Determination of cobalt species in niobia supported catalysts

Noronha, Fábio B.; Perez, Carlos A.; Schmal, Martín; Fréty, R.

doi:10.1039/a809963d

Cited by 38 publications

(38 citation statements)

References 36 publications

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“…Overlap of diffraction lines with Nb 2 O 5 lines impedes detection of weak cobalt and cobalt oxide diffraction lines. The absence of crystalline cobalt oxide diffraction lines in Nb 2 O 5 -supported catalysts is in line with XRD observations by Noronha et al [29].…”

Section: Resultssupporting

confidence: 87%

“…For Nb 2 O 5 -supported cobalt catalysts, high selectivities toward heavy hydrocarbons were reported at 1 bar by Schmal and coworkers [20][21][22][23][24] and more recently at 20 bar by den Otter et al [6]. The promoting effect of niobia as support material at low pressure was extensively studied by XPS, TPR, TPO, CO TPD and IR spectroscopy and was attributed to partial reduction of the support and consequent strong metal support interaction (SMSI) [25][26][27][28][29]. The presence of Co 0 -NbO x species was confirmed by Mendes et al in Co/ Nb 2 O 5 catalysts [27] and model catalysts [28].…”

Section: Introductionmentioning

confidence: 95%

See 1 more Smart Citation

On the superior activity and selectivity of PtCo/Nb2O5 Fischer Tropsch catalysts

Otter

Yoshida

Ledesma

et al. 2016

Journal of Catalysis

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Section: Resultssupporting

confidence: 87%

Section: Introductionmentioning

confidence: 95%

On the superior activity and selectivity of PtCo/Nb2O5 Fischer Tropsch catalysts

Otter

Yoshida

Ledesma

et al. 2016

Journal of Catalysis

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“…6a) consist of two main lines (i.e., 2p 3/2 at~781 eV and 2p 1/2 at~797 eV) with the spin-orbit splitting of~16 eV, as reported in the literature. [32][33][34][35] Most of the cobalt oxides and hydroxides are not distinguishable based only on the binding energy for the Co 2p main peaks. On the other hand, the secondary features in the spectra (shake-up satellites and spin-orbit splitting) are useful in identifying the different Co types.…”

Section: Resultsmentioning

confidence: 99%

Catalytic activity of Co-åkermanite and Co-pyroxene in oxidation reactions

Mihailova

MehandjievDimitar

2011

Can. J. Chem.

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Two calcium-cobalt silicates were synthesized in which cobalt occupies different structural positions. The crystal phases belong to two main structural silicate types. In the Co-åkermanite structure (Ca 2 CoSi 2 O 7 ), cobalt cations take tetrahedral coordination toward oxygen atoms. In the Co-pyroxene structure of CaCoSi2O6, cobalt displays octahedral coordination. Ca2CoSi2O7 was prepared by solid-phase synthesis and CaCoSi2O6 was prepared by sol-gel method. The synthesis of the phases was confirmed by XRD, FTIR, and EPR data. On the basis of the XPS analysis, it can be concluded that Co 2+ cations exist in the studied silicates. Thus, it is possible to study the catalytic activity of two silicate phases containing Co 2+ cations in different coordinations: tetrahedral and octahedral. It was found that cobalt silicates with crystal structures corresponding to pyroxene and åkermanite possess catalytic activity in the reactions of complete oxidation of CO and toluene. Co-pyroxene exhibits higher catalytic activity than Co-åkermanite, but the higher cobalt content on the surface of Co-pyroxene should also be taken into account. Then, it turns out that catalytically active complexes with Со 2+ ions in tetrahedral coordination are more efficient than those with such ions in octahedral coordination when equal concentrations of cobalt were used on the surface of the catalysts.Résumé : On a réalisé la synthèse de deux silicates de calcium et de cobalt dans lesquels l'atome de cobalt occupe des positions diverses dans la structure. Les phases cristallines appartiennent à deux types principaux de structures de silicate. Dans la structure åkermanite du Ca2CoSi2O7, les cations du cobalt occupent des positions de coordination tétraédrique par rapport aux atomes d'oxygène. Le Ca2CoSi2O7 a été préparé par une synthèse en phase solide alors que le CaCoSi2O6 a été obtenu par méthode sol-gel. Les synthèses des phases ont été confirmées par des données de diffraction des rayons-X (DRX), d'infrarouge à transformée de Fourier (IR-TF) et résonance paramagnétique électronique (RPE). Sur la base d'analyse de données de spectroscopie photoélectronique des rayons-X (SPX), il est possible de conclure que, dans les silicates étudiés, il existe des cations Co 2+ . Il est donc possible d'étudier l'activité catalytique des deux phases de silicate contenant des cations Co 2+ dans des environnements de coordination différents : tétraédrique et octaédrique. On a trouvé que les silicates de cobalt avec une structure cristalline correspondant à celle du pyroxène et de l'åkermanite présentent une activité catalytique dans les réactions d'oxydation complète du CO et du toluène. Le Co-pyroxène possède une activité catalytique plus élevée que celle de la Co-åkermanite; toutefois, on doit tenir compte du fait que la teneur en cobalt est plus élevée sur la surface du Co-pyroxène. Il en découle alors que, pour des concentrations identiques de cobalt à la surface des catalyseurs, les complexes catalytiquement actifs comportant des ions Co 2+ en coordinatio...

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“…No clear shake up peaks were observed, indicating that cobalt is mostly present as Co 3+ , which would be consistent with the presence of Co 3 O 4 in which 2/3 of Co is in 3+ oxidation state. XPS spectra of bulk Co 3 O 4 with no clear shake-up peaks have been reported previously [33][34][35].…”

Section: X-ray Photoelectron Spectroscopymentioning

confidence: 94%

Low-temperature Oxidation of Carbon Monoxide on Co/ZrO2

2007

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A 10%Co/ZrO 2 catalyst prepared by impregnation was tested for its activity for the oxidation of CO to CO 2 in excess oxygen. Activity tests showed that conversion could be obtained at temperatures as low as 20°C. Timeon-stream studies showed no loss of activity in these experiments, indicating that this catalyst is stable in the experimental oxidizing conditions. The activation energy for the CO to CO 2 oxidation reaction was calculated as E a = 54 kJ/mol over this catalyst. Characterization of the material by thermogravimetric analysis, temperature-programmed techniques, X-ray photoelectron spectroscopy, and laser Raman spectroscopy indicate that Co 3 O 4 is present on monoclinic ZrO 2 after the calcination of the catalyst.

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Determination of cobalt species in niobia supported catalysts

Cited by 38 publications

References 36 publications

On the superior activity and selectivity of PtCo/Nb2O5 Fischer Tropsch catalysts

On the superior activity and selectivity of PtCo/Nb2O5 Fischer Tropsch catalysts

Catalytic activity of Co-åkermanite and Co-pyroxene in oxidation reactions

Low-temperature Oxidation of Carbon Monoxide on Co/ZrO2

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