Dean, A.M., Johnson, R.L., and Steiner, D.C. (1980)
Shock-Tube Studies of Formaldehyde Oxidation
Combust. Flame 1980, 37, 41.
Abstract
Reflected shock waves were used to heat a variety of formaldehyde mixtures to
temperatures of 1600-3000 K at total concentrations near 5E+18 /cm3. Formaldehyde
decay was monitored by infrared (IR) emission at 3.50 µm using both O2 and
N2O as the oxidant in mixtures highly diluted with argon. Other mixtures with
added CO were monitored for oxygen-atom production via the flame-band emission at
450 nm and for CO2 production via IR emission at 4.27 µm. These data were
then compared to the results obtained from numerical integration of the rate
equations based on a likely mechanism. It was possible to achieve good agreement
with the formaldehyde reaction-rate constants shown below.
The values listed
for k(15) and k(101) are taken directly from the low-temperature studies of these
reactions; the k(-54) and k(58) values also fit recent experiments in this
laboratory on CH2O pyrolysis. The N2O experiments also served as a check on the
rate-constant assignment for the reaction (183). Reasonable agreement was
achieved here. Sensitivity studies suggest these rate constants are probably
accurate to within a factor of 2 at 1700-2500 K. The values of k(15) and k(101)
obtained in this work are at least an order of magnitude lower than the values
frequently used in current modeling studies of methane oxidation. The
implications of these differences are discussed in light of recent suggestions
that C2 species participate in methane oxidation.
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) |
| 15 |
O + CH2O -> OH + HCO |
1.82E+13 |
|
3085 |
1600-3000 |
| -54 |
CH2O + M -> H + HCO + M |
3.31E+16 |
|
81000 |
1600-3000 |
| 58 |
H + CH2O -> HCO + H2 |
3.31E+14 |
|
10500 |
1600-3000 |
| 101 |
OH + CH2O -> HCO + H2O |
7.53E+12 |
|
167 |
1600-3000 |
| 183 |
N2O + H -> N2 + OH |
9.03E+14 |
|
22000 |
1600-3000 |