Cobalt oxide preparation

Oxygen passed 0.5 hr. at 80° through benzylamine in dry benzene containing active cobalt oxide prepared from cobalt(II) sulfate with NaOH and O3-O2... 

Primary aliphatic amines may be oxidized to nitriles [151]. A new catalyst of this reaction is cobalt oxide prepared from cobalt (II) sulphate and sodium hydroxide [155]. Benzylamine dissolved in boiling benzene containing the catalyst is converted to benzonitrile in 85% yield when oxygen is bubbled through the solution. Arylsulphonyl cyanides may be prepared [156] in good yields by oxidation of the thiocyanates with 3-chloroperbenzoic acid in hexane at 60°. An aliphatic thiocyanate gave a low yield of the sulphonyl cyanide. 

Deep oxidation of propane was also obtained using ordered cobalt oxides prepared by a nanocasting route [31]. However, the role of the ordered structure in the catalytic performance does not seem to be beneficial. The enhanced catalytic activity, almost similar to that of the catalysts prepared by combustion of organic acids [42], has been explained in terms of both the high and low surface areas. The presence of oxygen vacancies, directly related to the high reducibihty of the ordered cobalt oxide species, was also very important. 

J.F., Murillo, R., Mastral, A.M., Aranda, A., Vazquez, I., Dejoz, A., and Solsona, B. (2010) Deep oxidation of volatile organic compounds using ordered cobalt oxides prepared by a nanocasting route, Appl. Catal. A Gen., 386 (1-2), 16-27. 

Among the other oxides that might be mentioned are manganese t hydroxide studied by van Bemmelen, cobalt oxide prepared by Muller, bismuth, lead, ceri-copper oxide, etc., and the many oxides of the platinum group studied by L. Wohler and Ruff.If... 

Garcia, T., Agouram, S., Sdnchez-Royo, J., et al. (2010). Deep Oxidation of Volatile Organic Compounds Using Ordered Cobalt Oxides Prepared by a Nanocasting Route, Appl. Catal. A Gen., 386, pp. 16-27. 

Han CH, Hong YS, Park CM, Kim K (2001) Synthesis and electrochemical properties of lithium cobalt oxides prepared by molten-salt synthesis using the eutectic mixture of LiCl-Li2C03. J Power Some 92 95—101... 

Calciothermic reduction of samarium oxide, in the presence of cobalt powder, yields samarium-cobalt alloys in the powder form. The process is popularly known as reduction diffusion. Samarium oxide, mixed with cobalt powder and calcium hydride powder or calcium particles, is heated at 1200 °C under 1 atm hydrogen pressure to produce the alloys. Cobalt oxide sometimes partly replaces the cobalt metal in the charge for alloy preparation. This presents no difficulty because calcium can easily reduce cobalt oxide. A pelletized mixture of oxides of samarium and cobalt, cobalt and calcium, with the components taken in stoichiometric quantities, is heated at 1100-1200 °C in vacuum for 2 to 3 h. This process is called coreduction. In reduction diffusion as well as in coreduction, the metals samarium and/or cobalt form by reduction rather quickly but they need time to form the alloy by diffusion, which warrants holding the charge at the reaction temperature for 4 to 5 h. The yield of alloy in these processes ranges from 97 to 99%. Reduction diffusion is the method by which most of the 500 to 600 t of the magnetic samarium-cobalt alloy (SmCOs) are produced every year. 

In contrast with the Schiff base salen, salicylaldehyde oxime (79) (salox) complexes of Co have received comparatively little attention, but a series of bis-bidentate divalent complexes of the form iraiis-Co(sa 1 ox)2( D M SO)2 have been reported.343 The heterocyclic bidentate oxime violurate (lH,3H-pyrimidine-2,4,5,6-tetrone 5-oximate, Hvi) (80) and its /V-methyl (mvi) and /V,/V -dimethyl (dmvi) derivatives form high-spin divalent [Co(vi)]+ and Co(vi)2 complexes, whereas [Co(vi)3] is low spin.344 The mixed-ligand Co(dmvi)2(phen) complex is also low spin. The crystal structure of m-Co(pxo)2Br2 (pxo = 2-acetylpyridine-l-oxide oxime) is isostructural with the Ni11 relative.345 The dichloro complex also adopts a cis configuration. The tridentate dioximes 2,6-diformyl-4-methylphenol dioxime and 2,6-diacetyl-4-methylphenol dioxime (Hdampo) form binuclear complexes of the type (81a) and (81b) respectively.346 Cobalt oxide nanoparticles were prepared by... 

