Experimental study and detailed kinetic modeling of the mutual sensitization of the oxidation of nitric oxide, ethylene, and ethane

New experimental results were obtained for the mutual sensitization of the oxidation of NO and ethane and NO and ethylene in fuel-lean conditions. An atmospheric fused-silica jet-stirred reactor operating over the temperature range 700-1150 K was used. The initial carbon mole fraction was 2500 ppm whereas that of NO varied from 0 to 1200 ppm. Sonic quartz probe sampling followed by on-line Fourier transform infrared analyses and off-line gas chromatography-thermal conductivity detection flame ionization detection analyses were used to measure the concentration profiles of the reactants, stable intermediates, and the final products. A detailed chemical kinetic modeling of the present experiments was performed (147 species, 1085 reversible reactions). An overall good agreement between the present data and modeling was obtained. Furthermore, the proposed model was able to simulate, better than in previous modeling efforts, plug-flow reactor experimental results available in the literature. According to the proposed model, the mutual sensitization of the oxidation of ethane or ethylene and NO proceeds mostly through the conversion of NO to NO2 by HO2 radicals. The NO-to-NO2 conversion is enhanced by the production of HO2 radicals from the oxidation of the fuel. The production of OH resulting from the oxidation of NO by the hydroperoxy radical promotes the oxidation of the fuel: NO + HO2 double right arrow OH + NO2 is followed by OH + C2H4 double right arrow C2H3 + H2O and OH + C2H6 double right arrow C2H5 + H2O. In the case of ethane, at low temperature, the reaction further proceeds via CH3 + O-2 double right arrow CH3O2; CH3O2 + NO double right arrow CH3O + NO2; C2H5O2 + NO double right arrow C2H5O +NO2; C2H5 + O-2 double right arrow C2H4 + HO2. At higher temperature, the sequence is followed by CH3O double right arrow CH2O + H; C2H5O double right arrow CH3CHO + H; C2H5O double right arrow CH3 + CH2O; CH2O + OH double right arrow HCO + H2O; HCO + O-2 double right arrow HO2 + CO; and H + O-2 HO2. In the case of ethylene, the reaction further proceeds via C2H3 + O-2 double right arrow CH2O + HCO; CH2O + OH double right arrow HCO + H2O; HCO + O-2 double right arrow HO2 + CO; and H + O-2 + M double right arrow HO2 + M. The main chemical kinetic differences between the two fuels in presence of NO were analyzed.