Oxidative coupling of methane: Mechanism and kinetics

Lomonosov, V. I.; Sinev, M. Yu.

doi:10.1134/s0023158416050128

Cited by 79 publications

(71 citation statements)

References 177 publications

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“…We suggest that CH 4 is activated in a process that is similar to that suggested to occur during the OCM. During the OCM process, it is well accepted that the initial step in the reaction is the reaction of CH 4 with the catalyst forming gas phase CH 3 free radicals . The formation of CH 3 radicals in the OCM process has been confirmed by Luo et al .…”

Section: Resultsmentioning

confidence: 84%

“…During the OCM process, it is well accepted that the initial step in the reaction is the reaction of CH 4 with the catalyst forming gas phase CH 3 free radicals. 26,27,44 The formation of CH 3 radicals in the OCM process has been confirmed by Luo et al with synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) over Li/MgO catalyst. 45 In the presence of an enhanced concentration of CH 3 radicals, higher yields of VDF are achieved via Reaction (1).…”

Section: Effect Of Lanthanum Catalyst On the Combination Of Ocm And Cmentioning

confidence: 81%

“…At relatively low temperatures (such as 700°C), with the presence of LaOF catalyst and O 2 , CH 4 is activated catalytically rather than with chain reactions. According to the mechanism of OCM reactions, CH 4 is probably activated via the following reactions:

{[O]}_{normalS} + C {normalH}_{4} \to C {normalH}_{3} + {[OH]}_{normalS}

\begin{matrix} true \\ right {false[{normalO}^{2 -} false]}_{S} + normalC H_{4} \to normalC H_{3} + {false[{O_{2}}^{- • • •} {normalH}^{+} false]}_{S} + {false[normalC {H_{3}}^{-} false]}_{s} \end{matrix}

{[C {normalH}_{3}^{-}]}_{normals} \to C {normalH}_{3} + e^{-}

Two pathways of activation of CH 4 are therefore suggested. First, CH 4 reacts directly with active oxygen, producing CH 3 (Reaction ).…”

Section: Discussionmentioning

confidence: 94%

“…For many years, OCM has been intensively investigated for the conversion of CH 4 to C 2 H 6 and C 2 H 4 . It is well accepted that CH 3 is the initial reaction product formed during the OCM process . Consequently, the coupling of CH 3 radicals leads to the production of C 2 H 6 and C 2 H 4 .…”

Section: Introductionmentioning

confidence: 99%

“…[22][23][24] It is well accepted that CH 3 is the initial reaction product formed during the OCM process. [25][26][27] Consequently, the coupling of CH 3 radicals leads to the production of C 2 H 6 and C 2 H 4 . During the gas-phase reaction of CH 4 and CHF 3 it was suggested that CHF 3 firstly decomposes into CF 2 and while CH 4 is activated via a series of free radical reactions, yielding CH 3 .…”

Section: Introductionmentioning

confidence: 99%

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Catalytic coupling of CH₄ with CHF₃ for the synthesis of VDF over LaOF catalyst

et al. 2018

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The oxidative coupling of methane (OCM) with CHF3 facilitates the synthesis of vinylidene fluoride (VDF). The aim is to utilize CHF3, which is otherwise considered a waste with a very high global warming potential. This study focuses on the effect of a LaOF catalyst on OCM occurring in the presence of CHF3, which engenders a promoting effect of O2 on CH4 activation. It examines the structural and phase changes of the lanthanum catalyst during the reaction and then speculates on the reaction mechanism. In combining OCM with CHF3, both the conversion of CH4 and the formation rate of VDF are almost tripled at 700°C. However, at higher temperatures, gas‐phase reactions play a dominating role in the conversion of CH4 and LaOF catalyst plays a very minor role in the reaction system at elevated temperatures. Irrespective of the reaction temperature, VDF is produced via the gas‐phase coupling of CH3 radicals with CF2. During pretreatment or during the reaction itself, La2O3 is fluorinated by CHF3 and HF, yielding the formation of surface LaOF and LaF3 species. LaF3 is a relatively inactive catalyst for CH4 conversion, whereas, in comparison LaOF appears to play a very important role in the activation of CH4 at low temperatures. The activation mechanism of CH4 at relatively low temperatures is similar with that postulated to occur during the OCM. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.

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Section: Resultsmentioning

confidence: 84%

Section: Effect Of Lanthanum Catalyst On the Combination Of Ocm And Cmentioning

confidence: 81%

{[O]}_{normalS} + C {normalH}_{4} \to C {normalH}_{3} + {[OH]}_{normalS}

\begin{matrix} true \\ right {false[{normalO}^{2 -} false]}_{S} + normalC H_{4} \to normalC H_{3} + {false[{O_{2}}^{- • • •} {normalH}^{+} false]}_{S} + {false[normalC {H_{3}}^{-} false]}_{s} \end{matrix}

{[C {normalH}_{3}^{-}]}_{normals} \to C {normalH}_{3} + e^{-}

Two pathways of activation of CH 4 are therefore suggested. First, CH 4 reacts directly with active oxygen, producing CH 3 (Reaction ).…”

Section: Discussionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Catalytic coupling of CH₄ with CHF₃ for the synthesis of VDF over LaOF catalyst

et al. 2018

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Kinetics and Mechanisms of Selected Reactions over Hydroxyapatite‐Based Catalysts

Ashik¹,

Halim²,

Asano³

et al. 2022

Design and Applications of Hydroxyapatite‐Based Catalysts

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Oxidative coupling of methane over strontium‐doped neodymium oxide: Parametric evaluations

et al. 2022

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Since its discovery in 1982, oxidative coupling of methane (OCM) has been considered one of the most promising approaches for the on-purpose synthesis of ethylene.The development of more selective catalysts is essential to improve process economics. In this work, undoped neodymium oxide as well as neodymium oxide doped with high (20%) and low (2.5%) levels of strontium were tested in a high-throughput fashion covering a wide range of operating conditions. The catalysts were shown to be able to achieve greater than 18% C 2 + yield. Space velocity was shown to play a significant role in C 2 + selectivity. For a methane to oxygen feed ratio of 3.5, selectivity increased with increasing space velocity, reaching a maximum of 62% at a methane conversion of 30% at an optimal space velocity of $250,000 ml/h/g. The difference in activity between the three samples was linked to the contribution of different oxygen centers.

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Oxidative coupling of methane: Mechanism and kinetics

Cited by 79 publications

References 177 publications

Catalytic coupling of CH₄ with CHF₃ for the synthesis of VDF over LaOF catalyst

Catalytic coupling of CH₄ with CHF₃ for the synthesis of VDF over LaOF catalyst

Kinetics and Mechanisms of Selected Reactions over Hydroxyapatite‐Based Catalysts

Oxidative coupling of methane over strontium‐doped neodymium oxide: Parametric evaluations

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Oxidative coupling of methane: Mechanism and kinetics

Cited by 79 publications

References 177 publications

Catalytic coupling of CH4 with CHF3 for the synthesis of VDF over LaOF catalyst

Catalytic coupling of CH4 with CHF3 for the synthesis of VDF over LaOF catalyst

Kinetics and Mechanisms of Selected Reactions over Hydroxyapatite‐Based Catalysts

Oxidative coupling of methane over strontium‐doped neodymium oxide: Parametric evaluations

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Catalytic coupling of CH₄ with CHF₃ for the synthesis of VDF over LaOF catalyst

Catalytic coupling of CH₄ with CHF₃ for the synthesis of VDF over LaOF catalyst