Oxidation of Alumina-Supported Co and Co−Pd Model Catalysts for the Fischer−Tropsch Reaction

Nowitzki, Tobias; Carlsson, Anders; Martyanov, Oleg N.; Naschitzki, Matthias; Zielasek, Volkmar; Risse, Thomas; Schmal, Martín; Freund, Hans‐Joachim; Bäumer, Marcus

doi:10.1021/jp066796r

Cited by 36 publications

(27 citation statements)

References 59 publications

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“…For monometallic Co (1), carbon monoxide desorption is observed at % 530 K. This temperature is significantly higher than the desorption temperature of molecular CO from metallic or oxygen-treated particles, [37] clearly indicating that the removal of carbon is reaction-limited. Apparently, carbon monoxide leaves the surface immediately after its formation and is not oxidized further, as no carbon dioxide desorption is observed in this case.…”

Section: Resultsmentioning

confidence: 93%

“…Additionally, the influence of adsorbed oxygen or oxidic phases, for example, those generated by CÀO bond scission, on the methanol dehydrogenation is investigated in the case of Co, which is particularly prone to changes in surface chemistry by surface and subsurface oxygen species. [37] Finally, by comparing the results obtained under UHV conditions to the findings obtained in continuous-flow reactors under ambient conditions, [38] we demonstrate that the UHV studies are of high relevance for understanding the reactions on real catalyst surfaces.…”

Section: Introductionmentioning

confidence: 80%

“…Under UHV conditions, even small amounts of oxygen were reported to have a large impact on the adsorption behavior, at least for carbon monoxide, by significantly weakening the interaction between molecule and surface. [37] To explore the impact of oxygen on the dehydrogenation of methanol in the case of Co, pristine metallic particles were exposed to 50 L of oxygen at 300 K. As reported elsewhere, this amount is sufficient to generate a surface oxide species, which shifts the carbon monoxide desorption to temperatures below 250 K. [37] Unfortunately, desorption of molecular methanol takes place in the same temperature regime, so that a possible desorption of carbon monoxide generated by dehydrogenation might be hidden by the peak stemming from fragmentation of methanol in the mass spectrometer. Therefore, the surface was not saturated with methanol for this experiment to prevent desorption of molecular methanol in the TPD experiments.…”

Section: Carbon Monoxide Dissociation On Monometallic Comentioning

confidence: 99%

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UHV Studies of Methanol Decomposition on Mono‐ and Bimetallic CoPd Nanoparticles Supported on Thin Alumina Films

et al. 2008

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Bimetallic nanoparticles often turn out to be superior to the corresponding monometallic systems with respect to their catalytic properties. To study such effects for the methanol decomposition reaction, model catalysts were prepared by physical vapor deposition of Pd and Co under ultrahigh-vacuum (UHV) conditions. Monometallic Pd and Co particles as well as CoPd core-shell particles were generated on an epitaxial alumina film grown on NiAl(110). The interaction with methanol is examined by temperature-programmed desorption of methanol and carbon monoxide and by X-ray photoelectron spectroscopy. The decomposition of methanol proceeds in two reaction pathways independent of the particle composition: complete dehydrogenation towards carbon monoxide and hydrogen, and C--O bond scission yielding carbon deposits. Pd is the most active material studied here. The relative importance of the two channels varies for the different particle systems: on Pd dehydrogenation is preferred, whereas the C--O bond cleavage is more pronounced on Co. The bimetallic clusters show a moderate performance for both pathways. Carbon deposition poisons the model catalysts by blocking the adsorption sites for methoxide, which is the first intermediate product during methanol decomposition. In particular on Co, large amounts of carbon deposits can also be caused by dissociation of the final product of the dehydrogenation pathway, carbon monoxide. A comparison with the results of methanol decomposition on Co, Pd, and CoPd catalysts in continuous-flow reactors demonstrates that the findings of the present UHV study are relevant for catalytic performance under high-pressure conditions.

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Section: Resultsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 80%

Section: Carbon Monoxide Dissociation On Monometallic Comentioning

confidence: 99%

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UHV Studies of Methanol Decomposition on Mono‐ and Bimetallic CoPd Nanoparticles Supported on Thin Alumina Films

et al. 2008

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“…In Co-Pd alumina supported catalysts, the presence of cobalt core-palladium shell bimetallic particles was reported by Nowitzki et al [59] using a combination of several characterization techniques. The reactivity of these particles strongly depended on extent of coverage of cobalt core by palladium atoms.…”

