A general mechanism for the high-temperature pyrolysis of alkanes. The pyrolysis of isobutane

1974 ◽  
Vol 337 (1609) ◽  
pp. 199-216 ◽  
Keyword(s):  
Experimental Data ◽  
Computer Modelling ◽  
Single Pulse ◽  
General Mechanism ◽  
Methyl Radical ◽  
Hydrogen Atoms ◽  
Wide Range ◽  
Independent Experimental Data ◽  
Theoretical Considerations ◽  
Kinetics Of

A general mechanism is proposed to predict the kinetics of pyrolysis of alkanes at high temperatures (> 1000 K), based on theoretical considerations and on existing literature data. An experimental investigation of the pyrolysis of isobutane in a single-pulse shock tube over the temperature range 1200–1500 K is reported and the results are used to test the proposed mechanism. Computer modelling demonstrates that the mechanism is adequate to explain the experimental data provided that the following are included: ‘forbidden' isomerization reactions, non-Arrhenius rate constants for the methyl radical abstraction reactions, and the addition of hydrogen atoms to olefins. Although further refinement of the mechanism is to be expected as more data becomes available, it already enables pyrolytic behaviour to be predicted for a wide range of alkanes. The investigation also demonstrates how computer modelling can provide insight into a reaction mechanism even when the number of unknowns exceeds the independent experimental data available.

Reactions of free radicals with aromatic compounds in the gaseous phase. I. Kinetics of the reaction of methyl radicals with toluene

1964 ◽  
Vol 17 (12) ◽  
pp. 1329 ◽  
Author(s):  
MFR Mulcahy ◽  
DJ Williams ◽  
JR Wilmshurst
Keyword(s):  
Flow System ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Hydrogen Atoms ◽  
Methyl Group ◽  
Benzyl Radical ◽  
Toluene Molecule ◽  
Benzyl Radicals ◽  
Butyl Peroxide ◽  
Kinetics Of

The kinetics of abstraction of hydrogen atoms from the methyl group of the toluene molecule by methyl radicals at 430-540�K have been determined. The methyl radicals were produced by pyrolysis of di-t-butyl peroxide in a stirred-flow system. The kinetics ,agree substantially with those obtained by previous authors using photolytic methods for generating the methyl radicals. At toluene and methyl-radical concentrations of about 5 x 10-7 and 10-11 mole cm-3 respectively the benzyl radicals resulting from the abstraction disappear almost entirely by combination with methyl radicals at the methylenic position. In this respect the benzyl radical behaves differently from the iso-electronic phenoxy radical, which previous work has shown to combine with a methyl radical mainly at ring positions. The investigation illustrates the application of stirred-flow technique to the study of the kinetics of free-radical reactions.

scholarly journals Comparison of discontinuous damage models of Mullins-type

2021 ◽  
Vol 91 (10) ◽  
pp. 4097-4119
Author(s):  
Alexander Ricker ◽  
Nils Hendrik Kröger ◽  
Peter Wriggers
Keyword(s):  
Experimental Data ◽  
Characteristic Property ◽  
Pure Shear ◽  
Constitutive Models ◽  
Mullins Effect ◽  
Damage Models ◽  
Filled Rubber ◽  
Wide Range ◽  
Theoretical Considerations

AbstractThe Mullins effect is a characteristic property of filled rubber materials whose accurate and efficient modelling is still a challenging task. Innumerable constitutive models for elastomers are described in the literature. Therefore, this contribution gives a review on some widely used approaches, presents a classification, proves their thermodynamic consistency, and discusses reasonable modifications. To reduce the wide range of models, the choice is restricted to those which reproduce the idealised, discontinuous Mullins effect. Apart from the theoretical considerations, two compounds were produced and tested under cyclic uniaxial and equibiaxial tension as well as pure shear. Based on this experimental data, a benchmark that compares the fitting quality of the discussed models is compiled and favourable approaches are identified. The results are a sound basis for establishing novel or improving existing rubber models.

Improved Measurement of the Kinetics of Crystallization in a Batch Experiment

1993 ◽  
Vol 58 (8) ◽  
pp. 1839-1847 ◽  
Author(s):  
Jaroslav Nývlt ◽  
Miloslav Karel
Keyword(s):  
Experimental Data ◽  
Crystal Size ◽  
Evaluation Method ◽  
Potassium Sulfate ◽  
Batch Experiment ◽  
Improved Method ◽  
Short Intervals ◽  
Wide Range ◽  
Kinetics Of ◽  
Single Batch

An improved method is described whereby knowledge of the supersaturation course during a run and measurement of the final product crystal size distribution yield the growth rate of crystals and the nucleation rate in a wide range of supersaturations from only a single batch experiment. The evaluation method is refined by the interpolation of experimental data for short intervals of time. The method is illustrated using potassium sulfate crystallization as an example.

