metal sintering.