H2/D2 isotopic exchange: A tool to characterize complex hydrogen interaction with carbon-supported ruthenium catalysts

García-García, Francisco J.; Bion, Nicolas; Duprez, Daniel; Rodrı́guez-Ramos, I.; Guerrero-Ruı́z, A.

doi:10.1016/j.cattod.2015.03.014

Cited by 13 publications

(16 citation statements)

References 55 publications

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“…Electronegative promoters δ = +0.1 e instead destabilize the adsorbed intermediates, making it easier to desorb. This is broadly consistent with experiment: electropositive sodium promotes hydrogen–deuterium exchange, whereas electronegative chlorine disfavors H 2 adsorption…”

Section: Resultssupporting

confidence: 89%

“…In this reaction, physisorbed H 2 and D 2 molecules dissociate into adsorbed H and D, migrate over the cluster surface, and recombine to form HD. Experimentally, electropositive sodium is known to promote hydrogen–deuterium exchange over supported ruthenium, though local promoter effects inhibit H atom spillover to the catalyst support . Electronegative chlorine, in catalysts prepared from RuCl 3 , raises the activation energies for irreversible hydrogen adsorption onto alumina‐supported ruthenium catalysts…”

Section: Resultsmentioning

confidence: 99%

“…Experimentally, electropositive sodium is known to promote hydrogen-deuterium exchange over supported ruthenium, though local promoter effects inhibit H atom spillover to the catalyst support. [52] Electronegative chlorine, in catalysts prepared from RuCl 3 , raises the activation energies for irreversible hydrogen adsorption onto alumina-supported ruthenium catalysts. [53] Figure 3 shows our computed potential energy surfaces for the unpromoted catalyst.…”

Section: Promoter Effects On Hydrogen Scramblingmentioning

confidence: 99%

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Tunable model promoters in DFT simulations of catalysts

et al. 2019

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Promoter atoms can tune a catalyst's activity and selectivity by transferring charge to and from the active site. Rational design of promoted catalysts, using density functional theory calculations, is today limited by the need to simulate many catalyst and promoter configurations. We present a simple approximation that rapidly captures some trends in promoter effects, at a cost of complexity comparable with simulating unpromoted catalysts. Negative (positive) noninteger point charges introduced into the catalyst simulate how electropositive (electronegative) promoters might affect each predicted intermediate. Calculations return Sabatier plots, relating promoters' predicted efficacy to readily measured properties such as catalyst work functions. We illustrate our approach for two reactions associated with the Fischer–Tropsch process, hydrogen–deuterium scrambling, and carbon monoxide dissociation over ruthenium. Consistent with experiment, electropositive promoters are predicted to accelerate hydrogen scrambling and unassisted CO dissociation. Simulations also provide a new prediction: electronegative promoters accelerate hydrogen‐assisted CO dissociation over hydrogen‐precovered surfaces by stabilizing the initial CO adsorption. © 2019 Wiley Periodicals, Inc.

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Section: Resultssupporting

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Section: Promoter Effects On Hydrogen Scramblingmentioning

confidence: 99%

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Tunable model promoters in DFT simulations of catalysts

et al. 2019

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“…This is because the H 2 and D 2 easily dissociate on the metal surface and recombination of H and D atoms occurs at a rapid rate. The thermodynamic HD yield produced during the isotopic H 2 ‐D 2 exchange reaction at 0 °C for different H 2 ‐D 2 feed mixtures was reported by Garcia et al, who observed that the reaction is thermodynamically limited at this temperature: only a 65 mol% HD yield is produced for a H 2 ‐D 2 ratio equal to 1. Despite thermodynamic equilibrium limitations, the reaction has the advantage that even at low temperatures the kinetics are sufficiently rapid that a measurable conversion, even at low metal contents in the catalyst, can be obtained …”

