Ammonium molybdate oxidation

Hydrogen peroxide/ammonium molybdate Oxidation of sugar mercaptals... 

Molybdenum Oxides. Molybdenum was one of the first elements used to retard the flames of ceUulosics (2). Mote recently it has been used to impart flame resistance and smoke suppression to plastics (26). Molybdic oxide, ammonium octamolybdate, and zinc molybdate ate the most widely used molybdenum flame retardants. Properties ate given in Table 5. These materials ate recommended almost exclusively for poly(vinyl chloride), its alloys, and unsaturated polyesters (qv). 

Chemical products are produced from technical-grade oxide in two very different ways. Molybdenum trioxide can be purified by a sublimation process because molybdenum trioxide has an appreciable vapor pressure above 650°C, a temperature at which most impurities have very low volatiUty. The alternative process uses wet chemical methods in which the molybdenum oxide is dissolved in ammonium hydroxide, leaving the gangue impurities behind. An ammonium molybdate is crystallized from the resulting solution. The ammonium molybdate can be used either directly or thermally decomposed to produce the pure oxide, MoO. ... 

In this process, catalysts, such as boric acid, molybdenum oxide, zirconium, and titanium tetrachloride or ammonium molybdate, are used to accelerate the reaction. The synthesis is either carried out in a solvent (aUphatic hydrocarbon, trichlorobenzene, quinoline, pyridine, glycols, or alcohols) at approximately 200°C or without a solvent at 300°C (51,52). 

The reaction velocity is comparatively slow, but increases with increasing concentration of acid. The addition of three drops of a neutral 20 per cent ammonium molybdate solution renders the reaction almost instantaneous, but as it also accelerates the atmospheric oxidation of the hydriodic acid, the titration is best conducted in an inert atmosphere (nitrogen or carbon dioxide). 

Molybdenum blue method. When arsenic, as arsenate, is treated with ammonium molybdate solution and the resulting heteropolymolybdoarsenate (arseno-molybdate) is reduced with hydrazinium sulphate or with tin(II) chloride, a blue soluble complex molybdenum blue is formed. The constitution is uncertain, but it is evident that the molybdenum is present in a lower oxidation state. The stable blue colour has a maximum absorption at about 840 nm and shows no appreciable change in 24 hours. Various techniques for carrying out the determination are available, but only one can be given here. Phosphate reacts in the same manner as arsenate (and with about the same sensitivity) and must be absent. 

The solvent process involves treating phthalonitrile with any one of a number of copper salts in the presence of a solvent at 120 to 220°C [10]. Copper(I)chloride is most important. The list of suitable solvents is headed by those with a boiling point above 180°C, such as trichlorobenzene, nitrobenzene, naphthalene, and kerosene. A metallic catalyst such as molybdenum oxide or ammonium molybdate may be added to enhance the yield, to shorten the reaction time, and to reduce the necessary temperature. Other suitable catalysts are carbonyl compounds of molybdenum, titanium, or iron. The process may be accelerated by adding ammonia, urea, or tertiary organic bases such as pyridine or quinoline. As a result of improved temperature maintenance and better reaction control, the solvent method affords yields of 95% and more, even on a commercial scale. There is a certain disadvantage to the fact that the solvent reaction requires considerably more time than dry methods. 

Ammonium molybdate is prepared by treating molybdenum oxide with excess ammonia in an aqueous solution. The crystals are obtained after evaporation of water. 

Elemental composition H 4.58%, P 46.94%, O 48.49%. The hypophosphite ion may he oxidized to orthophosphate by careful oxidation. The orthophophate, PO4 ion, may he measured by colorimetry either hy using ammonium molybdate and vanadium (yellow color), ammonium molybdate and stannous chloride (blue color), or ammonium molybdate, potassium anti-monyl tartrate and asorbic acid (an intense blue color). Absorbances of the solution are read at 400 (or 470), 650 (or 690) and 880 nm, respectively. Hypophosphite ion alternatively may be identified by ion chromatography. 

Alternatively, the oxide may be prepared by heating a molybdate salt, such as ammonium molybdate, with a reducing agent such as zinc. The dioxide also may be obtained along with other oxides of molybdenum when molybdenum metal is heated in air. 

Purified molybdenum (VI) oxide also is made by prolonged heating of ammonium molybdate in air ... 

An alternative method involves repeatedly evaporating a mixture of ammonium molybdate and nitric acid. Ammonium nitrate so formed is separated from the product molybdenum(VI) oxide by extraction with water ... 

An early attempt to deposit Mo—S on various metal substrates using ammonium molybdate and thiosulphate resulted in films that were found to be sulphur free and believed to be an oxide, although this was not investigated further [35]. 

Pour 2-3 ml of a 10 % nitric acid solution into 2-3 ml of a 20 % ammonium molybdate solution. What substance precipitates What is its colour Wash the precipitate with water by decantation and divide it into two parts. React one part of the precipitate with an excess of concentrated hydrochloric acid and the other with a 20% sodium hydroxide solution. Explain the results. Write the equations of the reactions. Under what conditions does molybde-num(Vl) oxide dihydrate form ... 

Preparation of Molybdenum(VI) Oxide, a. Preparation of Molybdenum(VI) Oxide by the Thermal Decomposition of Ammonium Molybdate. Put a boat with 0.5 g of ammonium molybdate into a porcelain tube in an electric furnace. Connect one end of the... 

Preparation of Materials and Samples. The source of the molybdenum oxide vapor was M0O3 containing "Mo tracer. The "Mo was supplied as ammonium molybdate in NH4OH solution (Nuclear Science and Engineering Co.). The solution was evaporated to dryness in a platinum crucible, and the ammonium molybdate was heated in air at about 500°C. for several hours to decom ose it to M0O3. 

Phosphates. — Slake 3 gm. of calcium oxide with 10 cc. of water, dissolve in 25 cc. of nitric acid, and add 25 cc. of ammonium molybdate solution. No yellow precipitate should form on standing twelve hours at 30 to 403 C. 

Pure molybdic oxide (99.95% MnO.O is prepared by sublimation of technical oxide or by calcining ammonium molybdate. Metallic molybdenum powder is prepared commercially by hydrogen reduction of either pure molybdic oxide ctr ammonium molybdate in a two-step process. The first step, carried out at about 500 C yields MoO-. The second step, reduction of M0O2 to Mo, is carried out al about I 00°C. 

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