Secondary Emission Control towards Post China 6 Legislation

Zhao Lei; Jun Zhang; Min Zhou; Carolin Braun; Marcus Schmidt; Joerg Michael Richter; Sonja Batke

doi:10.4271/2021-01-0580

China 6 emission legislation was finalized in 2018 and the full implementation nationwide is postponed to 2021 due to COVID-19. It is foreseen that the post China 6 legislation will have more stringent primary and secondary emission requirements including further reduction of nitrous oxide (N₂O) emissions and likely to include limits on ammonia (NH₃) emissions.

This study investigated the secondary emissions (i.e. N₂O and NH₃) of a variety of China 6 production gasoline vehicles operating under the worldwide harmonized light vehicles test cycle (WLTC) and random test standardized aggressive (RTS 95) cycle. It was found that N₂O emissions were less than 5 mg/km on all these vehicles, far below the current China 6 limit (20 mg/km), however NH₃ emissions varied from 2 to 48 mg/km among the production vehicles.

The mechanisms of N₂O and NH₃ formation and their correlation with primary emissions were also investigated. Methods to reduce N₂O and NH₃ emissions were discussed from the perspective of catalyst system design, including substrate volume, platinum group metals (PGM), and washcoat loading. Finally, a gasoline ammonia slip catalyst (gASC) was proposed and tested on selected vehicles as an add-on device on targeting the reduction of NH₃ emissions. NH₃ emissions were reduced significantly reduced below 5 mg/km on the WLTC.

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Secondary Emission Control towards Post China 6 Legislation 2021-01-0580

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