https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:2515 Sat 24 Mar 2018 08:31:00 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:1406 Ni(II)>Zn(II)>Mn(III)>Cu(II), with Mn(II) undergoing oxidation by H₂O₂ under the reaction conditions. The order likely corresponds to a combination of the catalytic abilities of the transition metal-substituted lacunary anions in conjunction with their rates of decomposition by H₂O₂, and/or the catalytic abilities of the freed transition metals and peroxo-products themselves]]> Sat 24 Mar 2018 08:28:16 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:29404 x/CeO₂ and Au/MO_x/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 MO_x to CeO₂ (M:Ce = 1:10) increased catalytic activity, and there was a synergic interaction between the MO_x and CeO₂ phases. For Au/MO_x/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 MO_x/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 4f_7/2 XPS studies on Au/MO_x/CeO₂ showed that the only common gold species was Au(0), suggesting that higher oxidation states were not important in the oxidation, while Ce 3d_5/2 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 MO_x.]]> Sat 24 Mar 2018 07:36:18 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:26511 3/2 XPS studies indicated that all catalysts exhibited surface V(V) and V(IV), while V(III) was present in those catalysts that generated V(III)-containing products. This suggests that catalytic activity depends on the rate of reoxidation of the lower oxidation states to V(V). Gold 4f_7/2 XPS studies always indicated the presence of Au(0) and Au(I), and for some catalysts Au(III). The highest yields of isobutene correlate with the lowest Au(I) content. The reduction products Co₂V^IVO₄ and ZnV^III₂O₄ were compared in their activities with Co₂V₂O₇ and α-Zn₂V₂O₇. The reduced phase Co₂VO₄ proved to be a good catalyst, comparable to the best 5 wt% Au/M₂V₂O₇ compositions.]]> Sat 24 Mar 2018 07:35:32 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:29715 β-MnO₂ > α-Fe₂O₃, with the position of NiO dependent on the Ni³⁺ content which changes with temperature. Preformed n-hexanethiolate-stabilized gold nanoparticles, following adsorption and thermolysis in air, introduce a small amount of sulfur as adsorbed sulfate. The sulfate appears to block the reoxidation step in the Mars-van Krevelen mechanism. This can have a significant effect on catalytic activity, as observed for β-MnO₂. TEM/STEM studies indicate that gold nanoparticles of 2–4 nm in diameter form, which depends on the identity of the metal oxide and its specific surface area. Gold nanoparticle size effects have been studied on NiO, and show that the apparent activation energy and temperature of initial reaction depend on nanoparticle size. Comparisons of the multicomponent Au/MO_x/γ-Al₂O₃ (M:Al = 1:10) catalysts, where M = Mn, Fe, Co, Ni, have also been studied, and all are more active catalysts than Au/γ-Al₂O₃, but less active than the unsupported catalysts. Gold 4f_7/2 XPS studies on Au/MO_x and Au/MO_x/γ-Al₂O₃ have shown that the only common species present is Au(0), suggesting that higher oxidation states of Au are not important in oxidation catalysis.]]> Sat 24 Mar 2018 07:33:24 AEDT ]]>