Reduction sodium

The first commercial production of fatty alcohol ia the 1930s employed the sodium reduction process usiug a methyl ester feedstock. The process was used ia plants constmcted up to about 1950, but it was expensive, hazardous, and complex. By about 1960 most of the sodium reduction plants had been replaced by those employing the catalytic hydrogenolysis process. Catalytic hydrogenation processes were investigated as early as the 1930s by a number of workers one of these is described ia reference 26. 

The manufacture of refractory metals such as titanium, zirconium, and hafnium by sodium reduction of their haHdes is a growing appHcation, except for titanium, which is produced principally via magnesium reduction (109—114). Typical overall haHde reactions are... 

Sodium reduction processes are also described for tantalum (115), siHcon (116—118), magnesium (119), and other metals. 

Fig. 3. Schematic of a reactor used to produce tantalum powder by the sodium reduction process.

The dramatic improvements in the physical and chemical properties of tantalum powder produced by the sodium reduction process are evident in the lessening of chemical impurities (see Table 5). The much-improved chemistry reflects the many modifications to the process put in place after 1990. 

Post-Reduction Processing. The primary tantalum powder produced by the sodium reduction process is treated to convert the metal to a form suitable for use as capacitor-grade powder and feedstock for wire and sheet. 

Other Reductions. Ductile, pure zirconium has been made by a two-stage sodium reduction of zirconium tetrachloride (68) in which the tetrachloride and sodium are continuously fed into a stirred reactor to form zirconium dichloride [13762-26-0], heating with additional sodium yields zirconium metal. Leaching with water removes the sodium chloride from the zirconium. Bomb reduction of pure zirconium tetrafluoride with calcium also produces pure metal (69). 

Ion exchangers are sometimes used on a throwaway basis also. In the laboratoiy, ion exchangers are used to produce deionized water, purify reagents, and prepare inorganic sols. In medicine, they are used as antacid, for sodium reduction, for the sustained release of drugs, in skin-care preparations, and in toxin removal. 

Another application of tantalum strip solution is in the precipitation of potassium fluorotantalate, K2TaF7, which is used as a precursor in the production of tantalum powder by sodium reduction of melts. 

In the second part of the 20th century, the tantalum capacitor industry became a major consumer of tantalum powder. Electrochemically produced tantalum powder, which is characterized by an inconsistent dendrite structure, does not meet the requirements of the tantalum capacitor industry and thus has never been used for this purpose. This is the reason that current production of tantalum powder is performed by sodium reduction of potassium fluorotantalate from molten systems that also contain alkali metal halides. The development of electronics that require smaller sizes and higher capacitances drove the tantalum powder industry to the production of purer and finer powder providing a higher specific charge — CV per gram. This trend initiated the vigorous and rapid development of a sodium reduction process. 

For a long period of time, molten salts containing niobium and tantalum were widely used for the production by electrolysis of metals and alloys. This situation initiated intensive investigations into the electrochemical processes that take place in molten fluorides containing dissolved tantalum and niobium in the form of complex fluoride compounds. Well-developed sodium reduction processes currently used are also based on molten salt media. In addition, molten salts are a suitable reagent media for the synthesis of various compounds, in the form of both single crystals and powdered material. The mechanisms of the chemical interactions and the compositions of the compounds depend on the structure of the melt. 

The sodium reduction process was first implemented in Germany by Siemens and Halske A.G. and it remained a principally European method, while the American tantalum industry was founded exclusively on the electrolysis of molten fluorides [28, 576]. The production of tantalum by sodium reduction has gained worldwide acceptance and currently, nearly 90% of the world s tantalum is produced by the sodium reduction method [538]. 

The main reason for the tantalum industry s drive toward the sodium reduction process is an increasing demand for tantalum powder by tantalum capacitor manufacturers. The modem tendency of the electronics industry to miniaturize their components calls for the improvement of tantalum powder... 

Gruner, Ibold and Naumann [589] proposed the performance of thermal treatment of the cake obtained after sodium reduction of K2TaF7 in vacuum. The application of a temperature of 800-1050°C and a residual pressure of 0.013-1.33 Pa was recommended. The process is performed with intermittent vibration in order to promote the separation of the impurities. It is reported that the resulting tantalum contains 31 and 40 ppm of Na and K, respectively. 

