Oxidative coupling of methane: An inherent limit to selectivity?

Labinger, Jay A.

doi:10.1007/bf00766166

Cited by 125 publications

(99 citation statements)

References 12 publications

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“…As Labinger pointed out 58) , formation of C3 and higher hydrocarbons was one of the major contributions to the reduced maximum attainable yield and was confirmed with the extended model including propylene, which predicts an additional loss of product yield at high conversions 66) . The depletion of O2 also causes a decrease in the rates of the catalytic pathways (including OH radical formation) and an increase in gas-phase combustion, leading to much lower selectivity.…”

Section: Mechanistic Aspects Of the Ocm Catalystsupporting

confidence: 53%

Catalytic Conversion of Methane: Carbon Dioxide Reforming and Oxidative Coupling

Takanabe

2012

J. Jpn. Petrol. Inst.

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Natural gas conversion remains one of the essential technologies for current energy needs. This review focuses on the mechanistic aspects of the development of efficient and durable catalysts for two reactions, carbon dioxide reforming and the oxidative coupling of methane. These two reactions have tremendous technological significance for practical application in industry. An understanding of the fundamental aspects and reaction mechanisms of the catalytic reactions reviewed in this study would support the design of industrial catalysts. CO2 reforming of methane utilizes CO2, which is often stored in large quantities, to convert as a reactant. Strategies to eliminate carbon deposition, which is the major problem associated with this reaction, are discussed. The oxidative coupling of methane directly produces ethylene in one reactor through a slightly exothermic reaction, potentially minimizing the capital cost of the natural gas conversion process. The focus of discussion in this review will be on the attainable yield of C2 products by rigorous kinetic analyses.

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Section: Mechanistic Aspects Of the Ocm Catalystsupporting

confidence: 53%

Catalytic Conversion of Methane: Carbon Dioxide Reforming and Oxidative Coupling

Takanabe

2012

J. Jpn. Petrol. Inst.

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“…The kinetic analysis of the experiments that use a Na 2 WO 4 /SiO 2 catalyst is consistent with the quasi‐equilibrated OH radical formation, which preferentially abstracts hydrogen from CH 4 over C 2 H 4 . The OCM reactions at high pressures remain a challenge because the carbon growth reactions are generally second order with respect to the hydrocarbon or relevant radical concentrations (Scheme ) 3g. The formation of higher hydrocarbons, the concentrations of which increase with high CH 4 conversion, leads to reduced C 2 yields because of their high rates of oxidation to CO x 3g.…”

Section: Resultsmentioning

confidence: 99%

Methane Coupling Reaction in an Oxy‐Steam Stream through an OH Radical Pathway by using Supported Alkali Metal Catalysts

Yin

Nourdine

et al. 2014

ChemCatChem

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A universal reaction mechanism involved in the oxidative coupling of methane (OCM) is demonstrated under oxy‐steam conditions using alkali‐metal‐based catalysts. Rigorous kinetic measurements indicated a reaction mechanism that is consistent with OH radical formation from a H2O–O2 reaction followed by CH activation in CH4 with an OH radical. Thus, the presence of water enhances both the CH4 conversion rate and the C2 selectivity. This OH radical pathway that is selective for the OCM was observed for the catalyst without Mn, which suggests clearly that Mn is not the essential component in a selective OCM catalyst. The experiments with different catalyst compositions revealed that the OH.‐mediated pathway proceeded in the presence of catalysts with different alkali metals (Na, K) and different oxo anions (W, Mo). This difference in catalytic activity for OH radical generation accounts for the different OCM selectivities. As a result, a high C2 yield is achievable by using Na2WO4/SiO2, which catalyzes the OH.‐mediated pathway selectively.

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“…These data indicate that C 2 selectivity (C 2 H 4 þ C 2 H 6 ) decreases with increasing CH 4 conversion resulting in a virtual one pass yield limit between 25 and 30 %. Indeed an inherent yield barrier of about 30 % was predicted by Labinger already in 1988 [60] based on kinetic arguments that radical HÁ abstraction is insensitive to the nature of the hydrocarbon molecule. Hence, not only CH 4 but also the coupling products C 2 H 6 and C 2 H 4 are activated on the catalyst leading to decreasing selectivity at increasing conversion.…”

Section: Ocm With Dioxygenmentioning

confidence: 97%

Methane Activation by Heterogeneous Catalysis

2014

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Methane activation by heterogeneous catalysis will play a key role to secure the supply of energy, chemicals and fuels in the future. Methane is the main constituent of natural gas and biogas and it is also found in crystalline hydrates at the continental slopes of many oceans and in permafrost areas. In view of this vast reserves and resources, the use of methane as chemical feedstock has to be intensified. The present review presents recent results and developments in heterogeneous catalytic methane conversion to synthesis gas, hydrogen cyanide, ethylene, methanol, formaldehyde, methyl chloride, methyl bromide and aromatics. After presenting recent estimates of methane reserves and resources the physico-chemical challenges of methane activation are discussed. Subsequent to this recent results in methane conversion to synthesis gas by steam reforming, dry reforming, autothermal reforming and catalytic partial oxidation are presented. The high temperature methane conversion to hydrogen cyanide via the BMA-process and the Andrussow-process is considered as well. The second part of this review focuses on one-step conversion of methane into chemicals. This includes the oxidative coupling of methane to ethylene mediated by oxygen and sulfur, the direct oxidation of methane to formaldehyde and methanol, the halogenation and oxyhalogenation of methane to methyl chloride and methyl bromide and finally the non-oxidative methane aromatization to benzene and related aromates. Opportunities and limits of the various activation strategies are discussed.

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Oxidative coupling of methane: An inherent limit to selectivity?

Cited by 125 publications

References 12 publications

Catalytic Conversion of Methane: Carbon Dioxide Reforming and Oxidative Coupling

Catalytic Conversion of Methane: Carbon Dioxide Reforming and Oxidative Coupling

Methane Coupling Reaction in an Oxy‐Steam Stream through an OH Radical Pathway by using Supported Alkali Metal Catalysts

Methane Activation by Heterogeneous Catalysis

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