Salt solutions molybdenum

Inorganic salt solutions Molybdenum has excellent resistance to 3% sodium chloride, 10% aluminium chloride and 10% ammonium chloride at temperatures up to 100°C. It is severely corroded by 20% solutions of ferric and cupric chlorides at 35°C and is subject to pinhole-type pitting in mercuric chloride solutions (Table 5.5). 

The catalysts are prepared by impregnating the support with aqueous salts of molybdenum and the promoter. In acidic solutions, molybdate ions are present largely in the form of heptamers, [Mo2024] , and the resulting surface species are beHeved to be present in islands, perhaps containing only seven Mo ions (100). Before use, the catalyst is treated with H2 and some sulfur-containing compounds, and the surface oxides are converted into the sulfides that are the catalyticaHy active species. 

Discussion. In acid solution, toluene-3,4-dithiol (dithiol) forms a red compound when warmed with tin(II) salts (compare molybdenum, Section 17.30). Tin(IV) also reacts, but more slowly than tin(II) thioglycollic acid may be employed to reduce tin(IV) to tin(II). The reagent is not stable, being easily reduced, and hence should be prepared as required. A dispersant is generally added to the solution under test. 

Molybdenum/zeolite catalysts prepared by impregnating zeolites with ammonium hepiamolybdate solution generally give rise to poor dispersion of molybdenum [2]. In contrast, ion exchange would be an ideal method for loading active metal species onto supports. Few cationic forms are available as simple salts of molybdenum of high oxidation... 

Normal molybdates are prepared by two methods (1) precipitating the insoluble metal molybdates obtained by adding the salt solution of the desired metal to a solution of sodium or potassium molybdate, and (2) neutrahzing a slurry or solution of molybdenum trioxide with the hydroxide or carbonate of the desired metal. For example, sodium molybdate, Na2Mo04, may be obtained as a dihydrate by evaporating an aqueous solution of molybdenum trioxide and sodium hydroxide. Heating the dihydrate at 100°C converts it to the anhydrous salt. Also, the normal molybdates of certain metals can be prepared by fusion of molybdenum trioxide with the desired metal oxide. 

Initially tests were conducted in glass equipment at atmospheric pressure. It was discovered that a more durable catalyst could be made if the Group VI metal oxide were deposited on an alumina support. The best support found for this reaction was alumina, and the first commercial catalyst was made by impregnating a material very similar to activated alumina 1 with a molybdenum salt solution, followed by drying and calcining at a temperature above 1000° F. Interestingly enough, the supported chromia catalyst which showed a marked superiority over the supported molybdena catalyst at atmospheric... 

The salts are strong reducing agents. If a solution of iron (III) chloride in hydrochloric acid is added to a solution of either of the salts, the molybdenum is oxidized, as is evidenced by a reversal of the color changes observed during the electrolytic reduction of molybdic acid. 

Very recently Geus and co-workers [44, 45] have applied another method based on chemical complexes. This is the complex cyanide method to prepare both monocomponent (Fe or Co) and multicomponent Fischer-Tropsch catalysts. A large range of insoluble complex cyanides are known in which many metals can be combined, e.g. iron(n) hexacyanide and iron(m) hexacyanide can be combined with iron ions, but also with nickel, cobalt, copper, and zinc ions. Soluble complex ions of molybdenum(iv) which can produce insoluble complexes with metal cations are also known. Deposition precipitation (Section A.2.2.1.5) can be performed by injection of a solution of a soluble cyanide complex of one of the desired metals into a suspension of a suitable support in a solution of a simple salt of the other desired metal. By adjusting the cation composition of the simple salt solution, with a same cyanide, it is possible to adjust the composition of the precursor from a monometallic oxide (the case when the metallic cation is identical to that contained in the complex) to oxides containing one or several foreign elements. 

The validity of the description of this patented procedure was also challenged on the grounds that molybdic oxide needs to be present in the plated film for the conversion to take place. It is interesting, therefore, that C E Vest introduced an important modification to the process in order to electrodeposit molybdenum trioxide instead of molybdenum metal when studying the application of the technique to the lubrication of spacecraft components. Vest s modification was to use a mixed plating bath of molybdenum trioxide in an alkali salt solution such as ammonium formate. The component being coated formed the cathode, and the molybdenum was probably present in the bath in the form of ammonium molybdate. 

