Catalytic oxidative coupling of methane—reaction engineering aspects and process schemes

Mleczko, Lesław; Baerns, M.

doi:10.1016/0378-3820(94)00121-9

Cited by 123 publications

(78 citation statements)

References 58 publications

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“…[1] Still, some differences are retained in the steady-state reflected in different rates of methane consumption and product formation (Table 4), as well as apparent activation energies that vary from about 100 to 150 kJ·mol -1 (Table 5) The reaction kinetics of the oxidative coupling of methane over alkaline earth oxides, whether pure or doped with alkaline elements, have been studied frequently. [26][27][28][29][30][31][32][33][34][35] Generally, it is proposed that the reaction is initiated heterogeneously on the catalyst surface and continued as homogeneous reaction in the gas phase. [5] The initial step of the selective coupling of two methane molecules is assumed to be the surface-mediated hydrogen atom abstraction from CH 4 according to an Eley-Rideal-type reaction between oxygen adsorbed on the catalyst surface and methane reacting from the gas phase.…”

Section: Discussionmentioning

confidence: 99%

Structure sensitivity of the oxidative activation of methane over MgO model catalysts: I. Kinetic study

Schwach

Hamilton

Thum

et al. 2015

Journal of Catalysis

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The role of surface structure and defects in the oxidative coupling of methane (OCM) was studied over magnesium oxide as a model catalyst. Pure, nano-structured MgO catalysts with varying primary particle size, shape and specific surface area were prepared by sol–gel synthesis, oxidation of metallic magnesium, and hydrothermal post treatments. The initial activity of MgO in the OCM reaction is clearly structure-sensitive. Kinetic studies reveal the occurrence of two parallel reaction mechanisms and a change in the contribution of these pathways to the overall performance of the catalysts with time on stream. The initial performance of freshly calcined MgO is governed by a surface-mediated coupling mechanism involving direct electron transfer between methane and oxygen. The two molecules are weakly adsorbed at structural defects (steps) on the surface of MgO. The proposed mechanism is consistent with high methane conversion, a correlation between methane and oxygen consumption rates, and high C₂H₄ selectivity after short times on stream. The water formed in the OCM reaction causes sintering of the MgO particles and loss of active sites by degradation of structural defects, which is reflected in decreasing activity of MgO with time on stream. At the same time, gas-phase chemistry becomes more important, which includes the formation of ethane by coupling of methyl radicals formed at the surface and the partial oxidation of C₂H₆. The mechanistic concepts proposed in this work (Part I) will be substantiated in Part II by spectroscopic characterization of the catalysts (Schwach et al. [1])

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Section: Discussionmentioning

confidence: 99%

Structure sensitivity of the oxidative activation of methane over MgO model catalysts: I. Kinetic study

Schwach

Hamilton

Thum

et al. 2015

Journal of Catalysis

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“…These include ethylene (by oxidative coupling of methane), [1][2][3] syngas (by partial oxidation with or without simultaneous steam-and/or CO 2 -mediated methane reformation), [4][5][6][7][8] and gasoline/liquid hydrocarbon fuels [9][10][11][12][13][14] that involve either oxidative [1][2][3][4][5][6][7][8][9][10] or nonoxidative [11][12][13][14][15] methane activation. As methane and carbon dioxide are key greenhouse gases responsible for global warming, the current industrial practice of emission and/or flaring of produced methane will be banned in the near future.…”

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confidence: 99%

Simultaneous Conversion of Methane and Methanol into Gasoline over Bifunctional Ga‐, Zn‐, In‐, and/or Mo‐Modified ZSM‐5 Zeolites

2005

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In response to increased energy demands, worldwide efforts have been made over the past 2-3 decades to develop alternative methods for the conversion of methane (a main constituent of natural gas, coal-bed gas, and biogas) into value-added products. These include ethylene (by oxidative coupling of methane), [1][2][3] syngas (by partial oxidation with or without simultaneous steam-and/or CO 2 -mediated methane reformation), [4][5][6][7][8] and gasoline/liquid hydrocarbon fuels [9][10][11][12][13][14] that involve either oxidative [1][2][3][4][5][6][7][8][9][10] or nonoxidative [11][12][13][14][15] methane activation. As methane and carbon dioxide are key greenhouse gases responsible for global warming, the current industrial practice of emission and/or flaring of produced methane will be banned in the near future. The methane produced in remote places must therefore be converted into easily transportable energy sources like liquid hydrocarbon fuels at the sites of methane production. The most important approach for the transformation of methane into liquid hydrocarbons is the well-established and already commercially proven route: [16] methane!syngas!methanol!gasoline, based on the methanol-to-gasoline (MTG) process developed by Mobil. [16][17][18] In 1985, Mobil successfully operated a commercial plant in New Zealand for MTG conversions. However, its operation had to be discontinued as a result of unfavorable process economics. [18][19][20] The cost of the syngas production step (by steam reforming) is about twice the cost of the MTG production step.The MTG process could become economically viable if it were possible to convert a significant portion of the methane into gasoline without the intermediate steps of conversion into syngas and methanol. Herein, we show that this very difficult goal can be met through the nonoxidative activation of methane and its simultaneous conversion with methanol into gasoline-range hydrocarbons over bifunctional Ga-, In-, Zn-, and/or Mo-modified ZSM-5 type zeolites that have both dehydrogenation and acid functions. We also show that the amount of methane converted can be equimolar to the amount of methanol converted in this novel process, depend-

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“…The operating conditions pose a second problem-how to translate the performance obtained in the laboratory to an affordable engineering solution at large scale. Also here a large number of solutions have been proposed, of which none has seen a successful implementation at commercial scale to date [7].…”

Section: General Perspectivementioning

confidence: 99%

Oxidative Coupling of Methane in Small Scale Parallel Reactors

Ras

Gómez‐Quero

2014

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In this work the testing of high temperature reactions in small scale parallel reactors is explored using the oxidative coupling of methane as an example. The advantages of small scale reactors for this very exothermic and complex reaction are discussed. The data generated in this study is explored making use of response surface models derived from statistically designed experiments. Methane conversion has been explored over a Mn-promoted Na 2 WO 4 /SiO 2 catalyst over the temperature range 755-875°C, pressure range 0.2-8.4 barg and GHSV range 4,000-36,000 h -1 using air as oxidant. Methane to oxygen stoichiometries of 4-8 have been explored. The highest C2 yield (16 %) is obtained at at low pressure.

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Catalytic oxidative coupling of methane—reaction engineering aspects and process schemes

Cited by 123 publications

References 58 publications

Structure sensitivity of the oxidative activation of methane over MgO model catalysts: I. Kinetic study

Structure sensitivity of the oxidative activation of methane over MgO model catalysts: I. Kinetic study

Simultaneous Conversion of Methane and Methanol into Gasoline over Bifunctional Ga‐, Zn‐, In‐, and/or Mo‐Modified ZSM‐5 Zeolites

Oxidative Coupling of Methane in Small Scale Parallel Reactors

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