Vanadium metal preparation

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). 

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. 

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

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. 

Note that very little pure vanadium metal is prepared commercially. However, the iron-vanadium alloy obtained by reduction with carbon of a mixture of the two oxides is used in large quantity in the steel... 

Vanadium(V) oxide, V2O5, a yellow, amphoteric solid, may be obtained as an intermediate in the preparation of vanadium metal, as indi-... 

Vanadium Triiodide. VI3 can be prepared by reaction of vanadium metal with iodine at elevated temperatures. It is a brownish-black, hygroscopic crystalline powder, soluble in most nonpolar solvents, that begins to dissociate into VI2 and I2 at 270 °C.i... 

Depending on whether vanadium is vaporized resistively or by means of an electron beam, the experimental procedures for metal preparation and deposition are sufficiently different that each merits a separate treatment. The type of apparatus used is a rotary reactor of the Torrovap design (Fig. 2). 

The asymmetric 1,4-addition (Michael addition) of a cyanide ion to nitroalkenes is a potentially useful route for preparing p-amino acids via transformation of 3-nitropropanonitriles. ° In 2013, North reported the first vanadium-catalysed, enantioselective Michael addition of trimethylsilyl cyanide to aliphatic p-nitroalkenes, which provided (S)-19, as shown in Scheme 9.9. The reaction was promoted by a 3 mol% catalyst loading of chiral vanadium(v) salen complex 18 ° providing (S)-19 in 74-88% conversions with up to 89% enantiomeric excess. North proposed that the nitro group acts as a bridge for the two vanadium metals in the possible transition... 

VC powder is prepared by the reaction of vanadium oxide or ammonium vanadate with carbon at 1500-1700 C in hydrogen followed by a vacuum heat treatment. The reaction of vanadium metal with carbon under vacuum is also used. VC coatings are deposited by CVD, evaporation or sputtering (see Clusters 14 and IS). 

Discovery In 1801, A. M. Del Rio in Mexico discovered a new metal in a brown lead ore. He gave the new element the name en/thronium. When confirmation was sought in Europe the metal was said to be chromium and the discovery was not accepted. In 1830, N. G. Sefetrom in Sweden discovered vanadium in iron, manufactured from an ore in Smalands-Taberg. F. Wohler in Germany showed that erythronium and vanadium are in fact identical. Sir Henry Roscoe prepared pure vanadium metal in 1867. His method was reduction of vanadium chloride with hydrogen. 

Throughout the whole period of discovery, the first three decades of the 19 century, vanadium minerals had been found and vanadium compounds been prepared. The metal itself, however, had not been isolated. BerzeHus showed early that it was impossible to prepare vanadium metal by reduction of the oxide with carbon. This gave vanadium carbide. Nor did reduction with metaUic potassium give the pure metal. 

Another group of initiator systems are metal halides (e.g., ZrC, TiCl4, etc.) and metallic oxyhalides (e.g., vanadium oxychloride) prepared on silica gel such as Cab-O-Sil (with a surface OH content of ca. 1.5mEq/g) or on a carbon black such as channel black or furnace black [492,513]. NVP and i-BusAl are added to a toluene slurry of this material. The reaction mixture is heated up to 80°C to yield 25% of PVP [513]. The polymerization initiated by carbon black at room temperature was totally inhibited by pyridine and DMF, which indicates the cationic nature of the reaction [514]. The polymerization rate is first order in carbon black [492]. The activation energy of the polymerization was determined to be 85 kJ/mol from an Arrhenius plot [514]. 

Early catalysts for acrolein synthesis were based on cuprous oxide and other heavy metal oxides deposited on inert siHca or alumina supports (39). Later, catalysts more selective for the oxidation of propylene to acrolein and acrolein to acryHc acid were prepared from bismuth, cobalt, kon, nickel, tin salts, and molybdic, molybdic phosphoric, and molybdic siHcic acids. Preferred second-stage catalysts generally are complex oxides containing molybdenum and vanadium. Other components, such as tungsten, copper, tellurium, and arsenic oxides, have been incorporated to increase low temperature activity and productivity (39,45,46). 

Oxidation of methanol to formaldehyde with vanadium pentoxide catalyst was first patented in 1921 (90), followed in 1933 by a patent for an iron oxide—molybdenum oxide catalyst (91), which is stiU the choice in the 1990s. Catalysts are improved by modification with small amounts of other metal oxides (92), support on inert carriers (93), and methods of preparation (94,95) and activation (96). In 1952, the first commercial plant using an iron—molybdenum oxide catalyst was put into operation (97). It is estimated that 70% of the new formaldehyde installed capacity is the metal oxide process (98). 

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