Alloys.1—The most important alloy of molybdenum is ferro-molybdenum, which is used as an addition to steel. The effect of molybdenum on steel is similar to that of tungsten, but is more marked the tensile strength is increased and the elastic limit raised. For highspeed tool-steels molybdenum is often used in conjunction with tungsten. It has been found that the addition of molybdenum in small quantities (up to 15 per cent.) to steel increases the liability to corrosion, especially in acid and salt solutions. An important use of steels containing 3 to 4 per cent, of molybdenum and 1-0 to 1-5 per cent, of carbon is for the manufacture of permanent magnets. ... 

The horohydride reduction of a nickel salt solution containing small amounts of other metal salts can lead to co-reduced mixed metal borides that frequently have enhanced catalytic properties when compared to the unmodified nickel boride. The presence of about 2% chromium significantly increased the activity of a P-1 nickel boride toward aldehyde hydrogenation. Molybdenum, tungsten and vanadium modifiers were somewhat less effective than chromium while the presence of a small amount of cobalt had an inhibiting effect on the reaction.22 As the data in Fig. 12.2 show, the amount of chromium responsible for optimum P-1 nickel boride activity depends on the substrate being hydrogenated.39... 

Fused salt solutions may be found in which the solubility of these oxides is appreciable at high temperatures and from which crystals grow as the solution is cooled. Some of the fluxes which have been used for growth of the oxides of concern here are (a) potassium nitrate-sodium nitrate, (b) lead fluoride-bismuth oxide, (c) lead oxide-bismuth oxide, and (d) lithium hydroxide-boric acid-molybdenum oxide. Temperatures frequently are in the range of 1300°C. 

The reduction of molybdate salts in acidic solutions leads to the formation of the molybdenum blues (9). Reductants include dithionite, staimous ion, hydrazine, and ascorbate. The molybdenum blues are mixed-valence compounds where the blue color presumably arises from the intervalence Mo(V) — Mo(VI) electronic transition. These can be viewed as intermediate members of the class of mixed oxy hydroxides the end members of which are Mo(VI)02 and Mo(V)0(OH)2 [27845-91-6]. MoO and Mo(VI) solutions have been used as effective detectors of reductants because formation of the blue color can be monitored spectrophotometrically. The nonprotonic oxides of average oxidation state between V and VI are the molybdenum bronzes, known for their metallic luster and used in the formulation of bronze paints (see Paint). 

Arsonium salts have found considerable use in analytical chemistry. One such use involves the extraction of a metal complex in aqueous solution with tetraphenyiarsonium chloride in an organic solvent. Titanium(IV) thiocyanate [35787-79-2] (157) and copper(II) thiocyanate [15192-76-4] (158) in hydrochloric acid solution have been extracted using tetraphenyiarsonium chloride in chloroform solution in this manner, and the Ti(IV) and Cu(II) thiocyanates deterrnined spectrophotometricaHy. Cobalt, palladium, tungsten, niobium, and molybdenum have been deterrnined in a similar manner. In addition to their use for the deterrnination of metals, anions such as perchlorate and perrhenate have been deterrnined as arsonium salts. Tetraphenyiarsonium permanganate is the only known insoluble salt of this anion. 

Samples were tested on in a melt of salts (75% Na SO, 25% NaCl) at 950°C in an air atmosphere for 24 hours. Micro X-rays spectrum by the analysis found that the chemical composition of carbides of an alloy of the ZMI-3C and test alloys differs noticeably. In the monocarbide of phase composition of an alloy of the ZMI-3C there increased concentration of titanium and tungsten is observed in comparison with test alloys containing chemical composition tantalum. The concentration of more than 2% of tantalum in test alloys has allowed mostly to deduce tungsten from a mono carbide phase (MC) into solid solution. Thus resistance of test alloys LCD has been increased essentially, as carbide phase is mostly sensitive aggressive environments influence. The critical value of total molybdenum and tungsten concentration in MC should not exceed 15%. 

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