Metals vanadium

Much of the vanadium metal being produced is now made by calcium reduction of V2O5 in a pressure vessel, an adaption of a process developed by McKechnie and Seybair. 

Ductile vanadium is commercially available. Commercial vanadium metal, of about 95% purity, costs about 20/lb. Vanadium (99.9%) costs about 100/oz. 

Vanadium metal can be prepared either by the reduction of vanadium chloride with hydrogen or magnesium or by the reduction of vanadium oxide with calcium, aluminum, or carbon. The oldest and most commonly used method for producing vanadium metal on a commercial scale is the reduction of V20 with calcium. Recently, a two-step process involving the alurninotherniic reduction of vanadium oxide combined with electron-beam melting has been developed. This method makes possible the production of a purer grade of vanadium metal, ie, of the quaUty required for nuclear reactors (qv). 

Examination of the metallic product (regulus) of such aluminothermically produced vanadium metal reveals the presence of oxide phases in the metal matrix. This suggests that there is a decreasing solubiHty for aluminum and oxygen below the melting point. To date, no purification processes have been developed that take advantage of the purification potential of this phenomenon. 

Halides and Oxyhalides. Vanadium(V) oxytrichloride is prepared by chloriaation of V20 mixed with charcoal at red heat. The tetrachloride (VCl is prepared by chlorinating cmde metal at 300°C and freeing the Hquid from dissolved chlorine by repeated freezing and evacuation. It now is made by chlorinating V20 or VOCl ia the presence of carbon at ca 800°C. Vanadium trichloride (VCl ) can be prepared by heating VCl ia a stream of CO2 or by reaction of vanadium metal with HCl. 

Minor uses of vanadium chemicals are preparation of vanadium metal from refined pentoxide or vanadium tetrachloride Hquid-phase organic oxidation reactions, eg, production of aniline black dyes for textile use and printing inks color modifiers in mercury-vapor lamps vanadyl fatty acids as driers in paints and varnish and ammonium or sodium vanadates as corrosion inhibitors in flue-gas scmbbers. 

Vanadium (metal) [7440-62-2] M 50.9, m 1910°, d 6.0. Cleaned by rapid exposure consecutively to HNO3, HCl, HF, de-ionised water and reagent grade acetone, then dried in a vacuum desiccator. 

The usual extraction procedure is to roast the crushed ore, or vanadium residue, with NaCl or Na2C03 at 850°C. This produces sodium vanadate, NaV03, which is leached out with water. Acidification with sulfuric acid to pH 2-3 precipitates red cake , a polyvanadate which, on fusing at 700°C, gives a black, technical grade vanadium pentoxide. Reduction is then necessary to obtain the metal, but, since about 80% of vanadium produced is used as an additive to steel, it is usual to effect the reduction in an electric furnace in the presence of iron or iron ore to produce ferrovanadium, which can then be used without further refinement. Carbon was formerly used as the reductant, but it is difficult to avoid the formation of an intractable carbide, and so it has been superseded by aluminium or, more commonly, ferrosilicon (p. 330) in which case lime is also added to remove the silica as a slag of calcium silicate. If pure vanadium metal is required it can... 

The benefit of vanadium as an additive in steel is that it forms V4C3 with any carbon present, and this disperses to produce a finegrained steel which has increased resistance to wear and is stronger at high temperatures. Such steels are widely used in the manufacture of springs and high-speed tools. In 1995, world consumption of vanadium metal, alloys and concentrates exceeded 33 000 tonnes of contained vanadium. 

A sample of an oxide of vanadium weighing 4.589 g was heated with hydrogen gas to form water and another oxide of vanadium weighing 3.782 g. The second oxide was treated further with hydrogen until only 2.573 g of vanadium metal remained. 

One of the early applications of calcium as a reducing agent has been in the preparation of vanadium metal from vanadium pentoxide ... 

