A DFT Study of CH<i><sub>x</sub></i> Chemisorption and Transition States for C−H Activation on the Ru(112̄0) Surface

Ciobica, IM Ionel; Santen, van Ra Rutger

doi:10.1021/jp013210m

Cited by 70 publications

(57 citation statements)

References 26 publications

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“…Our activation energies for the reactions R.1, R.3, R.6, and R.10dehydrogenation reactions in methaneagree well with previous first-principles results 28 (Table 1).…”

Section: ■ Resultssupporting

confidence: 90%

First-Principles Investigation of C–H Bond Scission and Formation Reactions in Ethane, Ethene, and Ethyne Adsorbed on Ru(0001)

2014

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We have studied all possible elementary reactions (including isomerization reactions) involved in the interaction of CH 4 (methane), CH 3 CH 3 (ethane), CH 2 CH 2 (ethene), and CHCH (ethyne) with the Ru(0001) surface using density functional theory based first-principles calculations. Site preference and adsorption energies for all the reaction intermediates and activation energies for the elementary reactions are calculated. From the calculated adsorption and activation energies, we find that dehydrogenation of the adsorbates is thermodynamically favored in agreement with experiments. Dehydrogenation of CH (methylidyne) is the most difficult in the dehydrogenation of CH 4 (methane). CH 3 CH 3 (ethane), CH 2 CH 2 (ethene), and CHCH (ethyne) dehydrogenate through the CH 3 C (ethylidyne) intermediate. Of the five possible pathways for the production of CH 3 C (ethylidyne), the CH 2 CH (ethenyl)−CH 2 C (ethenylidene) pathway is the most dominant. In the case of ethene, the ethynyl−ethenylidene pathway is also the dominant pathway on Pt(111). Comparison of α and β-C−H bond scission reactions, important for the Fischer−Tropsch process, shows that alkenes should be the major products compared to the formation of alkynes. Dehydrogenation becomes slightly favorable at lower coverages of the hydrocarbon fragments while hydrogenation becomes slightly unfavorable. In addition to resolving the dominant pathways during decomposition of the above hydrocarbons, the activation energies calculated in this paper can also be used in the modeling of processes that involve the considered elementary reactions at longer length and time scales.

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“…Our activation energies for the reactions R.1, R.3, R.6, and R.10dehydrogenation reactions in methaneagree well with previous first-principles results 28 (Table 1).…”

Section: ■ Resultssupporting

confidence: 90%

First-Principles Investigation of C–H Bond Scission and Formation Reactions in Ethane, Ethene, and Ethyne Adsorbed on Ru(0001)

2014

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“…They concluded that ethylene should be formed through dehydrogenation of ethane and not by coupling of methane. Ciobica et al 19 calculated that on Ru (1120), the most stable species is CH 2 * and that the intermediates CH x (1 < x < 3) are more stable when adsorbed on bridged sites, while C species are preferentially adsorbed on top sites.…”

