The combustion of gaseous aldehydes studied by flash photolysis and kinetic spectroscopy

1960 ◽  
Vol 254 (1277) ◽  
pp. 147-162 ◽  
Keyword(s):  
Free Radicals ◽  
Formic Acid ◽  
High Temperatures ◽  
Flash Photolysis ◽  
Kinetic Mechanism ◽  
Kinetic Spectroscopy ◽  
Elementary Reactions ◽  
Slow Reaction ◽  
Explosive Reaction ◽  
Explosive Combustion

The identity and behaviour of free radicals produced during the combustion of gaseous aldehydes has been examined. The flash-initiated combustion of formaldehyde was investigated under conditions of slow and explosive combustion. The behaviour of formaldehyde and the derived radicals OH and HCO was followed during the course of the reaction. It was found that HCO radicals react rapidly with oxygen during the slow reaction, but decompose into H atoms and CO at the high temperatures produced during the explosive reaction. Further information on the reaction between HCO radicals and oxygen was obtained by flash - photolyzing gaseous formic acid in presence of oxygen and nitrogen under isothermal conditions. The results of this investigation are consistent with the kinetic observations previously made by Axford & Norrish. With one modification relating to the participation of HCO radicals they confirm the kinetic mechanism previously deduced by these authors. The flash-initiated combustion of acetaldehyde was also investigated under conditions of slow and explosive combustion, and information on several of the elementary reactions proceeding under these conditions has been obtained.

The combustion of gaseous methyl iodide studied by flash photolysis and kinetic spectroscopy

1961 ◽  
Vol 263 (1312) ◽  
pp. 51-57 ◽  
Keyword(s):  
Free Radicals ◽  
Gas Phase ◽  
Methyl Iodide ◽  
Flash Photolysis ◽  
Oh Radicals ◽  
Methyl Radicals ◽  
Kinetic Spectroscopy ◽  
Slow Combustion ◽  
Low Pressures ◽  
Explosive Combustion

The combustion of gaseous methyl iodide has been studied under conditions of slow and explosive combustion and the behaviour of the methyl iodide, the free radicals OH and IO and the products formaldehyde and iodine has been followed by kinetic spectroscopy. At fairly low pressures ( l.0 to 5.5 cm Hg) the behaviour of the methyl iodide and the OH radicals under conditions of slow and explosive combustion indicates that the reaction between methyl radicals and oxygen proceeds by CH 3 + O 2 → H 2 CO + OH. At higher pressures, under slow combustion conditions, formaldehyde is detectable in the gas phase by reaction between methyl radicals and oxygen. Under slow combustion condi­tions also, the behaviour of the IO radicals and iodine suggests that the iodine atoms produced by the primary photolytic dissociation of m ethyl iodide are temporarily removed in the form of IO radicals, from which the final product iodine is then formed by 2IO → I 2 + O 2 .

Studies of the explosive combustion of hydrocarbons by kinetic spectroscopy I. Free radical absorption spectra in acetylene combustion

1953 ◽  
Vol 216 (1125) ◽  
pp. 165-183 ◽  
Keyword(s):  
Absorption Spectra ◽  
Total Pressure ◽  
Flash Photolysis ◽  
Initial Period ◽  
Kinetic Spectroscopy ◽  
Radical Concentration ◽  
Stage 4 ◽  
Explosive Reaction ◽  
Stage 1 ◽  
Flash Spectroscopy

The explosive oxidation of acetylene, initiated homogeneously by the flash photolysis of a small quantity of nitrogen dioxide, has been investigated by flash spectroscopy. The absorption spectra of OH, CH, C 2 (singlet and triplet), C 3 , CN and NH, a number of which have not previously been observed, are described, and the relative concentrations, at all times throughout the explosion, are given. Four stages have been distinguished in the explosive reaction: 1. An initial period during which only OH appears. 2. A rapid chain branching involving all the diatomic radicals. 3. Further reaction, occurring only when oxygen is present in excess of equimolecular proportions, during which the OH concentration rises exponentially and the other radicals are totally consumed. 4. A relatively slow exponential decay of the excess radical concentration remaining after completion of stages 2 and 3. The duration of stage 1 is 0 to 3 ms. In an equimolecular mixture at 20 mm total pressure, containing 1.5 mm NO 2 , the durations of both stage 2 and stage 3 are approximately 10 -4 s and the half-life of OH in stage 4 is 0.28 ms. A preliminary interpretation of these changes and of the radical reactions is given.

