Kinetics and mechanism of the thermal decomposition of methane in a flow system

Palmer, Howard B.; Lahaye, J.; Hou, K. C.

doi:10.1021/j100847a068

Cited by 73 publications

(36 citation statements)

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“…Autocatalysis is most evident in the yield of ethane, but affects the other products as well, although it is less obvious because their yields are already rising sharply. Autocatalysis has frequently been reported in the decomposition of methane, and under various conditions of pressure, temperature, conversion or surface, may have a variety of causes (10)(11)(12)(13). It has been attributed to reactions occurring on the surface of the vessel, possibly catalysed by a carbon film (14,15).…”

Section: Autocataljsis Carbon Forrimtion and Surfacementioning

confidence: 99%

The thermal decomposition of methane. II. Secondary reactions, autocatalysis and carbon formation; non-Arrhenius behaviour in the reaction of CH₃ with ethane

Chen¹,

Back²,

Back³

1976

Can. J. Chem.

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In the thermal decomposition of methane at temperatures from 880 to 1103 K, hydrogen and ethane are the only primary products. The rate of formation of ethane falls rapidly towards zero as the reaction progresses until ethane reaches a steady-state concentration. This behaviour is interpreted in terms of a radical chain mechanism,[Formula: see text]Values of k4 were obtained which confirm the non-Arrhenius behaviour of this reaction at these temperatures. Similar chain sequences propagated by addition or abstraction reactions of methyl radicals with ethylene, propylene, and acetylene can account for the formation and disappearance of these secondary products.At a later stage in the pyrolysis a marked autocatalysis is observed and the yield of ethane increases sharply above its steady-state value. It is concluded that this autocatalysis is largely a homogeneous process and is not caused by or associated with carbon formation. Deposition of carbon on the surface was observed at a still later stage of the decomposition, and was quantitatively estimated by light absorption measurements. Possible mechanisms for the auto catalysis are discussed.

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Section: Autocataljsis Carbon Forrimtion and Surfacementioning

confidence: 99%

The thermal decomposition of methane. II. Secondary reactions, autocatalysis and carbon formation; non-Arrhenius behaviour in the reaction of CH₃ with ethane

Chen¹,

Back²,

Back³

1976

Can. J. Chem.

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“…As [4] and [5] [4] and [5].3 These and other subsequent secondary reactions will not be discussed further in the present paper which is concerned chiefly with the rate of [I].…”

Section: Secondary Reactionsmentioning

confidence: 99%

“…Values of R0 for ethane and hydrogen can be obtained directly from yield-time plots, but because [.4] and [5] set in at very low conversion, accurate initial rates could not always be measured. Roc,,, may also be equated to R(c2H6+c2H,, or to +R(H2+c2H6,, which corrects for loss of ethane in [4] the best fit, and this was the method finally employed. Values of the rate constant, k,, obtained in this way over a range of temperature and pressure are given in Table 3.…”

Section: Measurement Of Kmentioning

confidence: 99%

“…[Traduit par le journal] Introduction Although the pyrolysis of methane has been studied many times before, important details of the reaction mechanism have remained obscure (1)(2)(3)(4)(5). It is well established that the initial products are C2H6 and Hz, and in some shock-tube experiments the pyrolysis has been effectively limited to this ftage and initial rates measured.…”

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confidence: 99%

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The Thermal Decomposition of Methane. I. Kinetics of the Primary Decompositionto C₂H6 + H₂; Rate Constant for the Homogeneous Unimolecular Dissociation of Methane and its Pressure Dependence

Chen¹,

Back²,

Back³

1975

Can. J. Chem.

137

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The pyrolysis of methane has been studied in a static system at temperatures of 995, 1038, 1068, and 1103 K and pressures from 25 to 700 Torr. It was concluded that the initial stages of the reaction can be described by a simple homogeneous, nonchain radical mechanism:[Formula: see text]Initial rates of reaction were measured, based on analysis of hydrogen, ethane, and ethylene, and k1 was found to be pressure dependent and homogeneous. Quantitative agreement was obtained with values of k1 calculated by R.R.K.M. theory. Values of A∞ = 2.8 × 1016 s−1 and E∞ = 107.6 kcal/mol were obtained, the latter appreciably greater than the value of E0 = 103 kcal/mol used in the calculations. Comparison of previous shock-tube and flow-system data at temperatures up to 2200 K showed good agreement with values of k1 obtained by extrapolation of the present R.R.K.M. calculations. It was concluded that in all previous studies, the initial dissociation was in its pressure-dependent region. Estimates were also made of the rate constant for the reverse of [1] and showed fair agreement with recent experimental measurements.

