Topic
Elementary reaction
About: Elementary reaction is a research topic. Over the lifetime, 2972 publications have been published within this topic receiving 76110 citations.
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01 Feb 1985
TL;DR: In this article, the authors used atomic resonance absorption spectrometry (ARAS) to record simultaneously H and O-atom concentration profiles in the post-shock region behind reflected shocks.
Abstract: Shock heating together with atomic resonance absorption spectrometry (ARAS) was used to record simultaneously H- and O-atom concentration profiles in the post-shock region behind reflected shocks. The dissociation of N2O together with the reaction O + H2 = OH + H was used as a source of H and OH for the reactions H + O2 = OH + O and OH + H2 = H2O + H. The test gas mixtures consisted of argon with relative concentrations of a few ppm N2O and 100 to 500 ppm H2 and O2. The experiments were conducted in the temperature range of 1700 to 2500 K at total densities of 6 · 10−6 to 1.3 · 10−5 mol cm−3. The following rate coefficients were deduced:
For temperatures below 2500 K nearly complete agreement with the value for the rate coefficient of reaction R1 as recommended by Baulch [1] was obtained. For reaction R2 a rate coefficient was deduced which is close to the value as given by Gardiner et al. [23].
105 citations
01 Nov 1983
TL;DR: In this article, the authors described a mechanism for the separation and elimination of unimportant reactions with the aid of the present kinetic data for the elementary reactions involved, which explains, without fitting, the currently available experimental results for laminar premixed flames of alkanes, alkenes and acetylene.
Abstract: The detailed knowledge of combustion mechanisms is important, for example for the control of (kinetically determined) pollutant formation (e.g. NO, hydrocarbons, soot), for ignition problems, or for the extrapolation to technologically important but experimentally inaccessible condition. – In this review it is described how by suitable separation and elimination of unimportant reactions a mechanism is developed with the aid of the present kinetic data for the elementary reactions involved. This mechanism explains, without fitting, the currently available experimental results for laminar premixed flames of alkanes, alkenes and acetylene (flame velocity and structure of free flames, concentration and temperature profiles in burner-stabilized flames). These experimental results are simulated by the solution of the corresponding conservation equations with suitable models describing diffusion and heat conduction in the multicomponent mixture considered. – In lean and moderately rich flames the hydrocarbon is attacked by O, H, and OH in the first step. These radicals are produced by the chain-branching steps of the oxyhydrogen reaction. The alkyl radicals formed in this way always decompose to smaller alkyl radicals by fast thermal elimination of alkenes. Only the relatively slow thermal decomposition of the smallest alkyl radicals (CH3 and C2H5) competes with recombination and with oxidation reactions by O atoms and O2. This part of the mechanism is rate-controlling in the combustion of alkanes and alkenes, and is therefore the reason for the similarity of all alkane and alkene flames. – In rich flames of aliphatic fuels, acetylene becomes a very important intermediate leading to soot precursors and to Non-Zeldovich-NO. Details of the reaction mechanisms are not yet known.
105 citations
TL;DR: In this article, it was shown that the observed preexponential factors for such reactions are generally one-to-three orders of magnitude lower than those for the desorption of the same molecules, which is explained within transition state theory as being due to the conversion of highly excited low energy motions in the adsorbed molecule to unexcited vibrational modes in the transition state.
104 citations
TL;DR: An existing, validated elementary reaction model for hydrogen oxidation in supercritical water, with theoretically consistent modifications for high pressure, was expanded to allow modeling of carbon monoxide oxidation as discussed by the authors.
Abstract: An existing, validated elementary reaction model for hydrogen oxidation in supercritical water, with theoretically consistent modifications for high pressure, was expanded to allow modeling of carbon monoxide oxidation The carbon monoxide model was less successful, exhibiting a higher overall activation energy than the data and lacking an oxygen dependence Data for fuel-rich CO oxidation, including hydrogen formation, were well predicted, but results for fuel-lean conditions were not correctly predicted Both models, when extended to subcritical conditions, successfully reproduced the majority of the experimentally observed pressure (water-density) dependence
104 citations
TL;DR: In this article, the authors present a density-functional-theory study of formaldehyde and methanol synthesis from CO and H2 on a Ni catalyst and calculate the reaction enthalpy and energy barrier for each elementary reaction.
Abstract: We present a density-functional-theory study of formaldehyde and methanol synthesis from CO and H2 on a Ni catalyst We investigate the intermediate products of the reaction and calculate the reaction enthalpy and energy barrier for each elementary reaction, taking into account several different adsorption geometries and the presence of isomers of the intermediate products Hydrogenation of CO is favored over desorption or dissociation of CO on flat Ni(111), to form the formyl radical (HCO) or its isomer, COH Subsequent hydrogenation leads to formaldehyde (CH2O), methoxy (CH3O), and, finally, methanol (CH3OH) The overall reaction barrier for formaldehyde and methanol formation is 20 eV
103 citations