Experimental and detailed kinetic modeling study of the high pressure oxidation of methanol sensitized by nitric oxide and nitrogen dioxide

摘要

The perturbation of the combustion by NO_x is important in several practical systems (recent NO_x-re-duction strategies, combustion with exhaust-gas recirculation in diesel and HCCI engines and for mild combustion). New experimental results were obtained for the oxidation of methanol in absence and in presence of NO or NO_2 in a fused silica jet-stirred reactor operating at 10 atm, over the temperature range 700-1100 K. Probe sampling followed by on-line FTIR analyses and off-line GC-TCD/FID analyses permitted 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. An overall good agreement between the present data and this modeling was obtained. The oxidation of methanol is significantly sensitized by NO_2, whereas the effect of NO is more limited. According to the proposed model, the mutual sensitization of the oxidation of methanol and NO proceeds through the NO to NO_2 conversion by HO_2. The increased production of OH resulting from the oxidation of NO by HO_2 promotes the oxidation of the fuel. A simplified reaction scheme can be proposed for the NO-seeded oxidation of methanol: NO + HO_2 => NO_2 + OH followed by OH + CH_3OH => H_2O + CH_2OH and CH_3O. The enhanced oxidation of methanol by addition of NO_2 is also due to additional OH production through: NO_2 + HO_2 => HONO + O_2, NO_2 + H => NO + OH and HONO => NO + OH followed by OH + CH3OH => CH2OH and CH3O. The further reactions CH_2OH + O_2 => CH_2O + HO_2; CH_3O => CH_2O + H; CH_2O + OH => HCO; HCO + O_2 => HO_2 and H + O_2 => HO_2 complete the sequence whether NO or NO_2 is added.