ChemInform Abstract: Surface Synergisms Between Copper and Its Oxides. Part 1. Isopropanol Dehydrogenation Over Unsupported CuO, Cu2O, and Cu Metal

Cunningham, Joseph; Al-Sayyed, Ghassan; Cronin, John A.; Fierro, J.L.G.; Healy, C.; Hirschwald, W.; Ilyas, Mohammad; Tobin, J.

doi:10.1002/chin.198707119

Cited by 3 publications

(4 citation statements)

References 1 publication

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“…Another striking feature of the behavior of the alloys studied is the marked difference found between the chemical states of copper of Cu−Ti and the other two alloys. According to literature data, either metallic copper (Cu 0 ) , is involved in the dehydrogenation of alcohols to carbonyl compounds or the coexistence of metallic and oxidized copper species , is required. On the basis of these observations as well as the inactivity of Cu−Ti alloy in such dehydrogenations, the lack of surface Cu 0 could be predicted …”

Section: Discussionmentioning

confidence: 99%

Surface Characterization of Cu−M (M = Ti, Zr, or Hf) Alloy Powder Catalysts

Molnár¹,

and²,

Szépvölgyi³

et al. 1998

J. Phys. Chem. B

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X-ray photoelectron spectroscopy was used for surface characterization of amorphous Cu−M alloy powders (Cu40Ti60, Cu50Zr50, and Cu65Hf35) produced by mechanical alloying of the constituents. When used as catalyst in the dehydrogenation of alcohols Cu−Zr and Cu−Hf were found to undergo structural changes resulting in surface copper enrichment with a substantial fraction of copper being in fully reduced, metallic (Cu0) state. This result accounts for the high and stable catalytic activity of Cu−Zr and Cu−Hf in the transformations of alcohols. In contrast, when Cu−Ti is used in inert atmosphere, surface enrichment of titanium is observed. Although segregation of copper occurs in the presence of hydrogen, only oxidized copper species are detected on the surface. In either case, the catalytic activity of Cu−Ti is inferior to the other two alloy samples. TiH2 is shown by XRD to be the characteristic species formed under hydrogen. This is stable in the presence of hydrogen and, therefore, Cu acts as an oxygen scavenger and forms oxidized surface species that do not show catalytic activity.

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Section: Discussionmentioning

confidence: 99%

Surface Characterization of Cu−M (M = Ti, Zr, or Hf) Alloy Powder Catalysts

Molnár¹,

and²,

Szépvölgyi³

et al. 1998

J. Phys. Chem. B

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“…Shen et al adopted three commonly applied preparation methods to prepare nanosized CuO/CeO 2 catalysts, and they found that there was a correlation between preparation approach and catalytic property: the stronger the interaction between copper and ceria is, the easier the CO oxidation reaction will be. It has been widely reported that there exists a strong metal–support interaction (SMSI) between the catalyst particles and support material especially in nanosized composite catalysts, and this SMSI effect between copper and cerium oxide during the CO oxidation reaction is also regarded as a key factor in determining the redox features and, consequently, the catalytic behavior. − In this SMSI effect, the interaction between the Ce 4+ /Ce 3+ and the Cu 2+ /Cu (2−δ)+ couples has been proposed to take place at boundaries of nanocrystalline ceria (CeO 2– x ), which leads to the valence changes of copper species, and even metal Cu species can be present as a transient state during the reaction. Skarman et al attributed the high activity of CuO/CeO 2 to the quick and reversible redox process of superficial Cu(I)/(II) couples in a strong synergetic interaction with the nanocrystalline ceria, which comprehensively elaborated the SMSI effect in CuO/CeO 2 .…”

Section: Synergetic Catalytic Effectsmentioning

confidence: 99%

On the Synergetic Catalytic Effect in Heterogeneous Nanocomposite Catalysts

2012

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“…It is well-known that the oxidation state of supported transition metal species has an important effect on the activity in various catalytic reactions. For instance, the reduced Cu 0 and Cu 1+ species are catalytically more active than Cu 2+ in NO reduction by NH 3 , methanol synthesis, and the dehydrogenation of 2-propanol to 2-propanone . For the latter reaction, there is also some evidence indicating that the coexistence of Cu 0 and Cu 1+ represents the most active state .…”

Section: Introductionmentioning

confidence: 99%

“…For instance, the reduced Cu 0 and Cu 1+ species are catalytically more active than Cu 2+ in NO reduction by NH 3 , methanol synthesis, and the dehydrogenation of 2-propanol to 2-propanone . For the latter reaction, there is also some evidence indicating that the coexistence of Cu 0 and Cu 1+ represents the most active state . Typical dehydrogenation catalysts, such as Cu/Cr 2 O 3 , have to be activated by hydrogen reduction.…”

Section: Introductionmentioning

confidence: 99%

Redox Properties of Nanocrystalline Cu-Doped Cerium Oxide Studied by Isothermal Gravimetric Analysis and X-ray Photoelectron Spectroscopy

1999

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Nanostructured CeO2 - x and Cu0.15Ce0.85O2 - x were synthesized by high-pressure magnetron sputtering. X-ray diffraction was used for phase analysis and grain size characterization. The structural analysis indicated that Cu was highly dispersed, which could be explained by surface segregation on cerium oxide nanocrystals. The reduction and oxidation of dispersed copper in nanostructured Cu0.15Ce0.85O2 - x was investigated by isothermal gravimetric analysis (IGA) and X-ray photoelectron spectroscopy (XPS). In IGA, the sample weight was measured at constant temperature during in situ reduction and oxidation in 2% CO/He or 5% H2/He and 15% O2/He, respectively. The weight changes of microcrystalline CeO2 and nanocrystalline CeO2 - x and Cu0.15Ce0.85O2 - x samples were measured at temperatures between 200 and 500 °C. The analysis revealed that more than one oxygen atom was extracted per Cu atom in Cu0.15Ce0.85O2 - x during reduction, which was reversibly restored during oxidation. The Cu valence state in Cu0.15Ce0.85O2 - x after oxidation or reduction was independently determined by XPS. The Cu 2p core-level spectra and LMM Auger spectra of Cu0.15Ce0.85O2 - x were compared with those of a polycrystalline copper reference. The analysis showed that all three oxidation states of copper (i.e., 0, 1+, and 2+) could be present depending on the reduction/oxidation specifications. Furthermore, Cu0 and Cu1+ were found to coexist in a stable state under certain conditions.

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ChemInform Abstract: Surface Synergisms Between Copper and Its Oxides. Part 1. Isopropanol Dehydrogenation Over Unsupported CuO, Cu2O, and Cu Metal

Cited by 3 publications

References 1 publication

Surface Characterization of Cu−M (M = Ti, Zr, or Hf) Alloy Powder Catalysts

Surface Characterization of Cu−M (M = Ti, Zr, or Hf) Alloy Powder Catalysts

On the Synergetic Catalytic Effect in Heterogeneous Nanocomposite Catalysts

Redox Properties of Nanocrystalline Cu-Doped Cerium Oxide Studied by Isothermal Gravimetric Analysis and X-ray Photoelectron Spectroscopy

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