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“…Dissociation of methane is an example of an initiation reaction with a high activation energy. As shown by Palmer et al, [6] it may vary from about 350 kJ mol ±1 to about 432 kJ mol…”

Section: Introductionmentioning

confidence: 81%

Determination of the Kinetics of CVD in Hot Wall Reactors

Hüttinger

2000

Chem. Vap. Deposition

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CVD of pyrolytic carbon from methane was studied as a model reaction to demonstrate the influence on deposition kinetics of the variation of i) the volume flow rate (leading to different initial conditions) and ii) the substrate surface area, or substrate surface area/reactor volume ratio (third parameter of CVD). The experiments were performed at an ambient pressure of about 100 kPa, a methane partial pressure of 10 kPa, and a temperature of 1100 C. Carbon deposition rates as a function of reactor/substrate length were studied at three different volume flows, or total residence times, using three substrates with different surface area/reactor volume ratios, (A S /V R ). Additionally, compositions of the gas phase were determined. Changing the volume flow leads not only to different initial conditions but also to different deposition rates as a function of residence time, in contrast to a homogeneous reaction. Experiments with substrates exhibiting different A S /V R ratios confirm earlier results that a broad variety of deposition kinetics can be obtained by changing this ratio.

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Kinetics and mechanism of the thermal decomposition of methane in a flow system

Abstract: If Lo and Vo are constant, the value of C appearing in eq 2 and 3 is a constant. Slight variations in Lo and Vo affect C as shown in eq A2. This variation of C can be accounted for in eq 2 and 3.On the Kinetics and Mechanism of the Thermal Decomposition of Methane in a Flow System1 by .

Cited by 73 publications

References 1 publication

The thermal decomposition of methane. II. Secondary reactions, autocatalysis and carbon formation; non-Arrhenius behaviour in the reaction of CH₃ with ethane

The thermal decomposition of methane. II. Secondary reactions, autocatalysis and carbon formation; non-Arrhenius behaviour in the reaction of CH₃ with ethane

The Thermal Decomposition of Methane. I. Kinetics of the Primary Decompositionto C₂H6 + H₂; Rate Constant for the Homogeneous Unimolecular Dissociation of Methane and its Pressure Dependence

Determination of the Kinetics of CVD in Hot Wall Reactors

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Kinetics and mechanism of the thermal decomposition of methane in a flow system

Abstract: If Lo and Vo are constant, the value of C appearing in eq 2 and 3 is a constant. Slight variations in Lo and Vo affect C as shown in eq A2. This variation of C can be accounted for in eq 2 and 3.On the Kinetics and Mechanism of the Thermal Decomposition of Methane in a Flow System1 by .

Cited by 73 publications

References 1 publication

The thermal decomposition of methane. II. Secondary reactions, autocatalysis and carbon formation; non-Arrhenius behaviour in the reaction of CH3 with ethane

The thermal decomposition of methane. II. Secondary reactions, autocatalysis and carbon formation; non-Arrhenius behaviour in the reaction of CH3 with ethane

The Thermal Decomposition of Methane. I. Kinetics of the Primary Decompositionto C2H6 + H2; Rate Constant for the Homogeneous Unimolecular Dissociation of Methane and its Pressure Dependence

Determination of the Kinetics of CVD in Hot Wall Reactors

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The thermal decomposition of methane. II. Secondary reactions, autocatalysis and carbon formation; non-Arrhenius behaviour in the reaction of CH₃ with ethane

The thermal decomposition of methane. II. Secondary reactions, autocatalysis and carbon formation; non-Arrhenius behaviour in the reaction of CH₃ with ethane

The Thermal Decomposition of Methane. I. Kinetics of the Primary Decompositionto C₂H6 + H₂; Rate Constant for the Homogeneous Unimolecular Dissociation of Methane and its Pressure Dependence