On the Oxidation of Ammonia and Mutual Sensitization of the Oxidation of No and Ammonia: Experimental and Kinetic Modeling

ABSTRACT

The selective non-catalytic reduction of NO by ammonia (SNCR) has been extensively studied but no activation of ammonia oxidation by nitric oxide had been reported. Experiments performed in a jet-stirred reactor (JSR) at atmospheric pressure for various equivalence ratios (0.1–2) and initial concentrations of NH₃ (500 to 1000 ppm) and NO (0 to 1000 ppm) revealed kinetic interactions similar to the so-called mutual sensitization of the oxidation of hydrocarbons and NO. The experiments were performed at fixed residence times of 100 and 200 ms, and variable temperature ranging from 1100 to 1450 K. Kinetic reaction mechanisms were used to simulate these experiments and ammonia oxidation. The most reliable model from the literature was updated (NH₂ + H → NH+H₂, HNO+H → NO+H₂) to better predict ammonia-air burning velocities. It showed the mutual sensitization of the oxidation of ammonia and nitric oxide proceeds through several reaction pathways leading to OH production which is mainly responsible for ammonia oxidation in the current conditions: NH₂ + NO → NNH + OH, NNH → N₂ + H, NNH + O₂ → N₂ + HO₂, H + O₂ → OH + O, H + O₂ + M → HO₂ + M, and NO + HO₂ → NO₂ + OH.

KEYWORDS:

• Ammonia
• kinetics
• modeling
• jet-stirred reactor
• nitric oxide

Acknowledgments

A. Nicolle is gratefully acknowledged for his help with the experiments

Additional information

Funding

Support from the Labex CAPRYSSES (ANR-11-LABX-006-01) is gratefully acknowledged