Vanadium pentoxide with sodium chlorate

Fumaric acid is conveniently prepared by the oxidation of the inexpensive furfural with sodium chlorate in the presence of a vanadium pentoxide catalyst ... 

Benzoquinone ( quinone ) is obtained as the end product of the oxidation of aniline by acid dichromate solution. Industrially, the crude product is reduced with sulphur dioxide to hydroquinone, and the latter is oxidised either with dichromate mixture or in very dilute sulphuric acid solution with sodium chlorate in the presence of a little vanadium pentoxide as catalyst. For the preparation in the laboratory, it is best to oxidise the inexpensive hydroquinone with chromic acid or with sodium chlorate in the presence of vanadium pent-oxide. Naphthalene may be converted into 1 4-naphthoquinone by oxidation with chromic acid. 

By oxidizing butyl alcohol with sodium chlorate and dilute sulfuric add, using vanadium pentoxide as a catalyst. Milas, J. Amer. Chem. Soc. 50, 493 (1928). 

Oxidation. Milas developed a procedure for the preparation of fumaric acid by oxidation of furfural with sodium chlorate catalyzed by vanadium pentoxide. A mixture of sodium chlorate, 1 1. of water, and 2 g, of vanadium pentoxide is... 

C. Fumaric acid from furfural. Place in a 1-litre three-necked flask, fitted with a reflux condenser, a mechanical stirrer and a thermometer, 112 5 g. of sodium chlorate, 250 ml. of water and 0 -5 g. of vanadium pentoxide catalyst (1), Set the stirrer in motion, heat the flask on an asbestos-centred wire gauze to 70-75°, and add 4 ml. of 50 g. (43 ml.) of technical furfural. As soon as the vigorous reaction commences (2) bvi not before, add the remainder of the furfural through a dropping funnel, inserted into the top of the condenser by means of a grooved cork, at such a rate that the vigorous reaction is maintained (25-30 minutes). Then heat the reaction mixture at 70-75° for 5-6 hours (3) and allow to stand overnight at the laboratory temperature. Filter the crystalline fumaric acid with suction, and wash it with a little cold water (4). Recrystallise the crude fumaric acid from about 300 ml. of iif-hydrochloric acid, and dry the crystals (26 g.) at 100°. The m.p. in a sealed capillary tube is 282-284°. A further recrystaUisation raises the m.p. to 286-287°. 

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). 

In a 5-I. flat-bottom flask, equipped with a condenser (Note 1), a separatory funnel and a mechanical stirrer (Note 2), are placed 450 g. (2.24 moles) of sodium chlorate, 2 g. of vanadium pentoxide (Note 3) and 1 1. of water. The mixture is heated (Note 4) to 70-750 by supporting the flask to cm. above an electric hot plate. To the well-stirred solution is then added 200 g. (2.06 moles) of furfural (Note 5) over a period of seventy to eighty minutes. After the addition of furfural is complete, the mixture is heated at 70-75°, with stirring, for ten to eleven hours, and then allowed to stand at room temperature overnight. The mixture is filtered by suction, and the crude fumaric acid is dried in the air. The yield is 155-170 g. (65-72 per cent of the theoretical amount) (Note 6). 

In a 2-1. round-bottomed flask equipped with a mechanical stirrer are placed 11. of 2 per cent sulfuric acid, 0.5 g. of vanadium pentoxide (Note i), no g. (i mole) of hydroqiunone, and 60 g. (0.56 mole) of sodium chlorate. The mixture is vigorously stirred for about three hours, when the green quinhydrone first formed is converted to yellow quinone. The temperature of the reaction mixture rises to about 40° (Note 2). The reaction is usually complete in three and one-half to four hours. The flask is then disconnected and cooled under the tap, the mixture is filtered with suction, and the quinone is washed once with about 100 cc. of cold water. After drying in a desiccator over calcium chloride, the product weighs 86-90 g. and melts at 110-112°. This material is pure enough for most purposes. Extraction of the filtrate and washings with four loo-cc. portions of benzene yields a further 12-14 g- of quinone, and brings the total amount to gg-104 g. (92-96 per cent of the theoretical yield) (Note 3). 

Other oxidizing agents have been used. Sodium chlorate with vanadium pentoxide catalyst attacks anthracene readily but is not powerful enough for the conversion of hydrocarbons of the naphthalene and phenanthrene series. An acetic acid solution of 30% hydrogen peroxide has also been used. °... 

Derivatives of phenol or aniline can be oxidized to quinones, the yield and ease of oxidation depending on the substituents. If an amino or hydroxyl group is in the para position, the reaction proceeds readily, as illustrated by the synthesis of quinone from hydroquinone by oxidation with a sodium chlorate-vanadium pentoxide mixture (5>6%) or with chromic-sulfuric acid mixture (92%). A para halogen atom usually has a favorable effect. Any group in the para position is eliminated or oxidized. o-Quinones are usually prepared from the corresponding catechols. A survey of procedures for the synthesis of benzoquinones by oxidation has been made. ... 

With vanadium pentoxide as catalyst in an acidic medium, sodium chlorate oxidizes hydroquinone to quinone. A procedure by Underwood and Walsh calls for stirring a mixture of the reactants in 1 I. of 2% sulfuric acid until the green... 

Graebe and Liebermann378 converted anthracene into anthraquinone by oxidation with chromic acid in glacial acetic acid, although it is preferable379 to use sodium chlorate and vanadium pentoxide as catalysts. However, anthraquinone can also be prepared in good yield by use of potassium permanganate ... 

Stratcor process (Durango, CO). In Durango, US Vanadium Corp. recovers vanadium as a coproduct with uranium by leaching the ore concentrate for 24 h with hot sulfuric acid and an oxidant such as sodium chlorate (NaClOj). After removal of solids, the leachate is fed into a solvent-extraction circuit, where the uranium is extracted in an organic solvent consisting of 2.5%-amine-2.5%-isodecanol-95%-kerosene. Vanadium remains in the raffinate, which is fed into a second solvent-extraction circuit. There vanadium in turn is extracted in the organic phase, stripped with a 10 wt.% soda-ash solution, and precipitated with ammonium sulfate. The ammonium metavanadate precipitate is filtered, dried, and calcined to yield flakes of black (fused) vanadium pentoxide. 

---