The main metallic impurities that contaminate the primary powder, due to chemical corrosion of the retort and other metal parts of the reactor, are Fe, Ni and Cr. From this point of view, reactors that are equipped with larger retorts usually provide better purity due to a relatively low ratio between the internal surface of the wet metal parts of the reactor and the total volume of the melt. Recent investigations on the decreasing of Fe, Ni and Cr impurities during the sodium reduction process were performed by Li [591]. It was shown that one of the most effective ways to reduce contamination of the product is to reduce the duration of time K2TaF7 is present in the reactor. 

Chai and Zhong [602] investigated the melting properties of molten systems containing K2TaF7 and different alkali metal cations with respect to the optimization of the sodium reduction process. It was shown that the specific... 

Sodium reduction development directions, 336 diluted melts, 331-332 of K-Salt, 327-328 principals, 326 Solid-phase interaction mechanism, 34-37 niobium oxyfluorides, 26-31 tantalum oxyfluorides, 32-34 Solubility diagrams (NH4)5Nb3OF18, 22 K2NbF7 in HF solutions, 14 K2TaF7 in HF solutions, 14 RbsNbjOF,, 22-23 Solubility of peroxides, 307 Specific conductivity, 153, 164 Spontaneous polarization, 223 Structural characteristics for X Me=8, 61,... 

Modem refining technology uses tantalum and niobium fluoride compounds, and includes fluorination of raw material, separation and purification of tantalum and niobium by liquid-liquid extraction from such fluoride solutions. Preparation of additional products and by-products is also related to the treatment of fluoride solutions oxide production is based on the hydrolysis of tantalum and niobium fluorides into hydroxides production of potassium fluorotantalate (K - salt) requires the precipitation of fine crystals and finishing avoiding hydrolysis. Tantalum metal production is related to the chemistry of fluoride melts and is performed by sodium reduction of fluoride melts. Thus, the refining technology of tantalum and niobium involves work with tantalum and niobium fluoride compounds in solid, dissolved and molten states. 

Columbium (also known as niobium) and tantalum metals are produced from purified salts, which are prepared from ore concentrates and slags resulting from foreign tin production. The concentrates and slags are leached with hydrofluoric acid to dissolve the metal salts. Solvent extraction or ion exchange is used to purify the columbium and tantalum. The salts of these metals are then reduced by means of one of several techniques, including aluminothermic reduction, sodium reduction, carbon reduction, and electrolysis.19-21 Owing to the reactivity of these metals, special techniques are used to purify and work the metal produced. 

Hunt SC, Cook NR, Oberman A, Cutler JA, Hennekens CH, Allender PS, Walker WG, Whelton PK, Williams RR. Angiotensinogen genotype, sodium reduction, weight loss, and prevention of hypertension - trials of Hypertension Prevention, Phase II. Hypertension 1998 32 393-401. 

Titanium (IV) iodide may be prepared by a variety of methods. High-temperature methods include reaction of titanium metal with iodine vapor,1-3 titanium carbide with iodine,4 titanium(IV) oxide with aluminum (III) iodide,5 and titanium (IV) chloride with a mixture of hydrogen and iodine. At lower temperatures, titanium (IV) iodide has been obtained by the combination of titanium and iodine in refluxing carbon tetrachloride7 and in hot benzene or carbon disulfide 8 a titanium-aluminum alloy may be used in place of titanium metal.9 It has been reported that iodine combines directly with titanium at room temperature if the metal is prepared by sodium reduction of titanium (IV) chloride and is heated to a high temperature before iodine is... 

Lin P-H, Ginty F, Appel L, Aickin M, Bohannon A, Gamero P, Barcaly D and Svetkey L. 2003. The DASH diet and sodium reduction improve markers of bone turnover and calcium metabolism in adults. 

In contrast, the sodium complex [Na(AsPh2)(dioxane)]x is polymeric in the solid state [Na-As = 2.962(4), 2.937(4) A] (25). This complex was synthesized by the rather unusual method of sodium reduction of a diarsine ... 

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