- Title
- The complete oxidation of isobutane over CeO2 and Au/CeO2, and the composite catalysts MOx/CeO2 and Au/MOx/CeO2 (Mn+ = Mn, Fe, Co and Ni): the effects of gold nanoparticles obtained from n-hexanethiolate-stabilized gold nanoparticles
- Creator
- Almukhlifi, Hanadi A.; Burns, Robert C.
- Relation
- Journal of Molecular Catalysis A: Chemical Vol. 415, Issue May 2016, p. 131-143
- Publisher Link
- http://dx.doi.org/10.1016/j.molcata.2016.01.030
- Publisher
- Elsevier
- Resource Type
- journal article
- Date
- 2016
- Description
- The complete oxidation of isobutane has been studied over CeO₂ and Au/CeO₂, as well as the composite catalysts MOx/CeO₂ and Au/MOx/CeO₂, where M = Mn, Fe, Co and Ni, using a range of CeO₂ surface areas. The catalytic ability of CeO₂ depended on the specific surface area, and the addition of gold always increased activity. Similarly, addition of MOx to CeO₂ (M:Ce = 1:10) increased catalytic activity, and there was a synergic interaction between the MOx and CeO₂ phases. For Au/MOx/CeO₂ catalysts the presence of gold nanoparticles did not affect the initial reaction temperature or that for 100% conversion, or the apparent activation energy compared to MOx/CeO₂ catalysts. The rate determining step in these reactions is suggested to be C—H bond activation. This was supported by TG/DTA studies under 10% H₂ in N₂ that showed there was no correlation between the catalysis results and the temperature of initial mass loss of lattice oxygen. Gold nanoparticles (5 wt%) were introduced by adsorption and subsequent thermolysis of preformed n-hexanethiolate-stabilized gold nanoparticles. STEM and XRD studies showed that the average size of the gold nanoparticles depended on the surface area. Introduction of gold nanoparticles by this method introduces a small amount of sulfur as adsorbed sulfate, but this did not have any major poisoning effect on isobutane oxidation. Gold 4f7/2 XPS studies on Au/MOx/CeO₂ showed that the only common gold species was Au(0), suggesting that higher oxidation states were not important in the oxidation, while Ce 3d5/2 studies established the presence of Ce(III) in addition to Ce(IV), indicating their involvement in the Mars-van Krevelen mechanism, including possible participation in reoxidation of reduced MOx.
- Subject
- isobutane oxidation; transition metal oxides; cerium dioxide; gold nanoparticles; n-hexanethiolate-stabilized gold nanoparticles
- Identifier
- http://hdl.handle.net/1959.13/1344386
- Identifier
- uon:29404
- Identifier
- ISSN:1381-1169
- Language
- eng
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