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With ever more stringent CO2 emissions mandates, many automobile manufacturers are seeking the fuel economy benefits of diesel and lean-burn gasoline engines. At the same time the emissions standards that diesel and gasoline engines will have to meet in the next decade continue to reduce. Proposed solutions for meeting the stringent emissions standards all appear to have limitations, such as propensities to poisoning from sulfur, narrow operating temperature windows, and requirements for controls that give rapid rich excursions. Non-thermal plasma-catalyst systems have shown good performance in bench testing while being largely unaffected by these same issues. A two-stage system with a unique non-thermal plasma reactor combined with a zeolite-based catalyst has been constructed and shown to work over a wide temperature range.

A real world aging study was performed on a distributed converter system to investigate ULEV potential and aging aspects. Two V-6 vehicles were fitted with 0.7 Liter Pd close mounted catalysts on each exhaust manifold and a traditional 2.8 Liter three-way underfloor catalyst. These vehicles were then driven in a high mileage fleet while tracking emission results every 10K miles up to 50K miles. At the end of 50K miles the system met ULEV requirements for CO and NOx but NMHC exceeded the target. Verification of aging was done by chemically cleaning the close coupled catalyst and by comparison to a dynamometer aged set. The results showed that most of the degradation in NMHC performance was due to poisoning with little effect from thermal aging. With most of the CO and NOx abatement being done in the underfloor catalyst their degradation is mainly thermal.