Shock-tube study of CH2O pyrolysis and oxidation

Pyrolysis and oxidation of formaldehyde were studied behind reflected shock waves in the temperature range 1,160-1,890 K at total pressures between 1.4 and 2.5 atm. Formaldehyde decay was followed by using time-resolved IR-laser absorption and IR-emission. The consumption of CH[sub 2]O was promoted by addition of O[sub 2] and the increase in CH[sub 2]O concentration also brought about a promotion of the CH[sub 2]O consumption in the oxidation reaction. A mechanism that can explain the profiles obtained under the experimental conditions was examined by simulation. The present and earlier shock tube data were satisfactorily modeled with a 34-reaction mechanism. The CH[sub 2]O decay rate was very sensitive to the rate constants of the reactions 6, 9, and 25, shown below. Reaction 9 played a very important role in the CH[sub 2]O oxidation under the experimental conditions. New values of the rate constants of these reactions were derived. Reaction 6= CH[sub 2]O + O[sub 2] [r arrow] CHO + HO[sub 2]; Reaction 9= CH[sub 2]O + HO[sub 2] [r arrow] CHO + H[sub 2]O[sub 2]; and Reaction 25= H + HO[sub 2] [r arrow] H[sub 2] + O[sub 2].

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