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A completely passive cold-start emissions control system, without any secondary air source, was developed to reduce cold start hydrocarbon (HC) emissions. The Air-Less Adsorber (ALA) system has a first catalyst, an adsorber, and a second catalyst. The system is designed to adsorb a large fraction of hydrocarbons (HC) during cold start, followed by optimized heating of the second catalyst before adsorber HC desorption. During the HC desorption cycle, the engine is running in closed-loop control near stochiometric air/fuel ratio. There is enough oxygen to oxidize the desorbed HC over the second catalyst. The ALA system was evaluated using the FTP test on a 3.8 liter V6 vehicle. The ALA system reduced up to 38% of cold start HC emissions beyond the catalyst-only baseline. The system is truly passive.

An In-line hydrocarbon (HC) adsorber system was developed to reduce cold start HC emissions. The system comprises a first catalyst, adsorber unit, and a second catalyst for oxidation of desorbed HC. During cold start, exhaust gas is directed to the hydrocarbon adsorber using a fluidic flow diverter unit without any mechanical moving parts in the exhaust system. After the first catalyst lights off, the diverter is shut off and the major portion of the exhaust gas then flows directly to the second catalyst without heating the adsorber unit. After the second catalyst reaches light-off temperature additional air was added to oxidize the desorbed HC. The system attributes: NMHC emissions in ULEV range Straight line axial flow Reliable design Limited back pressure penalty The system was tested on a 3.8L U.S. vehicle.

A by-pass zeolite adsorber system consisting of a first catalyst, a by-pass loop containing the zeolite adsorbers followed by a downstream second catalyst was FTP tested using a U.S. vehicle equipped with a 3.8 L, V6 engine. The system exhibited ULEV emissions performance with hydrocarbon adsorption and regeneration (desorption and oxidation) within the FTP cycle and required only a single diversion valve within the exhaust line. Adsorption takes place during the initial 70 seconds of the FTP cycle. The adsorbers were regenerated with the exhaust gas plus injected air.