Section: Formation Of Bimetallic Particlesmentioning

confidence: 89%

Promotion of Cobalt Fischer-Tropsch Catalysts with Noble Metals: a Review

Diehl¹,

Khodakov²

2008

Oil & Gas Science and Technology - Rev. IFP

163

109

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Résumé-Promotion par les métaux nobles de catalyseurs Fischer-Tropsch à base de cobalt : une revue -La synthèse Fischer-Tropsch est une part essentielle du procédé XTL (X-To-Liquids, avec X = Gaz, Biomasse ou Charbon) qui convertit du gaz de synthèse en hydrocarbures pour carburants propres. Les catalyseurs à base de cobalt supportés sur des oxydes inorganiques constituent le meilleur compromis pour la production de paraffines à longues chaînes carbonées et de cires. L'efficacité du procédé FischerTropsch dépend très fortement de la performance du catalyseur à base de cobalt. La promotion de ce catalyseur par des métaux précieux peut très fortement améliorer ses performances. Cet article fait la revue des différents effets des métaux nobles sur la structure et la performance de catalyseurs à base de cobalt. Les impacts sur le coût et l'activité des catalyseurs apparaissent comme des éléments incontournables dans le design de catalyseurs performants pour la synthèse Fischer-Tropsch. (X-To-Liquids, with X = Gas, Biomass or Coal) Abstract -Promotion of Cobalt Fischer-Tropsch Catalysts with Noble Metals: a Review -FischerTropsch synthesis is a major part of XTL

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“…4(b) we observe a shift to lower binding energies, a merging of the Al sÀ1 and Al s peaks and an approaching of the Al i peak to the Al-surface ones, in fair agreement with experiment. The thickening of the AlO x layer in the presence of Ni NP obviously requires the dissociation of O 2 on the NP followed by spillover to the oxide surface and penetration through the alumina to the Ni 3 Al interface, where an additional Al-O layer is generated [26].…”

mentioning

confidence: 99%

Ordered Arrays of Size-Selected Oxide Nanoparticles

Gragnaniello

Barcaro

et al. 2012

Phys. Rev. Lett.

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A bottom-up approach to produce a long-range ordered superlattice of monodisperse and isomorphic metal-oxide nanoparticles (NP) supported onto an oxide substrate is demonstrated. The synthetic strategy consists of self-assembling metallic NP on an ultrathin nanopatterned aluminum oxide template followed by a morphology-conserving oxidation process, and is exemplified in the case of Ni, but is generally applicable to a wide range of metallic systems. Both fully oxidized and core-shell metal-metal-oxide particles are synthesized, up to 3-4 nm in diameter, and characterized via spectroscopic and theoretical tools. This opens up a new avenue for probing unit and ensemble effects on the properties of oxide materials in the nanoscale regime. DOI: 10.1103/PhysRevLett.108.195507 PACS numbers: 81.16.Pr, 61.46.Df, 75.75.Cd, 81.16.Rf Metal-oxide nanoparticles (NP) find widespread interest in fundamental science and bear promise for high-level applications in many emerging fields of the advanced nanotechnologies, from nanospintronics and high-density magnetic storage devices [1][2][3] to chemical sensing [4,5] and nanocatalysis [6,7]. The size, shape, and mutual interactions among the particles play a key role in determining the novel properties of these nanosized oxide materials [8,9]. For example, oxide NP may display anomalous magnetic behavior such as ferromagnetism vs antiferromagnetism in the bulk [2,3] or size-dependent magnetic structures and unusual spin couplings [8,10]. Model systems of NP with atomic-level control of size, shape, chemical composition, and interparticle distance are therefore crucial to clarify the emergent phenomena in oxide materials at the nanometer scale, and to disentangle the effects of the various intra-, inter-and support-particle interactions. However, such systems are difficult to prepare especially for particles below 50-100 nm, which are not accessible to lithographic techniques [5], while the traditional wet chemical methods only allow moderate design variations [11]. Here we describe the fabrication of one such system: an ordered superlattice of monodisperse and isomorphic nickel oxide NP, and its characterization via spectroscopic and theoretical tools. Both fully oxidized and core-shell metal-metal-oxide particles (the latter of interest, e.g., for exchange bias effects [1]) are synthesized via a bottom-up template-directed self-assembly strategy, opening up a new avenue for probing unit and ensemble effects on the physical and chemical properties of oxide materials, from molecule-type cluster sizes to the solid state limit. Our strategy consists of self-assembling metallic NP on an ultrathin nanopatterned aluminum oxide template followed by a morphology-conserving oxidation process, thus producing a superlattice of oxide NP decoupled from a conducting metal substrate by an ultrathin oxide layer, with a very narrow size distribution and identical shapes. We illustrate the procedure for the case of NiO NP, but the method is general (it has been tested for CoO particles with e...

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Oxidation of Alumina-Supported Co and Co−Pd Model Catalysts for the Fischer−Tropsch Reaction

Cited by 36 publications

References 59 publications

UHV Studies of Methanol Decomposition on Mono‐ and Bimetallic CoPd Nanoparticles Supported on Thin Alumina Films

UHV Studies of Methanol Decomposition on Mono‐ and Bimetallic CoPd Nanoparticles Supported on Thin Alumina Films

Promotion of Cobalt Fischer-Tropsch Catalysts with Noble Metals: a Review

Ordered Arrays of Size-Selected Oxide Nanoparticles

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