Abstract
• The inlet temperature played an important role in the formation of N 2 O and NH 3. • The maximum N 2 O concentration and NH 3 formation raised with the increase of H 2 O content. • The formation of N 2 O decreased with the increase of CH 4 concentration, which was contrary for NH 3 . • The emission of N 2 O and NH 3 decreased to zero by controlling the exhaust gas temperature and O 2 concentration. To investigate the effects of inlet temperature and exhaust gas composition on the formation characteristics of nitrous oxide (N 2 O) and ammonia (NH 3 ) for stoichiometric natural gas engines with Pd-only three-way-catalyst (TWC) , a global model of Pd-only TWC by constructing a comprehensive catalytic reaction mechanism was established and a simulation investigation of the effect of inlet temperature, H 2 O content, oxygen (O 2 ) concentration and methane (CH 4 ) concentration on the formation of N 2 O and NH 3 was conducted. The results showed that the inlet temperature played an important role in the formation of N 2 O and NH 3. N 2 O was easy to generate N 2 through secondary reduction under high temperatures·NH 3 was formed by the reduction of nitric oxide (NO) through hydrogen (H 2 ). The H 2 required for the reduction came from the reactions of steam reforming and water gas shift on the Pd surface. The formation of NH 3 by the reduction of NO through H 2 at a temperature above 750 K. Secondly, the maximum N 2 O concentration and NH 3 formation raised with the increase of H 2 O content. In addition, the emission of N 2 O and NH 3 decreased to zero by controlling the exhaust gas temperature and O 2 concentration. Finally, the formation of N 2 O decreased with the increase of CH 4 concentration, which was contrary to NH 3 . The emission of N 2 O and NH 3 declined to zero by controlling the exhaust gas temperature in the range of 700 K–750 K under 1500 × 10 −6 CH 4 .
Published Version
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