Measurements were made for the rate constant of OH + CO + He at 293 K, and OD + CO + M (M = He, Ar, N2, air, SF6) at 253−343 K. Results were also obtained for OH + CO in a shock tube at 1400−2600 K using OH and CO absorption. A two-channel RRKM model of these and other representative results was constructed, with five adjustable parameters. A systematic optimization method was then employed to produce the best fit of the data and provide predictive k(T,P,D/H) expressions for other conditions.

Seven mixtures of formaldehyde and oxygen diluted in argon were studied behind reflected shock waves at temperatures from 1340 to 2270 K and pressures from 0.7 to 2.5 atm. Mixture compositions covered a range from pure pyrolysis to lean oxidation at a stoichiometric ratio of 0.17. The progress of reaction was monitored by laser absorption of CO molecules. Experimental rates of CO formation were found to be 80% higher, in the case of pyrolysis, and 30% lower, under lean oxidation, than those predicted by the current reaction model, GRI-Mech 1.2. The collected experimental data were subjected to extensive detailed chemical kinetics analysis, including optimization with the solution mapping technique. The analysis identified a strong correlation between two rate constants. Assuming a recent literature expression for one of them produced k - 1a = 2.66 × 1024 T -2.57e-215/ T cm6 mol-2 s-1 for the reaction H + HCO + M → CH2O + M. A new expression was developed for the reaction HO2 + CH2O → HCO + H2O2, k 6 = 4.11 × 104 T 2.5e-5136/ T cm3 mol-1 s-1, by fitting the present and literature results. With these modifications, the new reaction model provides good agreement with our experimental data and an acceptable agreement with most literature experimental observations.

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