Synthesis gas formation by direct oxidation of methane over Rh monoliths

Hickman, Daniel A.; Haupfear, E. A.; Schmidt, L.D.

doi:10.1007/bf00766145

Cited by 299 publications

(132 citation statements)

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“…However, Dissanayake et al (14) report that a difference between the measured and the actual reaction temperature also provides an explanation for the observed difference in selectivities. Formation of CO and H 2 as primary reaction products in the partial oxidation of methane is reported by Hickman and Schmidt (15)(16)(17) applying adiabatically operated monoliths containing a platinum or rhodium catalyst at outlet temperatures around 1300 K and residence times between 10 −4 and 10 −2 s. Simulations carried out on the basis of a model consisting of 19 elementary reaction steps provided a theoretical basis for this observation (18).…”

Section: Introductionmentioning

confidence: 79%

“…The number of molecules admitted per single pulse was in the range of 10 15 -10 16 , resulting in an average total pressure of 100 Pa above the catalyst surface during 100 ms. Gas phase reactions can be neglected under these conditions. In a single pulse the ratio of admitted methane as well as oxygen molecules to the theoretical number of surface rhodium atoms was always below 0.05.…”

Section: Equipment and Proceduresmentioning

confidence: 99%

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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

Mallens

Hoebink

Marin

1997

Journal of Catalysis

148

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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: 79%

Section: Equipment and Proceduresmentioning

confidence: 99%

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

148

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“…(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11) can principally be used in the numerical simulation of laminar as well as turbulent flow fields; the so-called Direct Numerical Simulations, DNS. In practice, however, the solution of the Navier-Stokes equations for turbulent flows demands a prohibitive amount of computational time due to the huge number of grid points needed to resolve the small scales of turbulence.…”

Section: Modeling Of the Interactions 275mentioning

confidence: 99%

“…Catalytic monoliths can serve as an example. They are frequently used for the reduction of pollutant emissions from automobiles [1], selective oxidation [2][3][4] and reforming of hydrocarbons [5,6], and combustion of natural gas [7][8][9]. Figure 1 illustrates the physics and chemistry in a catalytic combustion monolith that glows at a temperature of about 1,300 K due to the exothermic oxidation reactions.…”

Section: Introductionmentioning

confidence: 99%

Modeling of the Interactions Between Catalytic Surfaces and Gas-Phase

Deutschmann

2014

Catal Lett

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The catalytic surface interacts with the gasphase by a variety of chemical and physical processes. Hence, optimization of design and operation conditions of catalytic reactors do not only require the understanding of the catalytic reaction sequence but also its coupling with mass and heat transport and potential homogeneous reactions. The chemical, thermal, and mass-transport interactions between the catalytic surface and the gas-phase are discussed in terms of the individual and combined interactions. The state-of-the-art modelling of reactive flows and its coupling with the catalytic surface is summarized. The interactions are illustrated by a number of examples such as reforming of hydrocarbons, catalytic combustion, exhaust-gas after-treatment, each focusing on a special aspect of catalyst-gas interactions. The potentials and limitations of the numerical simulations will be discussed including experimental techniques for model validation.

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“…Synthesis gas is one of the most imp,ortant intermediate products in the chemical industry. Rh-catalyzed direct CPO starts when a gas mixture of methane and oxygen is heated up to 600 "C: The exothermic CP0,reaction causes the temperature to go up as high as 1000 "C [2]. Initial heating of the gas mixture takes place with Pt heating ,filaments, located on a thin membrane (figure '1).…”

Section: Introductionmentioning

confidence: 99%

A new technique for accurately defined deposition of catalyst thin films in deep flow channels of high-temperature gas microreactors

Tiggelaar

Berenschot

Oosterbroek

et al.

TRANSDUCERS '03. 12th International Conference on Solid-State Sensors, Actuators and Microsystems. Digest of Technical Papers (

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By using microreactors fabricated with silicon microtechnology, heterogeneous catalyzed gas-phase reactions can be studied which are difficult to control because of their exothermic nature, are explosive or use toxichazardous gases. In this type of microreactors, catalytic materials like rhodium or platinum are deposited on a thin membrane in deep trenches. Conventional techniques, like lift-off lithography, cannot be used in deep trenches and deposition through flat shadow masks does not yield well-defined regions of catalyst. For well-controlled deposition of a catalytic thin film on a membrane located in a deep trench, a technique is developed using sputter deposition with a 3-dimensionally shaped 'self-aligning' shadow mask. INTRODUCTIONDue to the small dimensions of the gas flow channels in silicon-technology based microreactors (high-surface-tovolume ratios) and integration of functional elements like heaters and sensors, it becomes possible to control hightemperature catalytic partial oxidation reactions and study

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Synthesis gas formation by direct oxidation of methane over Rh monoliths

Cited by 299 publications

References 13 publications

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

Modeling of the Interactions Between Catalytic Surfaces and Gas-Phase

A new technique for accurately defined deposition of catalyst thin films in deep flow channels of high-temperature gas microreactors

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