Molybdic oxide

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). 

Molybdenum trioxide is a condensed-phase flame retardant (26). Its decomposition products ate nonvolatile and tend to increase chat yields. Two parts of molybdic oxide added to flexible poly(vinyl chloride) that contains 30 parts of plasticizer have been shown to increase the chat yield from 9.9 to 23.5%. Ninety percent of the molybdenum was recovered from the chat after the sample was burned. A reaction between the flame retardant and the chlorine to form M0O2 012 H20, a nonvolatile compound, was assumed. This compound was assumed to promote chat formation (26,27). 

Molybdenite concentrate contains about 90% M0S2. The remainder is primarily siUca, with lesser amounts of Fe, Al, and Cu. The concentrate is roasted to convert the sulfide to technical molybdic oxide. Molybdenum is added to steel in the form of this oxide. In modem molybdenum conversion plants, the oxidized sulfur formed by roasting M0S2 is converted to sulfuric acid. 

Technical molybdic oxide can be reduced by reaction of ferrosiUcon in a thermite-type reaction. The resulting product contains about 60% molybdenum and 40% iron. Foundries generally use ferromolybdenum for adding molybdenum to cast iron and steel, and steel mills may prefer ferromolybdenum to technical molybdic oxide for some types of steels. 

Molybdau-kies, m. molybdenite, -ocker, m. molybdic ocher, molybdite. -oxyd, n. molybdenum oxide (specif., one higher than MojOa). -oxydul, n. molybdous oxide (MoO, also MojOa). 

Spray plates with (1) 0.1% 2, 7 -dichloroflnorescein, (2) 1% AICI3 in ethanol, (3) 1% aqneons FeClj solution warm the plates to about 45°C briefly between sprays Prepare solution 1 4% solution of molybdic oxide in 70% H2SO4 add 0.4-g powdered molybdenum to 100 ml of solution 1 add 200-ml HjO and filter final spray consists of 100 ml of preceding and 200 ml HjO and 240-ml acetic acid... 

Calcium Molybdic oxide-molybdate carbon briquettes... 

A. K. Suri and C. K. Gupta, Electrolytic Recovery of Molybdenum from Molybdic Oxide and Molybdenum Sesquisulfide, Metall. Trans. B, Vol. 6B, p. 453,1975. 

This type of pigment is the precipitate formed when molybdic oxide is dissolved in aqueous sodium hydroxide with the addition of sodium chromate. The resulting mixture is reacted with a solution of lead nitrate. The precipitate formed is further processed through filtration, washing, drying, milling, and packaging. 

Molybdenum supplements, 17 40 Molybdenum trihalides, 17 26 Molybdenum trioxide, 17 9, 20 Molybdenum wire, manufacture of, 17 9 Molybdic oxide, 17 9... 

Synonyms molybdenum trioxide molybdic acid anhydride molybdic anhydride molybdic oxide... 

Laboratory investigation revealed that sodium, which was present in the support to the extent of several tenths of 1%, had a profound effect on stability and activity of the moiybdena-alumina catalyst. Over a period of time it was possible to alter the procedure for preparing the support on successive occasions until the catalyst contained much less than 0.1% sodium oxide. The reduction in sodium content of the support was immediately reflected in improved catalyst life. Ultimately the life was extended to 9 to 12 months before replacement. Various forms of alumina have been used as a support, including alumina gel and a stabilized alumina gel. Moiybdena-alumina catalyst has been employed exclusively in the eight commercial plants previously referred to. Today the majority of refiners who operate hydroformers are using molybdena on alumina gel as a catalyst. The molybdic oxide content of the catalyst is somewhat below 10%. Although similar to the original catalyst as far as chemical composition is concerned, it possesses superior activity and life. 

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. 

Molybdenum salts used as catalysts include cobalt molybdate for hydrogen treatment of petroleum stocks for desulfurization, and phospho-molybdates to promote oxidation. Compounds used for dyes are sodium, potassium, and ammonium molybdates. With basic dyes, phosphomolyb-dic acid is employed. The pigment known as molybdenum orange is a mixed crystal of lead chromate and lead molybdate. Sodium molybdate, or molybdic oxide, is added to fertilizers as a beneficial trace element. Zinc and calcium molybdate serve as inhibitory pigments in protective coatings arid paint for metals subjected to a corrosive atmosphere. Compounds used to produce better adherence of enamels are molybdenum trioxide and ammonium, sodium, calcium, barium, and lead molybdates. 

Several of the reactions listed under type reactions are not possible to calculate because of the lack of available information. Decomposition and formation of hydrides and nitrides can, respectively, lead to the evolution and disappearance of hydrogen or nitrogen. The removal of adsorbed gas from the surface, from grain boundaries, or from the lattice is important but not amenable to calculation. The volatilization of the oxides, with the exception of molybdic oxide, is also impossible to calculate because of the lack of data. 

By-product processing is also largely by crushing and flotation, but the flotation processes are more specialised because of the variety of ores involved and the need to separate the small molybdenum content from the major proportion of copper or other primary metals. Because the product is mainly used in steelmaking, oxidation to molybdic oxide is acceptable, and an intermediate roasting may also be used. 

Typical analyses of three commercial powders are shown in Table 2.3 . They differ mainly in that the fine grinding of the Superfine powder increased the acidity and ailowed it to pick up some oii and water contamination. The acid insoiubies include siliceous material, and these may possibly be abrasive, but there is no direct correlation between silica content and abrasiveness. The molybdic oxide, formed by oxidation of molybdenum disulphide, is less abrasive than most technical grades of the disulphide itself, as shown in Table 2.4 and it is only the... 

The bulk of the concentrate separated from molybdenite ore by flotation is further processed to produce molybdenum. A typical extraction and purification procedure is outlined in Figure 2.1. The concentrate is roasted to convert the moiybdenum disulphide to molybdic oxide. The product is called roasted concentrate, and about 30% is marketed as Technical Oxide, mainly for alloy manufacture. A typical range of compositions is shown in Table 2.6. 

Purified molybdic oxide is produced by volatilisation in a stream of air in sand-hearth furnaces at about 1200°C. Molybdic oxide melts at 795°C, but its vapour pressure is very high, and the volatilisation process is sometimes referred to as sublimation rather than distillation. The product is a fine powder containing from 99.5% to 99.97% of molybdenum trioxide. 

Ammonium molybdate is manufactured by dissolving technical molybdic oxide in hot ammonia. It can be highly purified to over 99.9% purity, and... 

Table 2.6 Typical Composition of Technical Molybdic Oxide...

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