The catalytic oxidation of methane to carbon monoxide and hydrogen

Prettre, Marcel; Eichner, C.; Perrin, Monique

doi:10.1039/tf946420335b

Cited by 267 publications

(117 citation statements)

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“…Prettre et al (1) were among the first to report formation of synthesis gas by catalytic conversion of CH 4 /O 2 mixtures at a stoichiometric feed ratio, i.e., a methane to oxygen feed molar ratio of 2, over 10 wt% refractory supported Ni at temperatures in the range of 973 to 1173 K. Thermodynamic equilibrium was achieved under all conditions studied, corresponding to the catalyst bed exit temperature. The reaction was reported to occur in two stages.…”

Section: Introductionmentioning

confidence: 92%

The Reaction Mechanism of the Partial Oxidation of Methane to Synthesis Gas: A Transient Kinetic Study over Rhodium and a Comparison with Platinum

Mallens

Hoebink

Marin

1997

Journal of Catalysis

146

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. M. M. (1997). The reaction mechanism of the partial oxidation of methane to synthesis gas: a transient kinetic study over rhodium and a comparison with platinum. Journal of Catalysis, 167(1), 43-56. DOI: 10.100643-56. DOI: 10. /jcat.199743-56. DOI: 10. .1533 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. The partial oxidation of methane to synthesis gas over rhodium sponge has been investigated by admitting pulses of pure methane and pure oxygen as well as mixtures of methane and oxygen to rhodium sponge at temperatures from 873 to 1023 K. Moreover, pulses of oxygen followed by methane and vice versa as well as pulses of mixtures of methane and labelled oxygen were applied to study the role of chemisorbed oxygen and incorporated oxygen in the reaction mechanism. The decomposition of methane on reduced rhodium results in the formation of carbon and hydrogen adatoms. During the interaction of pure dioxygen with rhodium the catalyst is almost completely oxidized to Rh 2 O 3 . In addition to rhodium oxide, oxygen is also present in the form of chemisorbed oxygen species. During the simultaneous interaction of methane and dioxygen at a stoichiometric feed ratio and a temperature of 973 K only 0.4 wt% Rh 2 O 3 is present. The chemisorbed oxygen species are completely desorbed after 2 s. A Mars-Van Krevelen mechanism is postulated: methane reduces the rhodium oxide, which is reoxidized by dioxygen. Synthesis gas is produced as primary product. Hydrogen is formed via the associative desorption of two hydrogen adatoms from reduced rhodium and the reaction between carbon adatoms and oxygen present as rhodium oxide results in the formation of carbon monoxide. The consecutive oxidation of CO and H 2 proceeds via both chemisorbed oxygen and oxygen present as rhodium oxide. Continuous flow experiments were performed to compare rhodium and platinum. When compared to platinum, rhodium shows a higher conversion to methane at a comparable temperature and also a higher selectivity to both CO and H 2 , the difference for CO being most pronounced. The observed differences in methane conversion and selectivities for the two catalysts are ascribed to the higher activation energy for methane decomposition on platinum compared to rhodium. An additional explanation for the difference in H 2 selectivit...

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Section: Introductionmentioning

confidence: 92%

The Reaction Mechanism of the Partial Oxidation of Methane to Synthesis Gas: A Transient Kinetic Study over Rhodium and a Comparison with Platinum

Mallens

Hoebink

Marin

1997

Journal of Catalysis

146

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“…5,6 But, coke formation occurred on the metal catalysts at the stoichiometric CH 4 /O 2 ratio. Such undesirable carbon formation cannot be avoided by increasing the O 2 /CH 4 ratio or by increasing the operating temperature without also increasing the potential explosion hazards, separation problems, and decreased synthesis gas selectivities.…”

Section: Introductionmentioning

confidence: 95%

Partial Oxidation of Methane over Ni/SiO₂

Roh

Dong

Jun

et al. 2002

Bulletin of the Korean Chemical Society

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Ni catalyst (Ni: 15 wt%) supported on precalcined SiO2 has been investigated in reforming reactions of methane to synthesis gas. The catalyst exhibited fairly good activity and stability in partial oxidation of methane (POM), whereas it deactivated in steam reforming of methane (SRM). Pulse reaction results of CH4, O2, and CH4/O2 revealed that Ni/SiO2 has high capability to dissociate methane. The results also revealed that both CH4 and O2 are activated on the surface of metallic Ni, and then surface carbon species react with adsorbed oxygen to produce CO and CO2 depending on the bond strength of the oxygen species on the catalyst surface.