An expression for droplet evaporation incorporating thermal effects

2011 ◽  
Vol 667 ◽  
pp. 260-271 ◽  
Author(s):  
K. SEFIANE ◽  
R. BENNACER
Keyword(s):  
Experimental Data ◽  
Thermal Effects ◽  
Droplet Evaporation ◽  
Theoretical Expression ◽  
Dimensionless Number ◽  
Wide Range ◽  
Isothermal Diffusion ◽  
Rate Of Evaporation ◽  
First Time ◽  
Kinetics Of

We propose a general theoretical expression for sessile droplets' evaporation, incorporating thermal effects related to the thermal resistance of the substrate and liquid properties. We develop an expression which accounts for thermal effects associated with evaporative cooling; the latter leads to a reduction in the rate of evaporation, which is not accounted for in the current theories, i.e. ‘isothermal diffusion theories’. The threshold for transition to a regime in which thermal effects start to be significant is identified through a dimensionless number which includes substrate and liquid properties as well as the kinetics of evaporation. The proposed theory is validated against experimental data in a very wide range of conditions and for a variety of systems. The developed expression extends the domain of use of diffusion-based models for droplet evaporation and accurately describes some aspects of the phenomenon which, to the best of our knowledge, are highlighted for the first time.

Kinetics of the Luminescence of Isoelectronic Rare-Earth Ions In III-V Semiconductors

1993 ◽  
Vol 301 ◽  
Author(s):  
H.J. Lozykowski
Keyword(s):  
Experimental Data ◽  
Energy Transfer ◽  
Rare Earth ◽  
Excited States ◽  
Quantitative Agreement ◽  
Host Lattice ◽  
Rare Earth Ions ◽  
Wide Range ◽  
Decay Times ◽  
Kinetics Of

ABSTRACTIn this work we have developed a model for the kinetics of the energy transfer from the host lattice to the localized core excited states of rare earth isoelectronic structured traps (REI-trap). We have derive a set of differential equations for semi-insulating semiconductor governing the kinetics of rare earth luminescence. The numerically simulated rise and decay times of luminescence show a good quantitative agreement with the experimental data obtained for InP:Yb, over a wide range of generation rates.

Chemisorption of hydrogen on nickel–magnesia catalysts. Part I. General kinetic characteristics

1969 ◽  
Vol 47 (16) ◽  
pp. 2933-2941 ◽  
Author(s):  
N. S. Viswanathan ◽  
L. M. Yeddanapalli
Keyword(s):  
Experimental Data ◽  
Nickel Catalysts ◽  
Activation Energies ◽  
Effect Of Temperature ◽  
Hydrogen Chemisorption ◽  
Kinetic Characteristics ◽  
Wide Range ◽  
Elovich Equation ◽  
Kinetics Of

A detailed study of the kinetics of hydrogen chemisorption on 3 different nickel catalysts, supported on magnesia and prepared by coprecipitation, has been made over a wide range of pressures and temperatures. The results have been analyzed in the light of the Elovich equation. Experimental data obtained by variations of pressure and temperature indicate the existence of a number of stages in the chemisorption process and support the multiple kinetic stage hypothesis suggested by Low. The effect of temperature on the parameters has been studied, and relations obtained which have been used to calculate activation energies for each of the stages.

Isothermal Dehydriding Kinetics of Mg2NiH4 Prepared under an External Magnetic Field

2013 ◽  
Vol 785-786 ◽  
pp. 638-641
Author(s):  
Jing Liu
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Solid Solution ◽  
External Magnetic Field ◽  
Magnetic Intensity ◽  
Hydrogen Atoms ◽  
Kinetics Of ◽  
Rate Controlling Step ◽  
Diffusion Of Hydrogen ◽  
Good Agreement

The Mg2NiH4hydrogen storage metal hydride was prepared by hydriding combustion synthesis under an external magnetic field. The dehydriding kinetics of the hydrides was measured under isotherm condition. The kinetics mechanism of Mg2NiH4materials was analyzed by model. The calculated results show that the theoretical calculation and the experimental data can reach a good agreement. The rate-controlling step is the diffusion of hydrogen atoms in the solid solution. The dehydriding activation energies of the sample synthesized under the optimized magnetic intensity of 6 T is 104 kJ/mol H2.

