Showing papers on "Elementary reaction published in 1976"
TL;DR: In this article, the authors showed that fuel-nitrogen fed as ammonia or as pyridine to rich flames is mainly present in the burnt gas in the forms HCN, NH3, NO and N2.
151 citations
TL;DR: In this article, the authors consider the local rate of reaction in a fluid phase as a function of state variables, r(C, p, T), and describe the rate in terms of a sequence of elementary steps, providing all the active intermediates are known.
Abstract: It is possible to consider the local rate of reaction in a fluid phase as a function of state variables, r(C, p, T). We assume that the concentrations of all the components C, which may, for example, be important in initiation and termination are included in the description. The rate must also be slow compared to other phenomena which might create a nonuniform mixture on the scale in which we are interested. If these restrictions are respected, we then can describe the rate in terms of a sequence of elementary steps, providing all the active intermediates are known. For gases the rate parameters (frequency factors, activation energy) for many elementary reactions have been measured; these matters are discussed, for example, in the book by Johnston [l]. The rate r (g-mole/cm3-sec) is in a certain sense a state function; it becomes related to a derivative or other quantities only as it appears in the conservation equations.
139 citations
132 citations
TL;DR: In this article, the effects of strain rate, applied potential, pH, temperature, and hydrogen sulfide concentration on sulfide cracking of mild steel were examined at constant strain rates by means of an Instron-type machine.
Abstract: Effects of strain rate, applied potential, pH, temperature, and hydrogen sulfide concentration on sulfide cracking of mild steel were examined at constant strain rates by means of an Instron-type machine. Fractographic observations were also carried out on a scanning electron microscope. Kinetic studies were also made to elucidate the hydrogen electrode reaction mechanism for mild steel and the effect of hydrogen sulfide on the reaction. Amount of hydrogen absorbed in mild steels stressed at a constant strain rate was measured and relationship of hydrogen embrittlement of mild steel with hydrogen electrode reaction and hydrogen absorption in hydrogen sulfide solutions was investigated. Fracture surfaces were transgranular quasi-cleavage and nucleation sites of cracks appeared to be carbides in the pearlite, inclusions and/or grain boundaries. The elementary reactions of hydrogen electrode reaction in acidic solutions are proton discharge and recombination of adsorbed hydrogen atoms and the rate d...
90 citations
TL;DR: In this article, the rate constants (cm3/molec · sec) k1, k2, and k3 were determined using atomic resonance fluorescence in discharge flow systems.
Abstract: Direct determinations of the rate constants (cm3/molec · sec) k1, k2, and k3 from 298 to 299°K are reported, using atomic resonance fluorescence in discharge flow systems:
1
The rate constant k1, which has not been determined previously, was found to possess an insignificant temperature coefficient (EA = (0 ± 700) J/mole) in the range of 299 to 619°K.
The present result for k2 agrees well with reinterpreted values from the one previous determination. Measurements of O atom consumption rates and Br atom production rates in the O + Br2 reaction are interpreted to give an estimate of the rate constant k4, which has not been reported previously, at 298°K:
k3 has been measured at three temperatures between 299 and 602°K. The present and previous results for k3 were combined to give the following rate expression:
54 citations
TL;DR: The rate of chemical-initiated bulk polymerization is studied theoretically and experimentally over the complete course of reaction taking into consideration the effects of the decrease of jump frequency of a polymer segment during polymerization on the rate of each elementary reaction.
Abstract: The rate of chemical-initiated bulk polymerization is studied theoretically and experimentally over the complete course of reaction Taking into consideration the effects of the decrease of jump frequency of a polymer segment during polymerization on the rate of each elementary reaction, a new kinetic model is proposed This model is applied to the bulk polymerization of methyl methacrylate and styrene for several initiator concentrations and temperatures Though the polymerization of these monomers shows very different auto-acceleration effects, experimental data of conversion and number-average and weight-average chain length can be successfully correlated to limiting conversion by this model
50 citations
TL;DR: In this paper, the microstructure of low-pressure methane-oxygen-argon flames was investigated using modulated molecular beam-mass spectrometry (MBS) using profiles of radical and stable species concentration, temperature, and area expansion ratio.
36 citations
TL;DR: In this paper, the rate of reaction of muonium atoms with bromine molecules in an argon moderator gas at a atm and 23°C was measured and the bimolecular rate constant was k = (2.4±0.3) ×1011 l/mole−sec, ten times higher than that for the analogous reaction of hydrogen atoms.
