Cobalt metals

The cobalt catalyst can be introduced into the reactor in any convenient form, such as the hydrocarbon-soluble cobalt naphthenate [61789-51 -3] as it is converted in the reaction to dicobalt octacarbonyl [15226-74-17, Co2(CO)g, the precursor to cobalt hydrocarbonyl [16842-03-8] HCo(CO)4, the active catalyst species. Some of the methods used to recover cobalt values for reuse are (11) conversion to an inorganic salt soluble ia water conversion to an organic salt soluble ia water or an organic solvent treatment with aqueous acid or alkah to recover part or all of the HCo(CO)4 ia the aqueous phase and conversion to metallic cobalt by thermal or chemical means. 

The binder metal, cobalt or nickel, is obtained as very fine powder and is blended with the carbide powders in ball mills, vibratory mills, or attritors... 

The scale formed on unalloyed cobalt during exposure to air or oxygen at high temperature is double-layered. In the range of 300 to 900°C, the scale consists of a thin layer of the mixed cobalt oxide [1308-06-17, Co O, on the outside and a cobalt(Il) oxide [1307-96-6] CoO, layer next to the metal. Cobalt(Ill) oxide [1308-04-9] maybe formed at temperatures below 300°C. Above 900°C, Co O decomposes and both layers, although of... 

Pure metallic cobalt has a soHd-state transition from cph (lower temperatures) to fee (higher temperatures) at approximately 417°C. However, when certain elements such as Ni, Mn, or Ti are added, the fee phase is stabilized. On the other hand, adding Cr, Mo, Si, or W stabilizes the cph phase. Upon fcc-phase stabilization, the energy of crystallographic stacking faults, ie, single-unit cph inclusions that impede mechanical sHp within the fee matrix, is high. 

Metallic cobalt, metallic nickel and an alloy powder containing 66-67% nickel, 13-16% chromium and 7% iron... 

The same sort of competition for electrons is involved in reaction (11), in which Zn(s) releases electrons and Cu+2 accepts them. This time the competition for electrons is such that equilibrium favors Zn+2 and Cu(s). By way of contrast, compare the reaction of metallic cobalt placed in a nickel sulfate solution. A reaction occurs,... 

Some data are also available (5) on the use of metallic cobalt and nickel supported on charcoal for high polymerization of ethylene. However, the application and investigation of these catalysts were not subsequently developed. 

Reduction of the 00 04 Catalysts. For all three samples the reduction of the surface of the 00 04 particles to metallic cobalt was observed by XPS following reaction in one atmosphere of flowing H2. After one hour at 350"C bulk C03O4 was completely reduced, while for CO304/Si02 2 the reduction was only about 80% complete. The COj04/Si02-923 sample was about 60% reduced at... 

C and both Si02 supported catalysts were completely reduced after cui hour at 500 C. These results indicate that the smaller particles were harder to reduce to metallic cobalt. 

Separation of two metals from a leach solution - as examples, mention may be made of solutions containing cobalt and copper, and nickel and copper. The former solution is treated by metallic cobalt to precipitate copper, and the latter by metallic nickel to precipitate copper. In both cases, the metal added to cement the copper is recovered afterwards. 

Metallic cobalt exhibits this phenomenon, and so do layered silicates and layered halides like Cdl2 or Bil3. In X-ray diffraction, stacking faults cause the appearance of diffuse streaks (continuous lines in the diffraction pattern). 

Chlorine Non-metals Cobalt trifluoride Silicon Fluorine Non-metals Iodine pentafluoride Metals, etc. 

Batley and Matousek [390,778] examined the electrodeposition of the irreversibly reduced metals cobalt, nickel, and chromium on graphite tubes for measurement by electrothermal atomisation. This method offered considerable potential for contamination-free preconcentration of heavy metals from seawater. Although only labile metal species will electrodeposit, it is likely that this fraction of the total metal could yet prove to be the most biologically important at the natural pH [779]. 

Among the earliest studies was that of Moffat (105). Poly-2-vinylpyri-dine, cross-linked with 4-8% divinylbenzene, was used as the coordinating support. The amount of cross-linking was found to be critical too little gave a soluble polymer, while too much gave an intractable material which absorbed little metal. Cobalt was used as the catalyst, and the reaction was conducted at 150°-200°C and 2000-3000 psi of 1/1 H2/CO. 

Several groups have reported deactivation of silica-supported cobalt catalysts. Holmen and coworkers19 30 have reported increased deactivation due to added (external) water in the feed to silica-supported Co catalysts. Kogelbauer et al 1 reported the formation of silicates. Catalysts recovered from FTS as well as catalysts deactivated by steam-treatment both showed fractions of non-reducible cobalt in TPR. The presence of metallic cobalt was a prerequisite for the silicate formation. 

Catalysts were prepared by incipient wetness impregnation of commercial supports using cobalt nitrate as a precursor. Metallic cobalt species were active centers in the ethanol steam reforming. Over 90% EtOH conversion achieved. Nature of support influences the type of byproduct formation. Ethylene, methane and CO are formed over Co supported on A1203, Si02 and MgO, respectively... 

C03O4, various Co species, and CoA O. The C00O/. particles were more readily reduced to metallic cobalt in H2 than the Co species were. After H2 reduction at 480°C, the CO hydrogenation activity in 10 atmospheres of 3H2 1C0 at 260°C for supported 5 wt % cobalt decreased as Co/Si02 > Co/Ti02 > C0/AI2O3 >... 

C0/K-AI2O3 compared to C0/AI2O3, the XPS experiments indicated that the amount of surface metallic cobalt present in the two systems was similar. 

Reduction to metallic cobalt in H2 occurred between 300-425°C for the Co30 particles, between 425-700°C for some Co+ species, and above 850°C for C0AI2O4. 

Due to the easier recycling of heterogeneous catalysts, Chung et al. developed an easy system that is based on the immobilization of 12 wt % metallic cobalt on commercially available charcoal [35]. The resulting yields were obtained in the range of 61-98%. After simple filtration the catalyst was reused up to ten times without significant loss of activity. 

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