The form in which vanadium metal product is obtained is determined by the physicochemical conditions prevalent during reduction. This factor, elaborated below for vanadium production in ingot and powder forms, is typically illustrative of the calciothermy as... 

In practice, the production of vanadium by aluminothermic reduction is also governed by some other considerations. The reduction has to be carried out under an inert atmosphere (helium or argon) to avoid nitrogen pick-up from the air by vanadium metal. The composition of the oxide-aluminum charge has to be so chosen that the thermit (metal obtained by aluminothermic reduction) contains between 11 and 19% aluminum. This is necessary for the subsequent refining step in the vanadium metal production flowsheet. Pure vanadium pentoxide and pure aluminum are used as the starting materials, and the reduction is conducted in a closed steel bomb as shown in Figure 4.17 (C). 

Electrorefining Process for Vanadium Metal Extraction, Trans. Indian Inst Metals, Vol. 26, No. 6, p. 24, Dec. 1973. 

Sometime later in 1869, vanadium metal was isolated from its ores by Henry Enfield Roscoe (1833—1915), but Sefstrom had already received credit for the discovery of the element vanadium. 

Vanadium metal is prepared from pentoxide, V2O5, by reduction with calcium at elevated temperatures. Presence of iodine lowers calcium reduction temperature to 425°C because of heat of formation of calcium iodide. Pentoxide also may be converted to the trichloride, VCI3, and the trichloride reduced with magnesium metal or magnesium-sodium mixture at high temperatures to form high purity ductile metal. Alternatively, a fused mixture of vanadium chloride, sodium chloride, and hthium chloride may be electrolyzed to produce the metal in high purity. 

Vanadium pentoxide may be reduced to vanadium tetraoxide, trioxide, or vanadium metal by various reducing agents including hydrogen, carbon, and oxahc acid. Pentoxide may be reduced to metal by heating at high temperatures with calcium or magnesium. 

When he began his researches on vanadium, its compounds were listed at .35 per ounce, and the metal itself was unknown. After all attempts at direct reduction of the oxides had failed, Roscoe attempted to reduce vanadium dichloride, VC12, with hydrogen. Rigorous exclusion of oxygen and moisture was necessary, and, since vanadium metal reacts violently with glass and porcelain, the chloride was placed in platinum boats inside a porcelain tube. The tube itself could not be made of platinum because of the porosity of that metal at red heat. 

Vanadium predpitates the metal from solutions of salts of gold, silver, platinum, and iridium, and reduces solutions of mercuric chloride, cupric chloride and ferric chloride to mercurous chloride, cuprous chloride, and ferrous chloride, respectively. In these reactions the vanadium passes into solution as the tetravalent ion. No precipitation or reduction ensues, however, when vanadium is added to solutions of divalent salts of zinc, cadmium, nickel, and lead. From these reactions it has been estimated that the electrolytic potential of the change, vanadium (metal)—>-tetravalent ions, is about —0 3 to —0 4 volt, which is approximately equal to the electrolytic solution pressure of copper. This figure is a little uncertain through the difficulty of securing pure vanadium.5... 

The production of vanadium metal essentially is the calcium reduction ot vanadium pcntcixide in Ihc presence of iodine and is known its the McKechiiie-Seyboll process. The reaction is earned out in a steel bomb at about 7(K) C. The end products are vanadium metal, lime, and calcium iodide. A similar iodide process also is used in the production of high-purily zirconium. 

Since Weiss and DeMarco (91) detected the asphericity in charge distribution in vanadium metal, the 3d electron distributions in crystals of V, Cr, and Fe have been studied experimentally as well as theoretically (89). Crystals of V, Cr, and Fe are body-centered cubic at room temperature and under normal pressure. Charge asphericity has... 

Several generations of vanadium metal catchers have been developed (1, 2), leading to an improved activity retention at high vanadium levels on catalyst. The recent progress in nickel tolerance with new nickel encapsulation technologies is just as dramatic. 

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