An experimental, theoretical and kinetic modeling study of the N2O-H2 system: Implications for N2O+H

The reaction of N2O with His the key step in consumption of nitrous oxide in thermal processes. The major product channel is N2 + OH, while NH + NO constitute minor products. In addition, a pathway involving HNNO, initiated by N2O + 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 k3 and k4 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 N2O-H2 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 N2O consumption and formation of NH3. In addition, selected literature results on the N2O-H2 system are re-examined and the implications for the other product channels of N2O + H, in particular NH + NO, are discussed. Novelty and significance statement This study provides the first detailed kinetic analysis of the N2O/H2 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.