Cobalt Metal Production

Metallic cobalt is, as mentioned above, produced as cobalt powder and cobalt cathode sheets. Mined ore is as a rule refined in the country of origin. Examples are  

The world refinery capacity was in 2000 estimated at 60000 tonnes cobalt per year [30.4] of which the DRChas 28%, Finland 16, Russia 13, Canada 8, Zambia 8, Norway 7, Australia 6 and China 3%. 

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Fig. 5. Flow sheet foi Sheiiitt-Goidon process for production of nickel and cobalt metals from sulfide ore.

The mauve colored cobalt(II) carbonate [7542-09-8] of commerce is a basic material of indeterminate stoichiometry, (CoCO ) ( (0 )2) H20, that contains 45—47% cobalt. It is prepared by adding a hot solution of cobalt salts to a hot sodium carbonate or sodium bicarbonate solution. Precipitation from cold solutions gives a light blue unstable product. Dissolution of cobalt metal in ammonium carbonate solution followed by thermal decomposition of the solution gives a relatively dense carbonate. Basic cobalt carbonate is virtually insoluble in water, but dissolves in acids and ammonia solutions. It is used in the preparation of pigments and as a starting material in the preparation of cobalt compounds. 

Hi) Cobalt formate. There is evidence that the kinetics of decomposition of cobalt formate [1026,1027] are similar to those of the nickel salt, considered in some detail below. A significant point of difference, however, is that metal production during reaction of the former is preceded by formation of cobalt oxides [1028]. 

On photolyzing CoziCOg in the matrix (20), a number of photoproducts could be observed. The results of these experiments are summarized in Scheme 4, which illustrates the various species formed. Of particular interest is the formation of Co2(CO)7 on irradiation of Co2(CO)g in CO (254 nm), as this species had not been characterized in the metal-atom study of Hanlan et al. (129). Passage of Co2(CO)g over an active, cobalt-metal surface before matrix isolation causes complete decomposition. On using a less active catalyst, the IR spectrum of Co(CO)4 could be observed. An absorption due to a second decomposition product, possibly Co2(CO)g, was also noted. 

The oxidation of cobalt metal to inactive cobalt oxide by product water has long been postulated to be a major cause of deactivation of supported cobalt FTS catalysts.6 10 Recent work has shown that the oxidation of cobalt metal to the inactive cobalt oxide phase can be prevented by the correct tailoring of the ratio Ph2cJPh2 and the cobalt crystallite size.11 Using a combination of model systems, industrial catalyst, and thermodynamic calculations, it was concluded that Co crystallites > 6 nm will not undergo any oxidation during realistic FTS, i.e., Pi[,()/I)i,2 = 1-1.5.11-14 Deactivation may also result from the formation of inactive cobalt support compounds (e.g., aluminate). Cobalt aluminate formation, which likely proceeds via the reaction of CoO with the support, is thermodynamically favorable but kinetically restricted under typical FTS conditions.6... 

Two aspects of porphyrin electrosynthesis will be discussed in this paper. The first is the use of controlled potential electroreduction to produce metal-carbon a-bonded porphyrins of rhodium and cobalt. This electrosynthetic method is more selective than conventional chemical synthetic methods for rhodium and cobalt metal-carbon complexes and, when coupled with cyclic voltammetry, can be used to determine the various reaction pathways involved in the synthesis. The electrosynthetic method can also lead to a simultaneous or stepwise formation of different products and several examples of this will be presented. 

Preparation. Industrially, cobalt is normally produced as a by-product from the production of copper, nickel and lead. The ore is roasted to form a mixture of metals and metal oxides. Treatment with sulphuric acid leaves metallic copper as a residue and dissolves out iron, cobalt and nickel as the sulphates. Iron is separated by precipitation with lime (CaO) while cobalt is produced as the hydroxide by precipitation with sodium hypochlorite. The trihydroxide Co(OH)3 is heated to form the oxide and then reduced with carbon (as charcoal) to form cobalt metal. 

Cobalt is the 32nd most abundant element on Earth even though it makes up only 0.003% of the Earth s crust. It is not found in the free metallic state, despite being widely distributed in igneous rocks as minerals. Its two most common mineral ores are cobaltite (CoAsS) and erythrite [Co lAsO l ]. These ores are placed in blast furnaces to produce cobalt arsenide (COjAs), which is then treated with sulfuric acid to remove the arsenic. Finally, the product cobalt tetraoxide (Co O ) is reduced by heat with carbon (Co O + C — 3Co + 2COf resulting in cobalt metal. 

The dust and powder of cobalt metal, ores, and some compounds, such as cobaltous nitrate [ColNOfljT bH O], are flammable and toxic if inhaled. Cobaltous acetate [ColCjHjOjlj dHjO], which is soluble in water, is not allowed to be used in food products because of its toxicity. 

Cobalt octacarbonyl reacts with polydiynes obtained by Co y-irradiation to give metallated products in which 50% of the available alkyne moieties are coordinated. Reactions with M(CO)2Cp 2 (M = Mo, W) also gave partly characterized polymeric metallated products, together with significant amounts of M(CO)3Cp 2. °... 

With the ligand dbp similar reactions yielded CoCl(dbp)3 and Co(dbp)4, but no Co(BH4)(dbp)3. Triphenyl-arsine and -stibine and CoCl2 were reduced to black products, probably cobalt metal. From NaBH3CN is afforded a Co(BH3CN)(Ph2-PCH2CH2PPh2) complex, but this does not subsequently yield a dinitrogen complex. 

The hydroformylation (or 0x0 ) reaction was discovered in 1938 by Roelen who was working on the formation of oxygenates as by-products of the Fischer-Tropsch reaction over cobalt catalysts. It soon became clear that the aldehydes and alcohols found were the products of secondary reactions undergone by the 1-alkenes (which are the primary products of the Fischer-Tropsch reaction, Section 4.7.2) with syngas. Further work showed that Roelen had discovered a new reaction, in which the elements of H and CHO were added to an olefin (hence hydroformylation), and which was catalyzed by cobalt. It was later found that the true precatalyst was not cobalt metal but derivatives of dicobalt octacarbonyl, such as the hydride, CoH(CO)4. 

Tailoring of the product distribution is possible by a limitation of chain growth by pore size. This has been demonstrated by Ballivel Tkatchenko and Tkatchenko using zeolite catalysts. Ruthenium, iron or cobalt metal particles in Y-zcolilc supcrcagcs were prepared by thermal decomposition of the carbonyls. These metal-zeolite catalysts give selective formation of )- hydrocarbons [471. 

Another heterogeneous 02-activation system uses supported cobalt metal to catalyze the gas-phase oxygenation of cyclohexane to cyclohexanol and cyclohexanone, which are intermediates for the production of adipic acid (H02C(CH2)4C02H) (equation 123). 

Although rare, manufacturing errors can cause production of products that contain toxic metals. In the early 1960s, a Canadian beer brewery accidentally contaminated a large lot of its product with cobalt The product was sold to and consumed by the public, resulting in an outbreak of renal disease and cardiomyopathy. In this type of situation, the U.S. Public Health Service is often called in to identify the cause of an outbreak of unusual symptoms. The clinical laboratory should be prepared to support these types of investigations. 

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