Flash-photolysis electron spin resonance in solution studies of free radicals

1984 ◽  
Vol 78 ◽  
pp. 257 ◽  
Author(s):  
Christopher D. Buckley ◽  
Andrew I. Grant ◽  
Keith A. McLauchlan ◽  
Andrew J. D. Ritchie
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Flash Photolysis ◽  
Solution Studies ◽  
Spin Resonance

Laser flash photolysis studies of elementary reactions of significance in combustion

1990 ◽  
Vol 46 (4) ◽  
pp. 581-588 ◽  
Author(s):  
J.W. Davies ◽  
M.A. Hanning-Lee ◽  
M.J. Pilling ◽  
P.W. Seakins
Keyword(s):  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Elementary Reactions

The Reaction of S(3P) Atoms with Molecular Oxygen

1971 ◽  
Vol 49 (10) ◽  
pp. 1659-1664 ◽  
Author(s):  
R. W. Fair ◽  
A. Van Roodselaar ◽  
O. P. Strausz
Keyword(s):  
Molecular Oxygen ◽  
Rate Constant ◽  
Ground State ◽  
Vacuum Ultraviolet ◽  
Flash Photolysis ◽  
Ultraviolet Region ◽  
Kinetic Spectroscopy ◽  
Vacuum Ultraviolet Region

The rate constant of the reaction of ground state S(3P) atoms with molecular oxygen, S(3P) + O2(X3Σg−) → SO(X3Σ−) + O(3P), has been determined as (1.7 ± 0.2) × 1012 cm3 mol−s− at 298 °K by means of kinetic spectroscopy in the vacuum ultraviolet region. The source of S(3P) atoms was the isothermal flash photolysis of COS in the presence of Ar or CO2.

Theoretical Investigation of Autoignition of Combustible Gas Mixtures in Rapid Compression Machines

2002 ◽  
Author(s):  
Shaoping Shi ◽  
Daniel Lee ◽  
Sandra McSurdy ◽  
Michael McMillian ◽  
Steven Richardson ◽  
...  
Keyword(s):  
Experimental Data ◽  
Theoretical Investigation ◽  
Ignition Delay ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Reaction Scheme ◽  
Independent Manner ◽  
Elementary Reactions ◽  
Chemical Kinetic Mechanism ◽  
Rapid Compression

In any theoretical investigation of ignition processes in natural gas reciprocating engines, physical and chemical mechanisms must be adequately modeled and validated in an independent manner. The Rapid Compression Machine (RCM) has been used in the past as a tool to validate both autoignition models as well as turbulent mixing effects. In this study, two experimental cases were examined. In the first experimental case, the experimental measurements of Lee and Hochgreb (1998a) were chosen to validate the simulation results. In their experiments, hydrogen/oxygen/argon mixtures were used as reactants. In the simulations, a reduced chemical kinetic mechanism consisting of 10 species and 19 elementary reactions coupled to a CFD software, Fluent 6, was used to simulate the autoignition. The ignition delay from the simulation agreed very well with that from the experimental data of Lee and Hochgreb, (1998b). In the second case, experimental data derived from an RCM with two opposed, pneumatically driven pistons (Brett et al., 2001) were used to study the autoignition of methane/oxygen/argon mixtures. The reduced chemical kinetic mechanism DRM22, derived from the GRI-Mech reaction scheme coupled to Fluent 6, was applied in the simulations. The DRM22 scheme included 22 species and 104 reactions. When methane/oxygen/argon mixture were simulated for the RCM, the ignition delay deviated about 15% from the experimental results. The simulation approaches as well as the validation results are discussed in detail in this paper. The paper also discusses an evaluation of reduced reaction models available in the literature for subsequent Fluent modeling.

Thiophosphonyl Radicals Photolytic Generation and Reactivity Towards Olefinic Compounds

1985 ◽  
Vol 40 (6) ◽  
pp. 541-543 ◽  
Author(s):  
T. Sumiyoshi ◽  
W. Weber ◽  
W. Schnabel
Keyword(s):  
Absorption Spectrum ◽  
Free Radicals ◽  
Optical Absorption ◽  
Vinyl Acetate ◽  
Optical Absorption Spectrum ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Uv Light ◽  
Strong Band

Upon irradiation with UV light (λ = 347 nm), 2,4,6-trimethylbenzoyldiphenylphosphine sulfide was found to be fragmented into free radicals by α-scission (F(k) = 0.3 ± 0.1): Flash photolysis studies revealed that the optical absorption spectrum of diphenylthiophosphonyl radicals, S = P(Ph)2. possesses a strong band with λmax = 340 nm and a somewhat weaker band with λmax ≈ 500 nm (e340nm = 1.2 ± 0.2) · 104 1/mol cm). The reactivity towards olefinic compounds, M, is 10 to 30 times lower than in the case of O = P(Ph)2 radicals. Typical bimolecular rate constants (in 1/mol s) of the reaction of S = P(Ph)2 with M are: 4 x 106 (styrene), 6.2 x 105 (methylacrylate), 4.2 x 104 (vinyl acetate).

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