Hochgreb, S., and Dryer, F.L. (1992)
A Comprehensive Study on CH2O Oxidation Kinetics
Combust. Flame 1992, 91, 257.
Abstract
Results of calculations based on detailed chemical mechanism for the oxidation of formaldehyde are compared with data from a variety of experimental conditions: flow reactor, shock tube, static reactor, and a lean flame. The range of conditions spans temperatures from 773 to 2500 K, equivalence ratios from pure pyrolysis to very fuel-lean and pressures from 0.3 to 1.5 atm. New experimental results from the oxidation of formaldehyde in flow reactors at 1095 K are reported. The original model, based on reaction rate constants obtained in the literature, was modified based on comparisons of calculated and experimental results. Recommended changes were guided by extensive sensitivity and flux analysis for each case, as well as on the current knowledge of uncertainties in reaction rate constant values. The comprehensive mechanistic features of formaldehyde oxidation at low and high temperatures are discussed. The results of the analysis reveal the key role of HO2 radicals up to temperatures around 1100 K, through the cycle (168), (121) and (-85). Shock tube data are revisited using more recent reaction rate constants to verify the model. Finally, the competition between formyl radical reactions (167) and (168), which determines the rate of production of H radicals, was found to be primary controlling factor in the evolution of lean formaldehyde flames. A matrix of influences of the most important reaction rates on the calculated parameters for the different experimental conditions summarizes the conclusions.

REACTION RATE COEFFICIENTS SUGGESTED IN THIS WORK:

GRI-Mech
Number
('-' sign
means
reverse)		 Reaction Rate Coefficient
A T^n exp(-E/RT)		 Temperature
Range
(K)
A
(mol,cm3,s)		 n
(T in K)		 E
(cal/mol)
-54 CH2O + M -> H + HCO + M 4.21E+23 -1.66 92170 700-2500
58 H + CH2O -> HCO + H2 5.18E+7 1.66 1834 700-2500
121 HO2 + CH2O -> HCO + H2O2 1.47E+13   15200 700-2000