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In order to meet the strict automobile emission regulations in the U.S.A. and Europe, new aftertreatment technologies such as the EHC and HC Adsorber have been developed to reduce the cold start emissions. The EHC is obviously effective in reducing emissions, but has the demerits of a large electric power demand and a complicated power control system to support it (13). A by-pass type HC adsorber system has the concerns of unreliable by-pass valves and complicated plumbing (10). A major technical challenge of the in-line type HC adsorber was the difference between the HC desorption temperature and the light-off temperature of the burn-off catalyst. This paper describes the evaluation results of a completely passive “In-line HC Adsorber System” which can reduce the cold start emissions without the application of any type of mechanical or pneumatic control valve in the exhaust system.

The in-line hydrocarbon(HC) adsorber is one type of passive after-treatment technology which can reduce the cold start hydrocarbon from automobile engine exhaust gas. However, major technical issues to be resolved for practical use of this system are 1)the temperature difference between HC desorption from the adsorbent and activation of the catalyst to burn-off the desorbed HCs and 2)the ability to adsorb a wide range of HC molecule sizes in the cold exhaust gas. Recent zeolite development has resulted in an unique adsorbent capable of adsorbing small HC molecules as well as large to some degree, even under aqueous conditions. This adsorbent also features a relatively high HC desorption temperature. As a result, an In-line HC adsorber system has been developed, which can trap more unburned HCs during the engine cold start phase and burn-off the desorbed HCs more efficiently in the desorption phase by using this unique adsorbent.