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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.

Ceramic preconverters have become a viable strategy to meet the California LEV and ULEV standards. To minimize cold start emissions the preconverter must light-off quickly and be catalytically efficient. In addition, it must also survive the more severe thermomechanical requirements posed by its close proximity to the engine. The viability of the ceramic preconverter system to meet both emissions and durability requirements has also been reported recently(1,2). This paper further investigates the impact preconverter design parameters such as cell density, composition, volume, and catalyst technology have on emissions and pressure drop. In addition, different preconverter/main converter configurations in conjunction with electrically heated catalyst systems are evaluated. The results demonstrate that ceramic preconverters substantially reduce cold start emissions. Their effectiveness depends on preconverter design and volume, catalyst technology, and the system configuration.

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 new adsorber concept has been tested. A zeolite adsorber with a central hole is mounted below the first catalyst, with a second catalyst downstream. During the cold start, when the adsorber is cool and the HC concentration high, HCs are adsorbed from the gas fraction passing through the channels. The small fraction of exhaust gas passing through the hole impinges directly on and heats the second catalyst. The rationale is to design the hole to maximize the second catalyst heating rate, minimize desorption during heat-up and simultaneously keep the HCs which pass through the hole at an acceptably low level. FTP test results on the 3.8 L engine give 0.081 g/mi NMHC with no hole (same as base line) and decrease to 0.056 g/mi NMHC with the hole. This concept exhibits NMHC performance in the LEV range.

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.