Experimental and Modeling High-Pressure Study of Ammonia-Methane Oxidation in a Flow Reactor.

The present work deals with an experimental and modeling analysis of the oxidation of ammonia-methane mixtures at high pressure (up to 40 bar) in the 550-1250 K temperature range using a quartz tubular reactor and argon as a diluent. The impact of temperature, pressure, oxygen stoichiometry, and CH/NH ratio has been analyzed on the concentrations of NH, NO, NO, NO, N, HCN, CH, CO, and CO obtained as main products of the ammonia-methane mixture oxidation. The main results obtained indicate that increasing either the pressure, CH/NH ratio, or stoichiometry results in a shift of NH and CH conversion to lower temperatures. The effect of pressure is particularly significant in the low range of pressures studied. The main products of ammonia oxidation are N, NO, and NO while NO concentrations are below the detection limit for all of the conditions considered. The NO formation is favored by increasing the CH/NH ratio and stoichiometry. The experimental results are simulated and interpreted in terms of an updated detailed chemical kinetic mechanism, which, in general, is able to describe well the conversion of both NH and CH under almost all of the studied conditions. Nevertheless, some discrepancies are found between the experimental results and model calculations.