Adsorption and Desorption Characteristics of the Adsorber to Control the HC Emission from a Gasoline Engine

Three-way catalyst systems for gasoline engines do not activate under engine cold start conditions since exhaust gas temperature is low. Zeolite based hydrocarbon (HC) adsorber substrate stores high-concentration HC emitted immediately after engine start and oxidizes when HC is released as the exhaust gas temperature rises. This report describes about the results obtained by the laboratory test and the engine vehicle experiments relating the adsorption and desorption characteristics of HC adsorption. The influences of the silica alumina ratio (Si/2Al ratio) of the zeolite and water vapor (H₂O) to HC adsorber, and the difference of adsorption mechanism between propylene (C₃H₆) and toluene (C₇H₈) were investigated also. The results obtained by engine experiments showed good coincidence with the obserbation by the model gas laboratory test.