Section: Resultsmentioning

confidence: 63%

“…Generally, two types of experiments have been investigated in the literature: (a) homoexchange reactions, denoted “equilibration,” when the adsorption‐desorption on the metal particle is rate‐limiting; and (b) heteroexchange reactions, denoted “isotopic exchange.” In homoexchange reactions, the two hydrogen isotopomers are in equilibrium at the catalyst surface. In most cases, this reaction is much faster on the metal than on the support.…”

Section: Introductionmentioning

confidence: 99%

Fischer‐Tropsch synthesis: Effect of solvent on the H₂‐D₂ isotopic exchange rate over an activated cobalt catalyst

et al. 2016

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The effect of solvent on the hydrogen-deuterium isotopic homomolecular exchange over a traditional Fischer-Tropsch cobalt catalyst (25 % Co/Al 2 O 3 ) was investigated using a plug flow reactor at two different reaction temperatures (room temperature (26 8C) and -20 8C) and at atmospheric pressure. In this study, three different solvents were tested, including n-pentane, n-hexadecane, and C-30 oil. The consumption of H 2 and D 2 is the same, and the concentration of the HD produced is twice the consumption of H 2 or D 2 at dry (without solvent) conditions. At room temperature and at -20 8C, conditions without solvent exhibited 100 mol% exchange with the formation of H 2 :HD:D 2 having a 1:2:1 ratio. For n-pentane solvent, the exchange rates were $97 and $80 mol% at 26 and À20 8C, respectively. For the n-hexadecane and C 30 oil solvents, the initial exchange rate was $50 mol%, with the exchange rate decreasing over time. The lower exchange rate with the n-hexadecane and C 30 oil solvents, and also n-pentane at -20 8C, is likely due primarily to the limited mobility of reactant molecules in the liquid-filled pores of the catalyst. Blocking or covering of the pores of the catalyst depends on the molecular mass and density of the solvent. No isotopic partitioning preference was observed at two different temperatures and various solvents for the active cobalt catalyst.

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Isotopic H/D exchange on graphenes. A combined experimental and theoretical study

Sastre

Forneli

Almăşan

et al. 2017

Applied Catalysis A: General

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Adsorption of H 2 /D 2 on graphene (G), graphene oxide (GO), single walled carbon nanotube (SWCNT), N-doped graphene [(N)G], and a sample of active carbon (C) has led to the detection of HD, indicating dissociative chemisorption of hydrogen on the surface of the material. The amount of HD detected follows the order G>SWCNT>GO~(N)G~C, G giving about five-fold higher H 2 /D 2 adsorption and HD exchange level than SWCNT and about tenfold larger values than that of the other samples. Quantum-chemistry calculations modeling a carbon atom vacancy on a G cluster estimates an activation barrier for H 2 dissociation of ca. 84 kJ/mol for a mechanism involving under coordinated carbon atoms at the defect site.

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H2/D2 isotopic exchange: A tool to characterize complex hydrogen interaction with carbon-supported ruthenium catalysts

Cited by 13 publications

References 55 publications

Tunable model promoters in DFT simulations of catalysts

Tunable model promoters in DFT simulations of catalysts

Fischer‐Tropsch synthesis: Effect of solvent on the H₂‐D₂ isotopic exchange rate over an activated cobalt catalyst

Isotopic H/D exchange on graphenes. A combined experimental and theoretical study

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H2/D2 isotopic exchange: A tool to characterize complex hydrogen interaction with carbon-supported ruthenium catalysts

Cited by 13 publications

References 55 publications

Tunable model promoters in DFT simulations of catalysts

Tunable model promoters in DFT simulations of catalysts

Fischer‐Tropsch synthesis: Effect of solvent on the H2‐D2 isotopic exchange rate over an activated cobalt catalyst

Isotopic H/D exchange on graphenes. A combined experimental and theoretical study

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Fischer‐Tropsch synthesis: Effect of solvent on the H₂‐D₂ isotopic exchange rate over an activated cobalt catalyst