Abstract: We report a precise measurement of the rate of reaction of muonium atoms with bromine molecules in an argon moderator gas at a atm and 23 °C. The bimolecular rate constant is k= (2.4±0.3) ×1011 l/mole‐sec, ten times higher than that for the analogous reaction of hydrogen atoms. Since muonium can properly be treated as a light isotope of hydrogen, this comparison has potential significance for the theory of reaction rates. The technique is described and the results discussed.
33 citations
TL;DR: The rate constant k1 for the reaction Cl 2P+O3→ ClO + O2(1) has been measured over the temperature range 221 −629 K as discussed by the authors.
Abstract: The rate constant k1 for the reaction Cl 2P+ O3→ ClO + O2(1) has been measured over the temperature range 221–629 K. Atomic resonance absorption with a metastable Ar lamp, which emits non-reversed thermal Cl atom lines, was used to follow the pseudo first order decay of [Cl] in excess of O3. The Arrhenius expression is given as log10(k1/cm3 molecule–1 s–1)=–(10.286 ± 0.039)–[(181 ± 12)/T]. Comparisons with other recent measurements are made.
28 citations
TL;DR: In this article, the authors derived approximate analytical solutions for the reaction factor based on the film and penetration theories for the case where the first reaction step is an irreversible second order reaction with a finite reaction rate and the second step is a instantaneous reversible reaction.
20 citations
TL;DR: In this paper, the distribution of the kinetic energy release for reactions of metastable ions leading to the formation of the benzoyl cation was determined for simple bond cleavages, and the shapes of these distributions varied widely, as did the magnitude of the most probable energy release.
Abstract: Distributions of the kinetic energy release have been determined for reactions of metastable ions leading to formation of the benzoyl cation. Although the reactions studied were all apparent simple bond cleavages, the shapes of these distributions varied widely, as did the magnitude of the most probable energy release. There is evidence that the shape of the distribution function is related to the mechanism of the reaction. In one case the distribution shows structure not seen in the metastable peak itself, suggesting that at least two reaction pathways are operative. Thus, the present measurements on energy distributions supplement the information concerning different elementary reactions that can be obtained from the study of metastable peaks.
01 Feb 1976
TL;DR: In this paper, the main peculiarities of free radical reaction kinetics in organic solids are discussed from the point of view of a slightly modified free volume model of molecular mobility, and it is shown that even far separated radical pairs may react in a "static" way via the long range microdilution of the structure.
Abstract: The main peculiarities of free radical reaction kinetics in organic solids are discussed from the point of view of a slightly modified free volume model of molecular mobility. The reaction and diffusion acts are supposed to occur predominantly in “diluted” microzones, the probability of “dilution” depending on the minimal volume needed for reaction or diffusion, and on the energy of a local molecular displacement. It is shown that even far separated radical pairs may react in a “static” way via the long range microdilution of the structure. The model explains the separation-dependent annealing of radical pairs as well as the stepwise annealing of large fractions of quasi-isolated centres and large capture radii for the diffusion limited reaction of the remaining species. Preliminary results concerning the pressure and plastification dependence of the rate constant are also in reasonable agreement with the proposed concept.
TL;DR: In this article, the authors clarified the role of the initiation reaction H2 + NO ⇀ HNO + H (k1) in the system and obtained the rate constants of k1 and k3 as k1 = 1013.5±0.15 exp (−55.2 kcal/RT) (cm3/mole·sec), respectively.
Abstract: The consumption of nitric oxide in the shock-heated nitric oxide, hydrogen, and argon system had been studied and modeled as the chain-branching process containing the reaction H + NO ⇀ N + OH (k3) as a slow-branching step. Through the computer simulation method the authors clarified the role of the initiation reaction H2 + NO ⇀ HNO + H (k1) in the system and obtained the rate constants of k1 and k3 as k1 = 1013.5±0.15 exp (−55.2 kcal/RT) and k3 = 1013.7±0.15 exp (−48.7 kcal/RT) (cm3/mole·sec), respectively. k1 was one order larger than the value obtained in the flame experiment by Halstead and Jenkins.
TL;DR: In this paper, the dependence on the different atomic and molecular elementary reactions of the atomic (molecular) models adopted is demonstrated for some cases such as hydrogen, helium, highly ionized atoms, nitrogen, on the basis of a Maxwellian velocity distribution.
