Reduction titanium purification

Aluminum. All primary aluminum as of 1995 is produced by molten salt electrolysis, which requires a feed of high purity alumina to the reduction cell. The Bayer process is a chemical purification of the bauxite ore by selective leaching of aluminum according to equation 35. Other oxide constituents of the ore, namely siUca, iron oxide, and titanium oxide remain in the residue, known as red mud. No solution purification is required and pure aluminum hydroxide is obtained by precipitation after reversing reaction 35 through a change in temperature or hydroxide concentration the precipitate is calcined to yield pure alumina. 

Other Metals. AH the sodium metal produced comes from electrolysis of sodium chloride melts in Downs ceUs. The ceU consists of a cylindrical steel cathode separated from the graphite anode by a perforated steel diaphragm. Lithium is also produced by electrolysis of the chloride in a process similar to that used for sodium. The other alkaH and alkaHne-earth metals can be electrowon from molten chlorides, but thermochemical reduction is preferred commercially. The rare earths can also be electrowon but only the mixture known as mischmetal is prepared in tonnage quantity by electrochemical means. In addition, beryIHum and boron are produced by electrolysis on a commercial scale in the order of a few hundred t/yr. Processes have been developed for electrowinning titanium, tantalum, and niobium from molten salts. These metals, however, are obtained as a powdery deposit which is not easily separated from the electrolyte so that further purification is required. 

The method based on the precipitation of peroxometalate precursors enables to achieve additional purification during the process. Thus, the addition of complexonates, such as OEDP or EDTA, which form stable complexes with some polyvalent metals, prevents co-precipitation of the main impurities such as Fe, Co, Ni, Mn, Mg, etc., which in turn significantly increases the purity of the final product. Enhanced purification can also be achieved by recrystallization of the precursor. Particularly, the precipitation of ammonium peroxofluorometalates, such as ammonium peroxofluoroniobate ((NH4)3Nb04F4), as a primary precursor, leads to significant reduction of the titanium contamination. Ammonium peroxofluoroniobate, (NH4)3Nb04F4, is... 

The precipitated precursor can be dissolved and re-crystallized from fluorine-free solutions. This provides excellent conditions for deep purification of the material and reduction of problematic impurities such as titanium, fluorine, etc. Peroxometalates decompose at relatively low temperatures forming tantalum or niobium oxides containing small amount of absorbed water. The absorbed water separation is achieved by further thermal treatment - drying and calcination - of the product ... 

MP borohydride catches one equivalent of the titanium catalyst, while the polystyrene-bound diethanolamine resin (PS-DEAM) can scavenge the remaining titanium catalyst. The borohydride reagent also assists in the reductive animation reaction. Final purification of the crude amine product is achieved with a polystyrene-bound toluene sulfonic acid resin scavenger that holds the amine through an ion exchange reaction, while impurities are washed off. The pure amine can be recovered with methanol containing 2M ammonium hydroxide. 

Pure titanium is obtained commercially from rutile (Ti02) by an indirect route in which Ti02 reacts with Cl2 gas and coke to yield liquid TiCl4 (bp 136°C), which is purified by fractional distillation. Subsequent reduction to Ti metal is then carried out by reaction with molten magnesium at 900°C, and further purification is effected by melting the titanium in an electric arc under an atmosphere of argon. 

Titanium is relatively abundant in the earth s crust (0.6%). The main ores are ilmenite (FeTi03) and rutile, one of the several crystalline varieties of Ti02. It is not possible to obtain the metal by the common method of reduction with carbon because a very stable carbide is produced moreover, the metal is rather reactive toward oxygen and nitrogen at elevated temperatures. Because the metal has uniquely useful properties, however, expensive methods for its purification are justified. In addition to a proprietary electrolytic method, there is the older Kroll... 

The synthesis of these nonatetraenoates Schemes 1.8 and 1.9) [21] utilizes low-valent titanium reductive elimination, a methodology which was also used in the stereospecific synthesis of ali-trans retinoic acid [21]. Because of the high stereospecificity, purification of intermediates prior to the final step was not necessary. 

A method for producing submicrometer (0.1 im), low-oxygen-content nonagglomerated TiC powders involved the carbothermal reduction of carbon-coated titanium diboride (TiOa) (27), where carbothermal synthesis proceeded via the purification of titanium oxycarbide toward pure titanium carbide. The carbon coating process provided a high contact area of the reactants to produce a TiC powder with uniform shape by synthesis at 1550 C for 4 h. 

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