Autowave Features of Plastic Deformation by Ductile Fracture

2013 ◽  
Vol 592-593 ◽  
pp. 664-667
Author(s):  
Dina Orlova ◽  
Vladimir Danilov ◽  
Lev B. Zuev
Keyword(s):  
Experimental Data ◽  
Plastic Deformation ◽  
Dissipative Structure ◽  
Vector Fields ◽  
Displacement Vector ◽  
Speckle Photography ◽  
Metallic Materials ◽  
Deformation Localization ◽  
Wide Range ◽  
Kinetics Of

The kinetics of fracture was examined for a wide range of metallic materials. Using speckle photography technique, displacement vector fields were recorded for the deforming sample. The deformation localization is an autowave process, which manifests macroscopic inhomogeneities from yield point to necking. This involves a changeover in the autowave types: phase autowave stationary dissipative structure propagating autowave collapse of autowave. The loading curves obtained for all studied materials have a similar autowave pattern emerging at the pre-fracture stage, no matter what is crystalline or microstructural state of material. Using experimental data on the kinetics of autowave collapse, the space-time coordinates of failure can be predicted for the object under load long before symptoms of fracture are detected visually.

scholarly journals The kinetics of the interaction of atomic hydrogen with olefines I. Apparatus and use of para-hydrogen techniques

1949 ◽  
Vol 196 (1047) ◽  
pp. 445-465 ◽  
Keyword(s):  
Hydrogen Atom ◽  
Saturated Hydrocarbon ◽  
Oxide Surface ◽  
Para Hydrogen ◽  
Hydrocarbon Molecule ◽  
Hydrogen Atoms ◽  
Collision Efficiency ◽  
Wide Range ◽  
New Type ◽  
Kinetics Of

It is shown in this paper that the normal techniques and methods of approach to an investigation of radical reactions are not applicable in dealing with reactions involving the addition of a hydrogen atom to an olefine, since this type of reaction is so fast that even the exchange conversion of para-hydrogen by hydrogen atoms is inhibited by very small amounts of olefines. A new type of reaction has been utilized to provide a means of competing with the olefine for a hydrogen atom, namely, the removal of a hydrogen atom on a layer of molybdenum oxide or tungsten oxide. In order to adapt the system to the measurement of reactions over a wide range of collision efficiency, a special reaction vessel is described in which the path length offered to a hydrogen atom before removal on the oxide layer can be varied. A colorimetric technique has been devised for measuring the rate of addition of hydrogen atoms to the oxide surface. This technique is shown to be very sensitive, and the addition of a very small amount of hydrogen atoms can be detected. The para-hydrogen conversion technique has been applied to illustrate how the collision efficiency of a hydrogen atom with a saturated hydrocarbon molecule can be obtained. The reaction H + R H = H 2 + R has approximately the same collision efficiency as the reaction H + p -H 2 = n -H 2 + H, and hence in the presence of a saturated hydrocarbon there is no inhibition of the para-conversion, only retardation. A further application of the para-conversion has been to demonstrate the efficiency of the removal of a hydrogen atom on the oxides of molybdenum and tungsten.

A fuzzy neural network approach for modeling the growth kinetics of FeB and Fe2B layers during the boronizing process

2018 ◽  
Vol 106 (6) ◽  
pp. 603 ◽  
Author(s):  
Bendaoud Mebarek ◽  
Mourad Keddam
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Fuzzy Neural Network ◽  
Treatment Time ◽  
Calculation Model ◽  
Average Error ◽  
Network Approach ◽  
Neural Network Approach ◽  
Fuzzy Neural ◽  
Kinetics Of

In this paper, we develop a boronizing process simulation model based on fuzzy neural network (FNN) approach for estimating the thickness of the FeB and Fe2B layers. The model represents a synthesis of two artificial intelligence techniques; the fuzzy logic and the neural network. Characteristics of the fuzzy neural network approach for the modelling of boronizing process are presented in this study. In order to validate the results of our calculation model, we have used the learning base of experimental data of the powder-pack boronizing of Fe-15Cr alloy in the temperature range from 800 to 1050 °C and for a treatment time ranging from 0.5 to 12 h. The obtained results show that it is possible to estimate the influence of different process parameters. Comparing the results obtained by the artificial neural network to experimental data, the average error generated from the fuzzy neural network was 3% for the FeB layer and 3.5% for the Fe2B layer. The results obtained from the fuzzy neural network approach are in agreement with the experimental data. Finally, the utilization of fuzzy neural network approach is well adapted for the boronizing kinetics of Fe-15Cr alloy.

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