An experimental, theoretical and kinetic modeling study of the N<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si155.svg" display="inline" id="d1e2468"><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math>O-H<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si155.svg" display="inline" id="d1e2476"><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math> system: Implications for N<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si155.svg" display="inline" id="d1e2484"><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math>O + H
Peter Glarborg, Eva Fabricius-Bjerre, Tor K. Joensen, Hamid Hashemi, Stephen J. Klippenstein
Abstract
The reaction of N 2 O with H is the key step in consumption of nitrous oxide in thermal processes. The major product channel is N 2 + OH, while NH + NO constitute minor products. In addition, a pathway involving HNNO, initiated by N 2 O + H (+M) ⇄ HNNO (+M) (R3, R4), has been inferred from experiment and theory by Burke and coworkers. At longer reaction times, the reaction may reach partial equilibration, and in addition to k 3 and k 4 the importance of this channel depends on the thermodynamic properties of HNNO and its consumption reactions, mainly HNNO + H. In the present work, we re-examined the thermochemistry of HNNO and calculated rate constants and branching fractions for the HNNO + H reaction. Experiments on the N 2 O–H 2 system were conducted in a high-pressure flow reactor at 100 atm as a function of temperature (600-925 K) and stoichiometry and explained in terms of an updated chemical kinetic model. The results support the importance of the HNNO pathway, which results in inhibition of N 2 O consumption and formation of NH 3 . In addition, selected literature results on the N 2 O–H 2 system are re-examined and the implications for the other product channels of N 2 O + H, in particular NH + NO, are discussed. Novelty and significance statement This study provides the first detailed kinetic analysis of the N 2 O/H 2 system at high pressure and intermediate temperatures, based on flow reactor results and high-level theoretical calculations. The experimental conditions augment the importance of a reaction pathway involving HNNO as intermediate. Inclusion in the model of a subset for HNNO, including present calculations for HNNO + H, is crucial for capturing the observed behavior.