Laser probing and kinetic modeling of no and co production in shock-wave decomposition of nitromethane under highly diluted conditions

The decomposition of nitromethane (CH 3 NO 2) in a shock tube has been studied by using a frequency-stabilized CW CO laser to measure the real-time production of NO and CO, two of the key decomposition products. Highly diluted CH 3 NO 2 /Ar mixtures (0·15 -0·75% CH 3 NO 2) were used in incident shock experiments over the temperature range from 940 to 1520K and pressure range from 0·4 to 1·0 atm. A mechanism consisting of 37 chemical reactions was used to model the formation of these two products over the entire range of experimental conditions employed. All but one rate constant (i.e. CH 3 + CH 2 O) were obtained either from the literature or from simple TST and RRKM calculations. The NO profiles could be quantitatively modeled over the entire temperature range, whereas those of CO could be accounted for only by increasing the values of the rate constant for CH >3 + CH 2 O determined at low temperatures by more than a factor of 30. The reason for this adjustment is discussed. The combination of the evaluated rate constants with others for the CH 3 + CH 2 O reaction covering the range of 350–1500K gave rise to the expression: Additionally, strong oscillatory behavior in the NO and CO profiles was observed when 2·5 – 3·0% CH 3 NO 2 mixtures were shock-dissociated. A similar behavior was not detected in CH 3 ONO decomposition under the same conditions. The comparison of these two isomeric systems will be made.