Vanadium oxide cation

Bell R C, Zemski K A, Kerns K P, Deng H T and Castleman A W Jr 1998 Reactivities and collision-induced dissociation of vanadium oxide duster cations J. Phys. Chem. A 102 1733... 

For solvent extraction of a tetravalent vanadium oxyvanadium cation, the leach solution is acidified to ca pH 1.6—2.0 by addition of sulfuric acid, and the redox potential is adjusted to —250 mV by heating and reaction with iron powder. Vanadium is extracted from the blue solution in ca six countercurrent mixer—settler stages by a kerosene solution of 5—6 wt % di-2-ethyIhexyl phosphoric acid (EHPA) and 3 wt % tributyl phosphate (TBP). The organic solvent is stripped by a 15 wt % sulfuric acid solution. The rich strip Hquor containing ca 50—65 g V20 /L is oxidized batchwise initially at pH 0.3 by addition of sodium chlorate then it is heated to 70°C and agitated during the addition of NH to raise the pH to 0.6. Vanadium pentoxide of 98—99% grade precipitates, is removed by filtration, and then is fused and flaked. 

For vanadium solvent extraction, Hon powder can be added to reduce pentavalent vanadium to quadrivalent and trivalent Hon to divalent at a redox potential of —150 mV. The pH is adjusted to 2 by addition of NH, and an oxyvanadium cation is extracted in four countercurrent stages of mixer—settlers by a diesel oil solution of EHPA. Vanadium is stripped from the organic solvent with a 15 wt % sulfuric acid solution in four countercurrent stages. Addition of NH, steam, and sodium chlorate to the strip Hquor results in the precipitation of vanadium oxides, which are filtered, dried, fused, and flaked (22). Vanadium can also be extracted from oxidized uranium raffinate by solvent extraction with a tertiary amine, and ammonium metavanadate is produced from the soda-ash strip Hquor. Fused and flaked pentoxide is made from the ammonium metavanadate (23). 

XRD patterns of the prepared samples V-Mo-Zeolite are similar to that of zeolites which suggests that the metal species (i.e. oxide, cations,...) are well dispersed through the zeolites structure and the absence of bulk phases in the XRD patterns implies that for these samples the molybdenum and vanadium oxides are present in either a nanocrystalline state or as a small crystallites which measured less than 4 nm in diameter. Furthermore, XRD and FTIR (1500-400 cm 1) showed no significant damage of the zeolite host structure after exchange and thermal treatment except for the sample V2MoMor. 

The reactions of the vanadium oxide cluster cations with CCI4 were of three types (248). The small cluster ions reacted by transfer of a chloride ion. The larger clusters starting with the V4OJ+ series reacted by the addition of a chlorine atom to the cluster or the loss of one oxygen atom and the addition of two chlorine atoms. 

This paper summarized our current understanding of the factors that determine selectivity for dehydrogenation versus formation of oxygen-containing products in the oxidation of light alkanes. From the patterns of product distribution in the oxidation of C2 to C6 alkanes obtained with supported vanadium oxide, orthovanadates of cations of different reduction potentials, and vanadates of different bonding units of VO in the active sites, it was shown that the selectivities can be explained by the probability of the surface alkyl species (or the... 

Electrochemically characterized V(V) complexes which lack oxo ligands are somewhat rare. Many of those which are known are the result of preparative studies guided by CV results on V(IV) systems. For example, a series of imidovanadium(IV) complexes containing the tetradentate dianionic 5,7,12,14-tetramethyldibenzo[b, i] [1, 4, 8, 11] tetraazacyclotetradecinato moiety (TMTAA ) was reported [73], and diamagnetic vanadium(V) cations [(TMTAA)V = NR]+ (4) were prepared by oxidation of... 

The known vanadium carbonyl cations are of two types, namely a tetracarbonyl, [AreneV(CO)4]+, and a dicarbonyl, [Cp2V(CO)2]+. The tetracarbonyl derivatives are readily prepared under mild conditions by the reaction of an arene with vanadium hexacarbonyl. The arenes used include benzene, its methyl derivatives 28, 29), naphthalene, and anisole 29). The cation is probably formed by oxidation of the intermediary arene vanadium tricarbonyl. 

Mn-V-oxides have been prepared starting from vanadium oxide-dodecylamine composite nanotubes.87 The composite nanotubes were prepared by mixing V203 with dodecylamine in the presence of ethanol and water. The amine templates can be easily substituted or even ion-exchanged with ions like Mn2+ in an aqueous alcohol solution to obtain the Mn-V-0 nanotubes. Most of the nanotubes had open ends, while some of them had closed ends, with the side of the tubes wrapped around the end to close it. The Mn2 ions replace the organic cations in the structures and hence are intercalated in between the layers. 

On metals that produce substantial yields of oxygenates, such as rhodium, promotion by reducible oxides (e.g., molybdenum or vanadium oxides) appears beneficial 76—78). The key property of the cation of the promoting oxide is a weak affinity for CO combined with a strong affinity for oxygen. An aftractive hypothesis to explain the role of the promoting cations is that the reducible cation provides a site for the O atom generated upon CO dissociation, whereas CO interacts only weakly with the promoting cations. 

It is known that under ambient conditions supported vanadium oxide exists as a +5 cation (9). For this... 

Vanadium oxides of various stoichiometries exist, related to the different oxidation states of the cation. V2O5 has the vanadium atoms with the highest valency and a (f configuration. It is insulating at low temperature, with an orthorhombic layered structure made of VO5 pyramids sharing corners and edges. A transition towards a metallic phase takes... 

Bell RC, Zemski KA, Castleman AW Jr (1999) Gas-phase chemistry of vanadium oxide cluster cations 3. Reactions with CCl. J Phys Chem A 103 1585... 

Zemski KA, Justes DR, Bell RC, Castleman AW Jr (2001) Reactions of niobium and tantalum oxide cluster cations and anions with n-butane. J Phys Chem A 105 4410 Bell RC, Castleman AW Jr (2002) Reactions of vanadium oxide cluster ions with 1, 3-butadiene and isomers of butane. J Phys Chem A 106 9893... 

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