Kinetics in a Lean Formaldehyde Flame

Abstract The structure of a lean formaldehyde-oxygen flame burning at 22.5 Torr has been investigated experimentally using molecular beam sampling coupled with mass spectrometric analysis. Mole fraction profiles have been obtained for stable species as well as for atoms and radicals in a 17.9% CH2O-82.1% O2 flame. From data reduction it appears that about 80% of the formaldehyde is consumed in radical reactions and about 20% by bimolecular decomposition. The fast reactions of formaldehyde with atoms and hydroxyl radicals have the following rate constants: CH 2 +OH→CHO+HO 2 . k 3 =1.8×10 33 exp (−220/T) cm 3 mol −1 s −1 , CH 2 +OH→CHO+OH , xk 4 =6.0×10 13 exp (−1900/T) cm 3 mol −1 s −1 , CH 2 +OH→CHO+H 2 , k 5 =1.0×10 14 exp (−2480/T) cm 3 mol −1 s −1 , Besides these processes, the decomposition reaction of formaldehyde CH 2 +OH→CHO+H 2 +M , k 1 =2.5×10 14 exp (−14,250/T) cm 3 mol −1 s −1 , could play a role in the production of molecular hydrogen in this flame. Formyl radicals disappear mainly by CHO+O 2 +→CO 2 , k 7 =2.7×10 13 exp (−600/T) cm 3 mol −1 s −1 , and this reaction is the principal path for hydroperoxyl radical production. This last species reacts mainly with radicals and atoms (H, O, and OH). In the low temperature zone of the flame, CO2 is produced by CO+OH→CO 2 +H but also to some extent through CO+HO 2 →CO 2 +OH with a rate constant k10 = 3.5 × 1012 exp(−4125/T) cm3 mol−1 s−1

[1]  A. Dean,et al.  Shock Tube Studies of Formaldehyde Oxidation. , 1980 .

[2]  A. A. Westenberg,et al.  Relative rate constants for O + HCO .far. OH + CO and O + HCO .far. H + CO2 , 1972 .

[3]  J. Herron,et al.  Mass spectrometric study of the reactions of atomic oxygen with ethylene and formaldehyde , 1969 .

[4]  H. Niki,et al.  Mass Spectrometric Study of the Reaction of Hydroxyl Radical with Formaldehyde , 1971 .

[5]  Roland H. Smith.  Rate constant and activation energy for the gaseous reaction between hydroxyl and formaldehyde , 1978 .

[6]  R. R. Baldwin,et al.  The inhibition of the hydrogen + oxygen reaction by formaldehyde , 1962 .

[7]  K. Shibuya,et al.  Rate constant measurements for the reactions of oxomethyl radical with nitric oxide and molecular oxygen in the gas phase , 1977 .

[8]  R. Klemm.  Absolute rate parameters for the reactions of formaldehyde with O atoms and H atoms over the temperature range 250–500 K , 1979 .

[9]  A. Lloyd.  Evaluated and estimated kinetic data for phase reactions of the hydroperoxyl radical , 1974 .

[10]  J. Chang,et al.  Reaction rate and products for the reaction oxygen(3P) + formaldehyde , 1979 .

[11]  W. A. Payne,et al.  Rate constant for the reaction of hydroxyl radical with formaldehyde over the temperature range 228-362 K , 1980 .

[12]  H. Niki,et al.  Reaction of Atomic Hydrogen with Formaldehyde , 1965 .

[13]  P. Maker,et al.  Relative rate constants for the reaction of hydroxyl radical with aldehydes , 1978 .

[14]  R. Atkinson,et al.  Kinetics of the reactions of the OH radical with HCHO and CH3CHO over the temperature range 299–426°K , 1978 .

[15]  J. Heicklen,et al.  Reactions of hydroperoxyl radical (HO2) with carbon monoxide and nitric oxide and of oxygen(1D) with water , 1973 .

[16]  B. Veyret,et al.  Absolute rate constants for the reactions of the formyl radical HCO with oxygen and nitric oxide from 298 to 503 K , 1981 .

[17]  P. Tiggelen,et al.  Reaction mechanism and rate constants in lean hydrogen-nitrous oxide flames , 1977 .

[18]  B. Ridley,et al.  Absolute Rate Constant for the Reaction H+H2CO , 1972 .

[19]  Jonathan E. Clark,et al.  HCO production, vibrational relaxation, chemical kinetics, and spectroscopy following laser photolysis of formaldehyde , 1978 .

[20]  H. Niki.  Erratum: Reactions of O(3P) Atoms with Formaldehyde and Diacetylene , 1967 .

[21]  D. D. Drysdale,et al.  Evaluated kinetic data for high temperature reactions , 1972 .

[22]  B. N. Rossiter,et al.  The second limit of hydrogen + carbon monoxide + oxygen mixtures , 1972 .

[23]  G. B. Kistiakowsky,et al.  Pyrolysis and Oxidation of Formaldehyde in Shock Waves , 1965 .

[24]  R. R. Baldwin,et al.  Addition of formaldehyde to slowly reacting hydrogen + oxygen mixtures , 1972 .

[25]  H. Niki.  Reaction of O(3P) Atoms With Formaldehyde , 1966 .

[26]  I. A. Vardanyan,et al.  Kinetics and mechanism of formaldehyde oxidation—II , 1971 .