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“…In the literature of recent years, two mechanisms have been proposed to account for this reaction, which may be designated as the 'combustion and reforming reactions mechanism', CRR, and the 'direct partial oxidation mechanism', DPO. The CRR mechanism was first proposed by Prettre et al [7]. They observed that the temperature increased sharply at the inlet of the catalyst bed, and this was followed by a temperature drop in the downstream of the catalyst bed.…”

Section: Introductionmentioning

confidence: 96%

Mechanism for catalytic partial oxidation of methane to syngas over a Ni/Al2O3 catalyst

2002

Fuel and Energy Abstracts

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The mechanism of catalytic partial oxidation of methane to syngas (POM) over a Ni/␣-A1 2 O 3 catalyst was studied by using a pulse reactor and temperature-programmed surface reaction (TPSR) techniques. Over a reduced nickel catalyst (Ni 0 /A1 2 O 3 ), methane activation follows the dissociation mechanism; while on oxidic nickel catalysts (NiO/Al 2 O 3 ), methane is first oxidized to carbon dioxide and water, and simultaneously, NiO is reduced to Ni 0 . CH 4 dissociation occurs over Ni 0 active sites, generating hydrogen and surface C species. A transient process was observed during the CH 4 /O 2 reaction. The nickel valence was transformed from NiO to Ni 0 at a certain critical temperature and simultaneously, the reaction was transformed rapidly from the complete oxidation of methane to the partial oxidation of methane. It has been found that the POM reaction takes place over a thin layer of the catalyst bed. This reaction zone is nearly isothermal, over which almost 100% of oxygen and more than 90% of methane are converted. The temperature drop in the downstream of the catalyst bed does not imply that the steam or carbon dioxide reforming reaction occurs in the lower part of the bed. Ni 0 species constitute the active sites for the partial oxidation of methane to syngas. Both methane and oxygen are activated on Ni 0 sites, generating surface Ni· · · C and Ni δ+ · · · O δ− species. These two kinds of intermediates have been proposed to account for the mechanism of methane partial oxidation. The Ni δ+ · · · O δ− species over Ni 0 catalyst surface is considered to be a kind of weakly bounded, mobile oxygen species. The reaction between Ni δ+ · · · O δ− and Ni· · · C intermediates generate the primary product of CO. However, the presence of NiO over the catalyst surface significantly reduces the CO selectivity. Thus, the NiO species are not possible to be the intermediate for the POM reaction. The mechanism of partial oxidation of methane should follow the direct oxidation route.

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The catalytic oxidation of methane to carbon monoxide and hydrogen

Cited by 267 publications

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The Reaction Mechanism of the Partial Oxidation of Methane to Synthesis Gas: A Transient Kinetic Study over Rhodium and a Comparison with Platinum

The Reaction Mechanism of the Partial Oxidation of Methane to Synthesis Gas: A Transient Kinetic Study over Rhodium and a Comparison with Platinum

Partial Oxidation of Methane over Ni/SiO₂

Mechanism for catalytic partial oxidation of methane to syngas over a Ni/Al2O3 catalyst

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The catalytic oxidation of methane to carbon monoxide and hydrogen

Cited by 267 publications

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The Reaction Mechanism of the Partial Oxidation of Methane to Synthesis Gas: A Transient Kinetic Study over Rhodium and a Comparison with Platinum

The Reaction Mechanism of the Partial Oxidation of Methane to Synthesis Gas: A Transient Kinetic Study over Rhodium and a Comparison with Platinum

Partial Oxidation of Methane over Ni/SiO2

Mechanism for catalytic partial oxidation of methane to syngas over a Ni/Al2O3 catalyst

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Partial Oxidation of Methane over Ni/SiO₂