Showing papers on "Elementary reaction published in 1971"

A Theoretical Analysis of Premixed Flame Propagation with an Isothermal Chain Reaction.

Abstract: : An asymptotic analysis, for large activation energies, is presented of the structure of a deflagration wave supported by a two step chemical reaction mechanism with a first order chain-branching reaction and a second order chain termination reaction. In the first step the initial reactant is transformed, without liberation of heat, into an intermediate species; the reaction is auto-catalytic and has a large activation energy. In the second step the intermediate species recombines, with liberation of heat, to give the final products. Three main regimes are found in the analysis. For low recombination rates, an isothermal chain reaction flame precedes a much thicker recombination region where transport effects may be neglected. (Author)

The use of the H2+O2 reaction in determining the velocity constants of elementary reaction in hydrocarbon oxidation

Abstract: Traces of C 2 H 6 , C 3 H 8 , n - and iso -C 4 H 10 have been added to slowly reacting mixtures of H 2 +O 2 in aged boric-acid-coated reaction vessels at 480°C. From measurements of the relative loss of H 2 and RH, velocity constants for reactions of the radicals H and OH with RH have been determined. Combination with independent data has enabled over-all Arrhenius parameters to be obtained for these reactions. Arrhenius parameters have also been obtained for specific attack at primary, secondary, and tertiary C-H bonds in the hydrocarbons by assuming that all C-H bonds of a particular type are identical in these hydrocarbons. Product analyses have been carried out over a wide range of mixture composition and reactions of the organic radical, formed from the additive, have been investigated. The major products from C 2 H 6 , C 3 H 8 , n - and iso -C 4 H 10 are the conjugate olefines, and estimates of the over-all velocity constants for the olefin-forming reactions lie in the range 10 7 to 10 8 liter mole −1 sec −1 at 480°C. The over-all velocity constants for the reactions of alkyl radicals with O 2 to give aldehydes and epoxides range from 10 5 to 10 6 liter mole −1 sec −1 . With neopentane, the main primary products are 3,3-dimethyloxetane, CH 3 COCH 3 , (CH 3 ) 2 C=CH 2 , HCHO, and CH 4 . The marked increase in the yield of CH 3 COCH 3 with increasing pressure of O 2 has been explained in terms of the formation of the (CH 3 ) 2 CCH 2 -(OOH)CH 2 OO radical.

Shock-tube study of high-temperature pyrolysis of benzene

Abstract: High-temperature pyrolysis of benzene was studied by the shock-tube method. Single-pulse experiments were carried out at 1400°–1900°K, 2–8 atm total pressure (benzene was diluted to 10%–20% with argon) and with a reaction time of about 400 μsec. From the experimental results it was found that the pyrolysis reaction of benzene was second order with respect to the benzene concentration and the rate constant was k = 10 9.5 exp ⁡ ( − 30 ± 5 kcal / RT ) liter mole − 1 sec ⁡ − 1 . It was also found that the pyrolysis reaction was slowed down considerably by the addition of hydrogen and promoted by the addition of methane Absorption spectro-photoelectronic experiments were carried out under almost the same conditions as the single-pulse experiments. There were two absorption maxima in the wave-length range from 3000 to 6500 . Monochromatric experiments at 3000 and 6500,showed induction periods for the appearance, the peak, and the decay of absorption in oscillograms. A new scheme for the chain mechanism, involving several elementary reactions, was developed and compared with the experimental results.

The reaction of p-substituted nitrosobenzenes with N-alkyl-N-arylhydroxylamines

Abstract: The reaction between N-benzyl-N-phenylhydroxylamine and para-substituted nitrosobenzenes has been investigated and the products have been identified. Kinetic studies show that the reaction is bimolecular in the early stages and that this initial rate is profoundly influenced by the nature of the para-substituent. A reaction mechanism involving an initial electron-transfer step within a cyclic assembly is proposed.

Effect of dose rate on the radiation-induced polymerization of ethylene in tert-butyl alcohol

Abstract: The effects of pressure of the radiation-induced polymerization of ethylene in tert-butyl alcohol were studied. The reaction was carried out by use of a reactor with a capacity of 100 ml under the following conditions; pressure, 60–400 kg/cm2; temperature, 24 ± 3°C; dose rate, 2.0 × 104−1.6 × 105 rad/hr; amount of medium (tert-butyl alcohol containing 5 vol-% water), 70 ml. The results of polymerization were analyzed by a kinetical treatment based on a reaction mechanism with both first- and second-order terminations for the concentration of propagating, radical. On the basis of the kinetical treatment the rate constants of each elementary reaction at several pressures were determined, and the activation volumes of elementary reactions were obtained and are discussed in connection with the reaction mechanism. Consequently, the rate constants of propagation, first-order termination, and second-order termination at pressure p and at 24°C were expressed by,

On the Distinction between Reaction Fluxes and Phenomenological Rate Constant

Abstract: The physical interpretation of the phenomenological rate constants of chemical kinetics is examined. For perfect gas systems, the traditional view of the rate constants for elementary reactions as ...

Thermal decomposition of chloropicrin

Abstract: 1. The decomposition rate of chloropicrin in the gas phase (50-400 torr) depends on the pressure and the added inhibitors. 2. The rate constant of the elementary reaction of trichloronitromethane was determined.

Determination of the elementary reaction rate constants on the basis of the summary values of the rate constants

Abstract: The rate constants of reactions of atomic oxygen with methane, ethane, ethylene, and propylene along different pathways were determined on the basis of the ratios between the concentrations of the products formed and the summary rate constants measured earlier.

Laboratory Studies of Elementary Reactions of Neutral Species Containing O or H

Abstract: Much information about the reactions of ground state oxygen, hydrogen and nitrogen atoms, of simple radicals such as OH, HO2 and of metastable molecules such as O 2 (1Δg) and comes from the study of reactions in discharge-flow systems (Kaufman, 1961; Campbell and Thrush, 1965). In this type of apparatus free atoms are produced by passing the parent molecules through an electrodeless radio-frequency or microwave discharge; typically total pressures between 0.1 Torr and 10 Torr are used to minimise difficulties associated with diffusional effects or pressure drop and the concentrations of active species are usually ca. 1 % of the total flow. Reactions can be studied at temperatures from 1000 K down to 200 K or below, provided that no species is condensed on the flow tube wall and that the reaction proceeds at a measurable rate.