Section: Discussionmentioning

confidence: 99%

Activation of Methane on NiO Nanoparticles with Different Morphologies

Martins¹,

Schmal²

2014

Journal of the Brazilian Chemical Society

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Superfícies nanoestruturadas podem ser definidas como substratos tendo como principal característica dimensões na faixa de 1-100 nm. O recente interesse nestes sistemas é baseado no fato de que novas e interessantes propriedade (catalíticas, magnéticas, ferroelétricas, mecânicas, óticas e eletrônicas) são desenvolvidas como resultado da redução da dimensão destes substratos. Neste trabalho descreve-se a decomposição catalítica do metano em hidrogênio e nanofilamentos de carbono em catalisadores não suportados de Ni preparados por metodologias distintas. Catalisador de Ni suportado em zircônia foi usado para comparação dos resultados. Para os catalisadores não suportados, observou-se forte dependência da atividade do catalisador com o tamanho da partícula do óxido precursor e sua morfologia. Apesar de todos terem apresentado dimensões na faixa de nanopartículas, somente os preparados usando etileno glicol, NiEG, e rota hidrotérmica, NiHT, exibiram a mesma performance que o catalisador suportado (atividade e estabilidade), 25NiZ. O catalisador sintetizado em presença de dimetilglioxima, NiDMG, foi o menos ativo e desativou com o tempo em operação. Nanostructured surfaces can be defined as substrates in which the typical features have dimensions in the range of 1-100 nm. The recent focus of interest in these systems is based on the fact that interesting novel properties (catalytic, magnetic, ferroelectric, mechanical, optical and electronic) are developed as a result of the dimension reductions of these substrates. This paper describes the catalytic methane decomposition into hydrogen and carbon nanofilaments on unsupported Ni catalysts prepared from different methodologies, with controlled particle size and morphologies. Ni catalyst supported on zirconia was also used for performance comparison. For the unsupported catalysts, it was observed strong dependency of catalyst activities with particle size of nickel oxide precursors and their morphologies. Although all of them presented crystallite sizes with nanometric dimensions, only those prepared with ethylene glycol, NiEG, and by hydrothermal condition, NiHT, exhibited the same performance as the supported catalyst (activity and stability), 25NiZ. Catalyst synthesized in the presence of dimethylglyoxime, NiDMG, was less active and deactivated with time on stream.

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“…The same effect has been found for a number of other molecules. [35][36][37][38][39][40][41] Such effects are clearly important in determining the activity of a catalyst. For reactions where steps have a high reactivity, the density of such sites on the supported nanoparticle catalysts is a crucial parameter.…”

Section: The Geometrical and Electronic Factor In Catalysismentioning

confidence: 99%

A molecular view of heterogeneous catalysis

Christensen

Nørskov

2008

The Journal of Chemical Physics

120

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The establishment of a molecular view of heterogeneous catalysis has been hampered for a number of reasons. There are, however, recent developments, which show that we are now on the way towards reaching a molecular-scale picture of the way solids work as catalysts. By a combination of new theoretical methods, detailed experiments on model systems, and synthesis and in situ characterization of nano-structured catalysts, we are witnessing the first examples of complete atomic-scale insight into the structure and mechanism of surface-catalyzed reactions. This insight has already proven its value by enabling a rational design of new catalysts. We illustrate this important development in heterogeneous catalysis by highlighting recent examples of catalyst systems for which it has been possible to achieve such a detailed understanding. In particular, we emphasize examples where this progress has made it possible to propose entirely new catalysts, which have then been proven experimentally to exhibit improved performance in terms of catalytic activity or selectivity.

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A DFT Study of CH_x Chemisorption and Transition States for C−H Activation on the Ru(112̄0) Surface

Cited by 70 publications

References 26 publications

First-Principles Investigation of C–H Bond Scission and Formation Reactions in Ethane, Ethene, and Ethyne Adsorbed on Ru(0001)

First-Principles Investigation of C–H Bond Scission and Formation Reactions in Ethane, Ethene, and Ethyne Adsorbed on Ru(0001)

Activation of Methane on NiO Nanoparticles with Different Morphologies

A molecular view of heterogeneous catalysis

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A DFT Study of CHx Chemisorption and Transition States for C−H Activation on the Ru(112̄0) Surface

Cited by 70 publications

References 26 publications

First-Principles Investigation of C–H Bond Scission and Formation Reactions in Ethane, Ethene, and Ethyne Adsorbed on Ru(0001)

First-Principles Investigation of C–H Bond Scission and Formation Reactions in Ethane, Ethene, and Ethyne Adsorbed on Ru(0001)

Activation of Methane on NiO Nanoparticles with Different Morphologies

A molecular view of heterogeneous catalysis

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A DFT Study of CH_x Chemisorption and Transition States for C−H Activation on the Ru(112̄0) Surface