Validation of a thermal decomposition mechanism of formaldehyde by detection of CH2O and HCO behind shock waves

摘要: The thermal decomposition of formaldehyde was investigated behind shock waves at temperatures between 1675 and 2080 K. Quantitative concentration time profiles formyl radicals were measured by means ofsensitive 174 nm VUV absorption (CH 2 O) 614 FM spectroscopy (HCO), respectively. rate constant the radical forming channel (1a), CH O + M → HCO H M, unimolecular in argon from to K an average total pressure 1 bar, k a = 5.0 x 10 5 exp(-308 k] mol - /RT) cm 3 s . dependence, competing molecular (1b), CH2O CO branching fraction β /(k b ) characterized two-channel RRKM/master equation analysis. With (1b) being main low pressures, found switch (1a) moderate pressures 1-50 bar. Taking advantage results two preceding publications, mechanism with six reactions is recommended. which validated numerous literature experimental observations. capable reliable prediction almost all pyrolysis data, including O, CO, atom measurements 1200-3200 K, mixtures 7 ppm 5% formaldehyde. up 15 Some evidence for self-reaction molecules. At high initial mole fractions reverse reaction (6), OH ⇄ becomes noticeable forward roughly be 6 1.5