Abstract: The “thermodynamic state“ and the spatial-temporal evolution of the composition of chemically reacting plasmas are generally described by the Boltzmann or Pauli kinetic equations (balance equations for the transfer of particle densities, momentum, and energy for the different chemical species). Due to the numerous difficulties encountered when solving these coupled differential equations, simplifying assumptions are often introduced. The results therefore depend, on the one hand, on the elementary reactions chosen for the model calculations and, on the other hand, on the cross-sections. Vice versa, the interpretation of both the thermodynamic state and the diagnostic measurements is dependent on the kind of elementary reactions introduced in the model. The dependence on the different atomic and molecular elementary reactions of the atomic (molecular) models adopted is demonstrated for some cases such as hydrogen, helium, highly ionized atoms, nitrogen, on the basis of a Maxwellian velocity distribution. As a refined step, deviations from a Maxwellian distribution should be taken into account. Especially treated are: (a) Excited state populations; (b) Calculation of recombination and ionization coefficients; (c) Influence of deviations from a Maxwell distribution of the electrons; (d) Influence of collisions between chemically excited particles. The laser is often used for plasma diagnostic purposes. The influence of the plasma state by a superimposed laser radiation field is briefly treated including photo-ionization and recombination stimulated by one and two laser photons. Omission of these reactions can lead to erroneous interpretation of measurements. Some of the model calculations are compared with experimental results.
TL;DR: In this article, the exchange reaction between deuterium gas and light water was conducted with a nickel electrode under anodic polarization, and the rates of the constituent steps of the hydrogen electrode reaction were determined at various anodic overpotentials through analysis of the isotropic composition of hydrogen gas.
TL;DR: In this article, the non-equilibrium flowfield of a turbulent free jet hydrogen-oxygen diffusion flame is numerically analyzed using an elaborate finite-rate chemistry model and the reaction mechanism adopted for the analysis considers 23 elementary reactions between 9 chemical species (H 2, O 2, H 2 O 2 and O 3 ).
TL;DR: In this paper, the non-equilibrium laminar boundary-layer flow of dissociating air is analyzed using a finite-rate chemistry model with Soret and Dufour effects included in the boundary layer.
26 Jan 1976
TL;DR: In this paper, the rate coefficients of individual elementary reactions as a function of temperature have been used for understanding, prediction and modeling of combustion systems, and a unique experimental method for providing such data has been used over the 300-1700 K range.
Abstract: : Proper understanding, prediction and modeling of combustion systems requires reliable knowledge of the reaction mechanisms and rate coefficients of individual elementary reactions as a function of temperature. This review discusses a unique experimental method for providing such data. This HTFFR method has been used over the 300-1700 K range and is suitable for temperatures up to approx. 2000 K. The reaction Al + CO2 + Al0 + CO is discussed in some detail to illustrate the method, which has thus far been applied to reactions of metal atoms and metal monoxides. A summary of the rate coefficient data obtained in HTFFRs is given and prospects for extensions of the technique to other types of combustion reactions are discussed. (Author)
TL;DR: In this paper, the authors derived quantum mechanical expressions for chemical reaction rate constants in terms of collision rates for a process in which three molecules enter and three emerge, and used them to derive the collision probability of a single molecule entry and an emergence.
Abstract: Quantum mechanical expressions are derived for chemical reaction rate constants in terms of collision rates for a process in which three molecules enter and three emerge.
TL;DR: In this paper, the rate constant of the elementary reaction H + ClH→HCl* + F was found from an analysis of the delay times of the stimulated emission due to the P2(3) and p2(5) transitions in the HF and HCl molecules, respectively, which occurred in a ClF-H2 laser.
Abstract: The rate constant of the elementary reaction H + ClH→HCl* + F was found from an analysis of the delay times of the stimulated emission due to the P2(3) and P2(5) transitions in the HF and HCl molecules, respectively, which occurred in a ClF–H2 laser. This constant was found to be 0.13 ±0.015 μsec–1·Torr–1 = (3.7±0.4)× 10–12 cm3/sec in the temperature range 300–400°K.
TL;DR: In this article, the exchange reaction between deuterium gas and light water was conducted with a nickel electrode under anodic polarization, and the rates of the constituent steps of the hydrogen electrode reaction were determined at various anodic overpotentials through analysis of the isotropic composition of hydrogen gas.
Abstract: The exchange reaction between deuterium gas and light water was conducted with a nickel electrode under anodic polarization. The rates of the constituent steps of the hydrogen electrode reaction were determined at various anodic overpotentials through analysis of the isotropic composition of the hydrogen gas. Reaction route (B H 2 O, or OH − ) was shown to interpret satifactorily the results. The former step is rate-determining under low hydrogen pressures, whereas the latter becomes kinetically important at high hydrogen pressures. Dependence of the individual step rates upon overpotential was discussed.