https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:22329 Wed 11 Apr 2018 09:26:58 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:12410 xH_3–3x[PMo₁₂O₄₀] (M = Al, La or Ce; 0 ≤ x ≤ 1). These compounds were analyzed by XRD and adsorption isotherm. Aluminum addition causes a primitive cubic phase, while lanthanum and cerium yield body-centered structures. La and Ce addition reduces surface area of phosphomolybdate structure. Temperature-programmed experiments for the selective oxidation of isobutane yielded methacrolein, 3-methyl-2-oxetanone (lactone), acetic acid (not with aluminous compounds), propene (only with aluminous compounds), carbon dioxide and water. The preference for propene rather than acetic acid formation with Al³⁺ may be due to the smaller cation size, or primitive cubic structure. These products form via two distinct reaction processes, labeled categories 1 and 2. Category 1 formation is associated with isobutane forming products on the surface, but reaction rate determined by bulk migration of charged particles. Category 2 formation is concerned with isobutane penetrating deep within the bulk of the substrate and forming products which subsequently desorb in a series of bell-shaped humps. Methacrolein forms via both category 1 and 2, whilst all other products form via category 2 exclusively. Kinetic analysis showed apparent activation barriers for category 1 methacrolein formation range from 67 ± 2 kJ mol^-1to[350 kJ mol^-1, and occur in groups with small, medium and large activation barriers. The addition of +3 metal cations to the phosphomolybdate anion increase thermal stability, significantly decreasing deactivation; IR spectroscopy shows that the Keggin structure remains intact during temperature-programmed experiments with the Al, La and Ce salts.]]> Sat 24 Mar 2018 08:14:51 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:5049 Sat 24 Mar 2018 07:48:44 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 ]]>