N2O Consumption by Thermal Decomposition and Reduction with CH4, C2H6 and NH3

Abstract

ABSTRACTConsumption of nitrous oxide (N2O) by thermal decomposition and reduction with methane (CH4), ethane (C2H6), and ammonia (NH3) were investigated using a micro-flow reactor with controlled temperature profile. N2O mole fractions were measured using a gas chromatograph and mass spectrometers at the maximum wall temperatures from 900 to 1400 K. For N2O thermal decomposition, the measured N2O mole fraction was in good agreement with the prediction using the model proposed by Mulvihill, et al. The low-pressure limit of N2O (+M) = N2 + O (+M) was dominant and H2O showed the largest impact on N2O consumption as a third-body, followed by CO2 and Ar. New third-body coefficients were proposed from the comparison of measured N2O mole fractions with model predictions. For N2O reduction with respective fuels, experiments showed that N2O consumption became greater in the order of C2H6/N2O/Ar ≈ NH3/N2O/Ar > CH4/N2O/Ar > N2O/Ar mixtures. Chemical reaction analyses showed that N2O + H = N2 + OH is the dominant reaction for N2O consumption in all fuel/N2O cases. In the C2H6/N2O case, high rates of H radical production from the fuel radical (C2H5) at a low temperature was identified, resulting in a greater N2O consumption than the CH4/N2O case. In the NH3/N2O case, a reaction of N2O and the fuel radical (NH2) showed high contribution to N2O consumption. Additionally, NNH and H2, the products in N2H2 + H = NNH + H2, produce H radicals through subsequent reactions. These reactions create a cycle of production/consumption of H and OH radicals and promote consumption of NH3 and N2O.