Some cobalt oxides or possibly hydroxides were also observed however, it is highly likely that the majority of the oxide accumulation occurred on sample preparation. 

The more active cobalt catalyst for pyrolytic reactions was prepared by microwave calcination of cobalt nitrate which was converted to cobalt oxide by rapid microwave heating [7]. 

Sugimoto T. and Matuevic E. 1979. Colloidal cobalt hydrous oxides. Preparation and properties of monodispersed Co304. J. Inorg. Nucl. Chem. 41 165-72. 

Sarellas A., Niakolas D., Bourikas K., Vakros J., and Kordulis C. 2006. The influence of the preparation method and the Co loading on the structure and activity of cobalt oxide/y-alumina catalysts for NO reduction by propene. J. Colloid. Interf. Sci. 295 165-72. 

Ataloglou T., Vakros J., Bourikas K., Fountzoula C., Kordulis C., and Lycourghiotis A. 2005. Influence of the preparation method on the structure-activity of cobalt oxide catalysts supported on alumina for complete benzene oxidation. Appl. Catal. B Environ. 57 299-312. 

Christokova St. G., Stoyanova M., and Georgieva M. 2001. Low-temperature iron-modified cobalt oxide system. Part 1. Preparation and characterisation. Appl. Catal. A Gen. 208 235 2. 

Cobalt(II) chloride was dissolved in poly(amide acid)/ N,N-dimethylacetamide solutions. Solvent cast films were prepared and subsequently dried and cured in static air, forced air or inert gas ovens with controlled humidity. The resulting structures contain a near surface gradient of cobalt oxide and also residual cobalt(II) chloride dispersed throughout the bul)c of the film. Two properties of these films, surface resistivity and bullc thermal stability, are substantially reduced compared with the nonmodified condensation polyimide films. In an attempt to recover the high thermal stability characteristic of polyimide films but retain the decreased surface resistivity solvent extraction of the thermally imidized films has been pursued. 

Cobalt(ll) oxide is used as a pigment for ceramics and paints for drying paints, varnishes and oils for coloring glass as a catalyst and for preparation of other cobalt salts. The commercial product is a mixture of cobalt oxides. 

Tricobalt tetroxide is a minor component of commercial cobalt oxides. It is used in ceramics, pigments, and enamels. Other applications are in grinding wheels, in semiconductors, and for preparing cobalt metal. 

Cobaltous bromide and cobaltous iodide in the solid state absorb ammonia with formation of hexammino-cobaltous bromide, [Co(NH3)6]Br2, and hexammino - cobaltous iodide, [Co(NH3)6]I2, respectively. The compounds are unstable, and rapidly lose ammonia on heating and decompose on solution in water. Tetrammino-cobaltous iodide, [Co(NH3)4]I2, is also known. It may be prepared by treating a concentrated solution of cobaltous iodide with ammonia a pale red precipitate is formed, which gradually dissolves on warming, giving a violet-coloured liquid from which small rose-red crystals of the tetram-mine separate. It also is unstable, and decomposes on heating or on standing in air with loss of ammonia and formation of cobalt oxide. In aqueous solution it turns brown, ammonia is evolved, and a precipitate of cobaltous oxyiodide separates. 

Figure 1 shows Fourier transforms of EXAFS spectra of a few samples prepared. The radial distribution functions of these samples are different from that of nickel oxide or cobalt oxide [7]. All the Fourier transforms showed two peaks at similar distances (phase uncorrected) the peak between 1 and 2 A is ascribed to the M-0 bond (M divalent cation) and the peak between 2 and 3 A is ascribed to the M-O-M and M-O-Si bonds. The similar radial distribution functions in Figure 1 indicate that the local structures of X-ray absorbing atoms (Ni, Co, and Zn) are similar. No other bonds derived from metal oxides (nickel, cobalt and zinc oxides) were observed in the EXAFS Fourier transforms of the samples calcined at 873 K, which suggests that the divalent cations are incorporated in the octahedral lattice. 

Coball(lI) hydroxide exists in two allolropic forms, a blue or-Co (OH) and a pink /l-Co(OH) . The hydroxide is prepared by precipitation from u cobaltous salt solution by an alkali hydroxide. When the alkali is in excess the pink ft form is produced—the blue a-furni is produced when the cobalt salt is in excess. The salt slowly oxidizes in air at mom temperature and changes to hydrated cobaltic oxide, Co-Oi - H 0. The hydroxide is practically insoluble in H 0 and in bases, but highly soluble in mineral and organic acids. The commercial salt is used as Ihe starting material in the preparation of drying agents. 

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