Binary vanadium oxides

Simple Binary and Related Compounds.—Oxides. The information presently available concerning the crystal structures and properties of vanadium oxides has been tabulated. 

The development of implanted medical defibrillators required a high-rate, long-life battery system. In defibrillators, the CFx is used in combination with silver vanadium oxide (SVO) cathode materials [17]. A binary mixture of CFx and SVO are combined to form the cathode, giving the best features of SVO and CFx. Compared to CFx, the SVO has superior pulse current capability, but lower energy storage capability. The cell reactions are given in Equations 10.7 and 10.8. 

Wang et al. (18) have studied binary and ternary mixtures of titanium oxide with zirconium oxide, vanadium oxide and iron oxide, among others. They reported that the by-products are produced in small amounts. Some mixtures are as active or more active than the iron oxide catalyst but are less selective. These researchers noted that in addition to the aforementioned reactions, reactions 3 to 5, the following reactions are significant ... 

Binary vanadium-titanium oxide catalysts with various ratios of vanadium oxide and titania, as well as individual oxides of vanadium and titanium were examined in oxidation of P-picoline. Nicotinic acid, 3-pyridinecarbaldehyde, and CO2 were the reaction products over all the catalysts. The binary catalysts and individual vanadium oxide were highly selective for nicotinic acid, the most effective in P-picoline oxidation were the samples containing 20% and more of vanadium pentoxide. A regular stacking of crystallites of V2O5 and Ti02 was found to be the characteristic feature of the structure of the most effective compositions. 

IR spectrum of individual titania and the IR spectra of the binary catalysts coincide well with the spectrum of anatase [8] at 200-1300 cm". However in the spectra recorded for individual Ti02 and the sample containing 5% of vanadium oxide, the maxima of broad absorption bands (a.b.) at 540 and 342 cm", which are characteristic of anatase, are shifted downfield to 517 and 332 cm , at the same time a.b. at 965 and 1050 cm with 1070 and 1125 cm shoulders, respectively, are observed, that indicates the presence of sulfate-ion... 

Fig.4 shows the selectivities for the reaction products and the rate of oxidation of P-picoline against composition of the vanadium-titania system. All the binary vanadium-titania catalysts and the individual vanadium oxide reveal high selectivities for nicotinic acid. The selectivity for nicotinic acid increases from 75 to 90% and the rate of p-picoline oxidation increases by three times as the concentration of V2O5 increases from 5 to 20%, no further... 

All the binary vanadium-titania catalysts and vanadium oxide are selective for oxidation of P-picoline to nicotinic acid. The only by-product is carbon dioxide. The selectivity for CO2 is no more than 10% even at high conversions observed for all of the binary catalysts and individual vanadium pentoxide. However we can distinguish the most effective compositions... 

Thermal spreading of vanadium oxide over titania-silica binary oxide support... 

Reddy, B.M., Ganesh, I, and Chowdhnry, B. Design of stable and reactive vanadium oxide catalysts supported on binary oxides. Catal Today 1999, 49, 115-121. 

The binary phase diagrams of the titanium oxides and sulphides are very complex with the formation of a very high number of intermediate phases (a similar behaviour is observed also for other intermediate transition metals such as vanadium). In the... 

In contrast to the aforementioned binary oxides, V2Os has a stronger oxidation power and is able to attack hydrogen attached to the aromatic nucleus. Sometimes attention is drawn to the importance of a layer structure in the catalyst or to geometric factors (e.g. Sachtler [270]). Unexpectedly, however, very effective vanadium-based catalysts exist which operate in the molten state, indicating that a fixed structure is not important. The catalytic activity of molten oxide phases seems to occur exclusively in the oxidation of aromatic hydrocarbons over V2Os-based catalysts, such systems have not been reported for the selective oxidation of olefins. 

Other common anode materials for thermal batteries are lithium alloys, such as Li/Al and Li/B, lithium metal in a porous nickel or iron matrix, magnesium and calcium. Alternative cathode constituents include CaCr04 and the oxides of copper, iron or vanadium. Other electrolytes used are binary KBr-LiBr mixtures, ternary LiF-LiCl-LiBr mixtures and, more generally, all lithium halide systems, which are used particularly to prevent electrolyte composition changes and freezing out at high rates when lithium-based anodes are employed. 

In the present chapter, which deals with theoretical concepts applied to vanadium and molybdenum oxide surfaces, we will restrict the discussion to binary oxide systems. So far, mixed metal oxide systems have not been studied by quantitative theory. Theoretical methods that have been used to study oxide surfaces can be classified according to the approximations made in the system geometry where two different concepts are applied at present, local cluster and repeated slab models. Local cluster models are based on the assumption that the physical/chemical behavior at selected surface sites can be described by finite sections cut out from the oxide surface. These sections (surface clusters) are treated as fictitious molecules with or without additional boundary conditions to take the effect of environmental coupling into account. Therefore, their electro-... 

The most studied systems for oxidative propane upgrading are vanadium [2], vanadium-antimony [3], vanadium-molybdenum [4], and vanadium-phosphorus [5] based catalysts. Another family of light paraffin oxidation catalysts are molybdenum based systems, e.g. nickel-molybdates [6], cobalt-molybdates [7] and various metal-molybdates [8-9]. Recently, we investigated binary molybdates of the formula AM0O4 where A = Ni, Co, Mg, Mn, and/or Zn and some ternary Ni-Co-molybdates promoted with P, Bi, Fe, Cr, V, Ce, K or Cs [10-11]. A good representative of these systems is the composition Nio.5Coo.5Mo04 which was recently selected for an in depth kinetic study [12] and whose mechanistic aspects are now further illuminated here. 

We can conclude that the formation of the interface between the crystallites of anatase and vanadium pentoxide, which is likely to produce the states of vanadium and oxygen other than those in the individual oxides, can be responsible for a higher efficiency of the binary catalysts. 

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