Vanadium pentoxide powder

The vanadium pentoxide catalyst Is prepared as follows Suspend 5 g. of pure ammonium vanadate in 50 ml. of water and add slowly 7 5 ml. of pure concentrated hydrochloric acid. Allow the reddish-brown, semi-colloidal precipitate to settle (preferably overnight), decant the supernatant solution, and wash the precipitate several times by decantation. Finally, suspend the precipitate in 76 ml. of water and allow it to stand for 3 days. This treatment renders the precipitate granular and easy to 6lter. Filter the precipitate with suction, wash it several times with cold 5 p>er cent, sodium chloride solution to remove hydrochloric acid. Dry the product at 120° for 12 hours, grind it in a mortar to a fine powder, and heat again at 120° for 12 hours. The yield of catalyst is about 3 - 5 g. 

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. 

The preparation of ferrovanadium by this route is carried out batchwise in refractory-lined open reactors, with vanadium pentoxide, aluminum powder, iron scrap and lime or fluorspar constituting the charge. The reactions once initiated, proceed briskly to completion. The reaction heat is sufficient to melt the ferrovanadium and the alumina-lime/fluor-spar slag, which readily separate due to density difference. The aluminothermic ferroalloy product contains practically no carbon. 

Violence of reaction depends on concentration of acid and scale and proportion of reactants. The following observations were made with additions to 2-3 drops of ca. 90% acid. Nickel powder, becomes violent mercury, colloidal silver and thallium powder readily cause explosions zinc powder causes a violent explosion immediately. Iron powder is ineffective alone, but a trace of manganese dioxide promotes deflagration. Barium peroxide, copper(I) oxide, impure chromium trioxide, iridium dioxide, lead dioxide, manganese dioxide and vanadium pentoxide all cause violent decomposition, sometimes accelerating to explosion. Lead(II) oxide, lead(II),(IV) oxide and sodium peroxide all cause an immediate violent explosion. 

Vanadium pentoxide (V Oj) is a reddish-yellow powder extracted from minerals using strong acids or alkalies. In addition to being used as a catalyst for many organic chemical reactions, it is used in photography and in UV-protected windowpanes and to color ceramics and dye cloth. 

Asbestos, which increases the burning surface of powder mixtures, is also added and a small amount of vanadium pentoxide which exerts an advantageous influence on the uniformity of burning of a mixture. 

Halogenation in the presence of sulphur, or by means of sulphur halides, is also available. When chlorine is conducted into a mixture of vanadium pentoxide and sulphur, or when powdered vanadium pentoxide is treated with sulphur monochloride vapours, an immediate reaction sets in, with formation of vanadium oxytrichloride.2 A quantitative yield of this compound is also obtained when vanadium trichloride is heated in oxygen at 500° to 600° C.3... 

Vanadyl Dibromide, VOBr2, is obtained by passing bromine vapour or, preferably, a mixture of sulphur bromide, SaBra, and bromine over a mixture of vanadium pentoxide and sulphur at a red heat the product is heated in vacuo at 240° C., whereupon the vanadyl dibromide is obtained as a yellow powder.8 An alternative method of preparation consists in heating vanadium oxytribromide, VOBr3, to 180° C.9 Vanadyl dibromide is no doubt present in the blue solution which results when hypovanadic oxide, VOa, is dissolved in hydrobromic acid. 

V0.V205 is produced as a dark blue, crystalline powder when either vanadium pentoxide or ammonium metavanadate is heated with excess of powdered arsenic, or when ammonium metavanadate is reduced with sulphur dioxide at a red heat. It dissolves in nitric acid to a blue solution.8... 

V02.V205 is obtained as a dark blue or black powder with a metallic lustre by dissolving vanadium pentoxide in caustic potash.9... 

Vanadium pentoxide dissolves in acids, both organic and inorganic, to form vanadyl or unstable vanadic salts,7 and in alkalis to produce ortho-, pyro-, meta-, and poly-vanadates. The physico-chemical changes involved when vanadium pentoxide is heated with various basic oxides in the powder state have been investigated by Tammann.8 On being digested with liquid ammonia slow absorption of ammonia takes place the composition of the product has not been definitely established.9 The oxide also dissolves in alcohols to produce esters,10 and combines with methylamine and ethylamine to form compounds of the type 2(R.NHB).V205, where R represents the alkyl radical.11... 

Barium Pyrovanadate, BaaVaO is precipitated on addition of barium chloride to a solution of sodium pyrovanadate or of other vanadates in the presence of ammonia.3 It has more recently been prepared by the action of barium peroxide on vanadium pentoxide.4 It is a white, amorphous powder which melts above 868° C.5... 

Thallium Pyrovanadate, T14V20 is precipitated as a light yellow powder by the addition of thallium sulphate to a cold, saturated solution of sodium orthovanadate. It also results on fusing a mixture of vanadium pentoxide and thallium carbonate.14 It melts at 454°15 or 416° C.,16 and is soluble in about 5000 parts of water at 14° C. 

W. Muthmann and co-workers also reported that finely divided vanadium reacts with nitrogen at a red-heat. The reaction is so slow that 20-24 hrs. are needed for the increase in weight to become constant nitrogen is also absorbed at dull redness, but the action is still slower. In contradistinction to H. E. Roscoe, the composition of the product approximated vanadium heminitride, V2N. R. E. Slade and G. I. Higson found that vanadium nitride dissociates at 1203° and 02 mm. press. According to N. Whitehouse, at a white-heat vanadium forms the mononitride. The velvety-black powder is unchanged in air when heated in air, however, it forms vanadium pentoxide water, and dil. hydrochloric acid, hot or cold, have no action, but it dissolves in cold dil. nitric acid. G. Gore found that vanadium nitride is insoluble in liquid ammonia. It is not affected by alkali-lye, but with fused potassium hydroxide, ammonia is evolved. 

Concentrated nitric acid (140 c.c.) containing vanadium pentoxide (0-l grm.) is warmed gently in a litre-flask it is then placed in a fume-cupboard and powdered cane-sugar (20 gms.) is added. 

Anthracene was oxidized to anthraquinone by warming a mixture of 90 g. of finely powdered hydrocarbon, 0.5 g. of vanadium pentoxide, 76 g. of sodium chlorate, 1 1. of acetic acid, and 200 ml. of 2% sulfuric acid under reflux until a vigorous reaction set in. After eventual brief refluxing, anthraquinone was obtained in 88-91% yield. The method is not suitable for the oxidation of hydrocarbons of the naphthalene or phenanthrene series to the quinones or for oxidation of acenaphthene or fluorene. 

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