Nickel higher oxides, decompositions

Tervalent copper and nickel are involved in the autoxidation reactions of [Cu(H 3G4)] and [Ni(H 3G4)] respectively. In the case of nickel, decomposition of [Ni(H 3G4)] proceeds by decarboxylation of the terminal carboxy-group adjacent to the peptide nitrogen. - With copper, decomposition of [Cu-(H sG4)] proceeds through a carbon-centred free radical produced by abstraction of a hydrogen atom from the peptide backbone. Bulky carbon substituents assist the stabilization of the higher-oxidation state ions, and a study of the stabilities of leucyl tripeptide complexes with copper(ii) and nickel(u) has been reported. Copper(iii) and nickel(iii) tripeptide complexes of a-aminoisobutyric acid are thermally stable but are readily decomposed by photochemical pathways. Resonance Raman and other studies with copper(iii) peptide complexes have also been reported. ... 

For the higher molecular weight feedstocks such as liquefied petroleum gas (usually propane CjH8) and naphtha (q.v.), nickel catalysts with alkaline carriers or alkaline-free catalysts with magnesium oxide as additive can be used. Both types of catalyst are less active than the conventional nickel catalyst. Therefore, a less rapid decomposition of the hydrocarbons is achieved. At the same time, the reaction of water with any carbon formed is catalyzed. 

The temperature required for the reduction of cobalt oxides to the metal appears to be somewhat higher than for the reduction of nickel oxide. The catalyst with a higher catalytic activity is obtained by reduction of cobalt hydroxide (or basic carbonate) than by reduction of the cobalt oxide obtained by calcination of cobalt nitrate, as compared in the decomposition of formic acid.91 Winans obtained good results by using a technical cobalt oxide activated by freshly calcined powdered calcium oxide in the hydrogenation of aniline at 280°C and an initial hydrogen pressure of 10 MPa (Section... 

The decomposition of the lower sulfides of the heavy metals and the recovery of the metal as soluble salts and of sulfur in the elemental form have been demonstrated for pyrite, pyrrhotite, chalcopyrite, sphalerite, galena, molybdenite, and associated metals such as nickel and cobalt. Pyrite and chalcopyrite are higher sulfides and to be amenable to this treatment have to be thermally decomposed at 600-650 C prior to leaching. The reactions with nitric acid are exothermic, and are carried out below 1 atm and at around 100°C. In addition to the sulfides, this technique has been applied successfully to the extraction of nonferrous metals from partly oxidized sulfide ores, fayalite slags, copper scrap, and other intermediate products, such as residue from electrolytic zinc plats. 

Still debated. Whereas Krasil shchikov proposed (282) slow chemical decomposition of a higher nickel oxide,... 

Evacuation of the oxygen atmosphere down to 10- torr does not produce a desorption (24) and no thermal effect is registered (68). COa fads) is therefore a stable species at room temperature, in the presence of oxygen or under vacuum. Its spontaneous decomposition to yield carbon dioxide is not possible at room temperature but is observed at 200° (24). A subsequent adsorption of carbon monoxide is possible on the samples of NiO(200°) and NiO(250°) (Table V) and, in both cases, carbon dioxide is then found in the cold trap. This adsorption of carbon monoxide decreases the electrical conductivity of the samples which, however, remains higher than the conductivity of the initial nickel oxide [7 X 10-i< ohm-i cm-i for NiO(200°) 1.6 x lO- o ohm-i cm-i for NiO(250°)] (25, 41). It was concluded from these experiments that a fraction of C03 (ads) ions is decomposed at room temperature by carbon monoxide and that the interaction product is carbon dioxide, which is, at least partially, desorbed to the gas phase (0.5 cm /gm) (25). 

The advantages of using chloride electrolytes compared with sulfate electrolytes are higher electrical conductivity, lower electrolyte viscosity, lower overpotential for nickel reduction, and higher solubility and activity of nickel. An important factor is the lower anode potential of chlorine evolution compared with oxygen evolution in sulfate electrolytes using the common lead anodes. Chloride electrolytes require insoluble or dimensionally stable anodes, usually titanium coated with an electroactive noble metal or oxide, and a diaphragm system to collect the CI2 gas from the anode. The chlorine liberated at the anode is recycled for use in the leach circuits. In practice, some decomposition of water... 

The best catalyst was found to consist of zinc oxide and copper (or copper oxide) with an admixture of compounds of chromium. The success of the operation depended upon (a) the absence of alkali, which would cause decomposition of the methanol and the production of higher alcohols and oily products, and (b) the complete elimination of all metals except copper, aluminum and tin from those parts of the apparatus which come in contact with the reacting gases. Contact of carbon monoxide with iron, nickel, or cobalt had to be avoided since they formed volatile carbonyls winch deposited metal, by decomposition, on the active catalyst surface and thereby acted as poisons to destroy activity. 

---