Modelling excited species and their role on kinetic pathways in the non-oxidative coupling of methane by dielectric barrier discharge

Maitre, Pierre-André; Bieniek, M. S.; Kechagiopoulos, Panagiotis N.

doi:10.1016/j.ces.2020.116399

Cited by 17 publications

(29 citation statements)

References 90 publications

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“…• formation, whereas vibrationally excited methane does not contribute significantly to its formation. 59 The methane coupling reaction to form C 2 H 6 occurs primarily by the recombination of CH , and so on). Unselective formation of heavier hydrocarbons is one of the major challenges in plasma-driven NCM, which limits the final C 2 selectivity and yield.…”

Section: Discussionmentioning

confidence: 97%

“…CH 4 activation occurs by excitation of methane by electrons in the plasma to form vibrationally or electronically excited molecules that get converted to CH 3 • free radicals by self-dissociation or collision, recombination with electrons and other species. Simulation and modeling studies indicate that the predissociation of electronically excited methane species is the primary route of CH 3 • formation, whereas vibrationally excited methane does not contribute significantly to its formation . The methane coupling reaction to form C 2 H 6 occurs primarily by the recombination of CH 3 • free radicals.…”

Section: Discussionmentioning

confidence: 99%

“…In plasma reactors, the reaction pathway followed for NCM is quite different, and the reaction mixture contains numerous species including molecules, metastable (vibrationally or electronically excited) species, free radicals, and ions. 59 CH 4 activation occurs by excitation of methane by electrons in the plasma to form vibrationally or electronically excited molecules that get converted to CH 3 • free radicals by self-dissociation or collision, recombination with electrons and other species. Simulation and modeling studies indicate that the predissociation of electronically excited methane species is the primary route of CH 3…”

Section: Discussionmentioning

confidence: 99%

“…As stated above, vibrationally and electronically excited CH 4 molecules are generated with elevated internal energy in the plasma discharge. It has been predicted by modeling studies that vibrational excitation of methane and the product molecules consumes more than 50% of the total energy provided in NCM under DBD plasma; however, they contribute very little (<1%) to the product formation in the plasma reactor. We believe that in the integrated plasma-catalytic system, these vibrationally excited methane species can adsorb on the Pt sites of the catalyst, where they can undergo dissociation to form CH 3 – x .…”

Section: Discussionmentioning

confidence: 99%

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Nonoxidative Coupling of Methane over Ceria-Supported Single-Atom Pt Catalysts in DBD Plasma

Liu

Das

Zhang

et al. 2022

ACS Appl. Mater. Interfaces

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Plasma-catalytic direct nonoxidative coupling of methane (NCM) into C2 hydrocarbons was investigated over ceria-supported atomically dispersed Pt (Pt/CeO2-SAC) and nanoparticle Pt (Pt/CeO2-NP) catalysts in dielectric barrier discharge (DBD) plasma. Nonthermal plasma facilitated C–H bond dissociation in CH4 at low temperatures (<150 °C) and atmospheric pressure. The presence of Pt/CeO2 catalysts in plasma further enhanced CH4 conversion and C2 hydrocarbon selectivity by enabling the conversion of vibrationally excited methane species with high internal energy on active Pt sites. Noticeably, the Pt/CeO2-SAC catalyst displayed a more remarkable performance, with a CH4 conversion of 39% and a C2 selectivity of 54% at 54 W. The enhanced CH4 conversion was attributed to abundant coordinatively unsaturated Pt sites in Pt/CeO2-SAC, which were more active for C–H bond scission. Meanwhile, isolated Pt atoms in Pt/CeO2-SAC promoted C2 hydrocarbon formation by hindering the unselective formation of coke from deep dehydrogenation of CH x • intermediates and higher hydrocarbons from oligomerization reactions.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Nonoxidative Coupling of Methane over Ceria-Supported Single-Atom Pt Catalysts in DBD Plasma

Liu

Das

Zhang

et al. 2022

ACS Appl. Mater. Interfaces

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“…The sticking rates of ions and neutral species follow the same formalism as in Maitre et al L α , stick = ψ α 0.25em k b T e M α n α L β , stick = s β 0.25em ψ β normals 0.25em 3 k b T 0 M β n β where M (kg) is the mass of the species considered. The sticking probabilities, s β (−), considered in Maitre et al are also used in this work, while for ions a value of 1 is assumed.…”

Section: Methodsmentioning

confidence: 99%

Plasma-Catalysis of Nonoxidative Methane Coupling: A Dynamic Investigation of Plasma and Surface Microkinetics over Ni(111)

2022

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A heterogeneous catalytic microkinetic model is developed and implemented in a zero-dimensional (0D) plasma model for the dynamic study of methane nonoxidative coupling over Ni(111) at residence times and power densities consistent with experimental reactors. The microkinetic model is thermodynamically consistent and is parameterized based on the heats of chemisorption of surface species on Ni(111). The surface network explicitly accounts for the interactions of plasma species, namely, molecules, radicals, and vibrationally excited states, with the catalyst active sites via adsorption and Eley−Rideal reactions. The Fridman−Macheret model is used to describe the enhancement of the rate of the dissociative adsorption of vibrationally excited CH 4 , H 2 , and C 2 H 6 . In combination with a previously developed detailed kinetic scheme for nonthermal methane plasma, 0D simulation results bring insights into the complex dynamic interactions between the plasma phase and the catalyst during methane nonoxidative coupling. Differential turnover frequencies achieved by plasmacatalysis are higher than those of equivalent plasma-only and catalysis-only simulations combined; however, this performance can only be sustained momentarily. Hydrogen produced from dehydrogenation of ethane via electron collisions within the plasma is found to quickly saturate the surface and even promote the conversion of surface CH 3 * back to methane.

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Modelling the dynamics of hydrogen synthesis from methane in nanosecond‐pulsed plasmas

Morais,

Bogaerts

2023

Plasma Processes & Polymers

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A chemical kinetics model was developed to characterise the gas‐phase dynamics of H2 production in nanosecond‐pulsed CH4 plasmas. Pulsed behaviour was observed in the calculated electric field, electron temperature and species densities at all pressures. The model agrees reasonably with experimental results, showing CH4 conversion at 30% and C2H2 and H2 as major products. The underlying mechanisms in CH4 dissociation and H2 formation were analysed, highlighting the large contribution of vibrationally excited CH4 and H2 to coupling energy from the plasma into gas‐phase heating, and revealing that H2 synthesis is not affected by applied pressure, with selectivity remaining unchanged at ~42% in the 1–5 bar range.

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Modelling excited species and their role on kinetic pathways in the non-oxidative coupling of methane by dielectric barrier discharge

Cited by 17 publications

References 90 publications

Nonoxidative Coupling of Methane over Ceria-Supported Single-Atom Pt Catalysts in DBD Plasma

Nonoxidative Coupling of Methane over Ceria-Supported Single-Atom Pt Catalysts in DBD Plasma

Plasma-Catalysis of Nonoxidative Methane Coupling: A Dynamic Investigation of Plasma and Surface Microkinetics over Ni(111)

Modelling the dynamics of hydrogen synthesis from methane in nanosecond‐pulsed plasmas

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