Kinetics of Methane Oxidation

Skinner, Geoff; Lifshitz, Assa; Scheller, Karl; Burcat, Alexander

doi:10.1063/1.1677790

Cited by 94 publications

(24 citation statements)

References 10 publications

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“…CH2 is mainly produced via ethyne. This route has been shown to be minor in the combustion of methane (Walrnatz, 1983), and CO formation via these radicals is difficult (Skinner et al, 1972).…”

Section: Network Construction and Parameter Estimationmentioning

confidence: 99%

Kinetics of the oxidative coupling of methane at atmospheric pressure in the absence of catalyst

Chen

Hoebink

Marin

1991

Ind. Eng. Chem. Res.

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Continuous flow experiments for the oxidative coupling of methane in the absence of catalyst and at low methane conversion were carried out in empty tubular quartz reactors at atmospheric pressure, temperatures from 873 to 1123 K, and inlet molar ratios of CH,/O2 from 4 to 10 and of He/CH4 from 0 to 1.25. The methane conversion varied from 2 to 15% and the oxygen conversion from 10 to 100%. A reaction network was constructed on the basis of elementary free-radical reactions. Arrhenius parameters were estimated for the most important reactions by regression of experimental data. The effects of the process conditions on the conversions of methane and oxygen as well as on the selectivities toward products were simulated adequateliy by considering 33 elementary reactions.Ethane is mainly formed from the recombination of methyl radicals arising from degenerate branched chains involving OH and H 0 2 as main chain carriers. Etlhene originates from ethane mainly via a pyrolytic chain, while the oxidative dehydrogenation contributes to a much lower extent. Carbon monoxide originates from the oxidation of methyl radicals, whereas the contribution of the consecutive oxidation is not significant a t the conversion levels investigated. IntroductionThe oxidative coupling of methane aimed at the production of higher hydrocarbons has attracted much attention during the past years. This reaction is usually carried out in the presence of catalysts and requires temperatures up to 1150 K. At these temperatures, noncatalytic reactions in the gas phase, however, play an essential role in the formation of higher hydrocarbons. It is generally accepted that the most widely studied alkali metal/&aline earth metal oxide and the rare earth metal oxide catalysts act as a methane activator and in particular as a producer of methyl radicals, with the subsequent reactions taking place in the gas phase (Ito et al., 1985). Whether or not the reducible multivalent metal oxides catalyze the reactions in the same way is still in debate.The importance of the gas-phase reactions has been well recognized and is reflected in several recent papers on the oxidative coupling of methane in the absence of catalyst (Labinger and Ott, 1987;Lane and Wolf, 1988;Geerts et al., 1990;Zanthoff and Baerns, 1990). Furthermore, in a recent review, Lunsford (1990) has pointed out the importance of branched-chain reactions in the gas phase with respect to the generation of methyl radicals. Consequently, Lunsford proposed that catalysts might be an important initiator of the chain reaction, but not a major source of methyl radicals. Kinetic models based on the free-radical mechanism have been set up in order to understand the role played by the gas-phase reactions and the interaction between the gas-phase reactions and the reactions on the catalyst surface. The Arrhenius parameters were selected from data bases in the literature that originate mainly from combustion kinetics (Tsang and Hampson, 1986; Warnatz, 1984). While the dependence of the coupling selectivity on co...

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Section: Network Construction and Parameter Estimationmentioning

confidence: 99%

Kinetics of the oxidative coupling of methane at atmospheric pressure in the absence of catalyst

Chen

Hoebink

Marin

1991

Ind. Eng. Chem. Res.

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“…It attains a steady-state concentration, and its slow reactions lead to a buildup of a radical pool, namely, H, 0, HOz, and OH, which accelerates methane consumption during the chain-branching phase. In a numerical model for the initiation of methane combustion, Westbrook [5] utilized the thermal decomposition of CH4 for the formation of methyl radicals, (6) CH4 + M -CH3 + H + M Other authors [6,7] have contended that below 1700 K the reaction between 0 2 and CH4 is more important, namely,…”

Section: (4)mentioning

confidence: 99%

“…This observation was especially interesting in view of the controversy which has existed recently concerning the reaction of methyl radicals with molecular oxygen. A number of investigators, such as Skinner et al [6] and Bowman [El, have included the formation of H2CO and its subsequent decomposition to account for their kinetic data and for the early appearance of CO in methane flames. Peeters and Mahnen [ 161 sampled and analyzed by mass spectrometry a methane flame to demonstrate the transitory existence of CHzO with a maximum concentration at about 1200 K. Although the reaction between methyl and 0 2 has frequently been considered to be (9) CH3 + 0 2 -+ CH2O + OH the role of this process has been questioned.…”

Section: Reaction Between Ch4 and 12mentioning

confidence: 99%

Kinetics of the reaction between methane and iodine from 830 to 1150 K in the presence and absence of oxygen

Pardini

Martin

1983

Int J of Chemical Kinetics

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The formation of methyl iodide was determined by radiochemical methods and by massspectroscopic analyses in mixtures of Ar-CH4-12 and Ar-CH4-12-02, heated by a reflected shock wave to temperatures of 830-1150 K. The rate of formation of CH3I was consistent with the chain mechanism I + CH4-CH3 + HI CH3 + 12 CH31 + I where the indicated rate constant for reaction between I and CH4 is given by k2(cm3/mol s) = 1014.17 exp(-32.9 f 0.8 kcal/mol/RT). No effect on the reaction rate by the presence of 0 2 was detected. However, in one experiment at 1097 K with 3.86 mol ' % 0 2 the formation of CHzO was indicated by the mass-spectroscopic analysis, presumably from the reaction of 0 2 with CH3.

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“…In particular, the ignition delay of methane-oxygen-argon mixtures has been extensively investigated experimentally (Lifshitz et al, 1971), and supported by numerical computer modeling using suitable detailed chemical kinetics (Skinner et al, 1972). Experiments and chemical kinetic modelling of the oxidation of various blends of methane and propane were also performed (Peterson et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Constant Volume Autoignition of Premixed Methane-Carbon Dioxide Mixtures

Thiessen

Karim

Seyedeyn-Azad

2007

International Journal of Green Energy

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Mounting concerns about green house gas emissions as well as increasing demands for energy have been encouraging the use of alternative fuels such as those gases derived from biomasses, which are made up primarily of methane and carbon dioxide. Safety and potential hazard considerations associated with such usage require additional information about the autoignition behaviour of such fuel-air systems when heated. Accordingly, their behaviour was analytically investigated for a homogeneous CH 4 -O 2 -CO 2 system under constant volume conditions where the dependence of pre-ignition reaction activity and the associated ignition delay were investigated over a wide range of initial key operating parameters, including initial temperature, pressure and mixture composition. These results were compared with the corresponding behaviour of CH 4 -O 2 -N 2 . The role of speeding the reaction rates of such mixtures through the addition of hydrogen was also investigated.

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Kinetics of Methane Oxidation

Cited by 94 publications

References 10 publications

Kinetics of the oxidative coupling of methane at atmospheric pressure in the absence of catalyst

Kinetics of the oxidative coupling of methane at atmospheric pressure in the absence of catalyst

Kinetics of the reaction between methane and iodine from 830 to 1150 K in the presence and absence of oxygen

Constant Volume Autoignition of Premixed Methane-Carbon Dioxide Mixtures

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