Preparation of activated nickel

Raney nickel has long been known as a hydrogenation catalyst. Other forms of active nickel can be easily prepared by reducing nickel salts in situ with NaBH4, Fe, Grignard reagents, etc. (199-202). 

Allison et al. prepared the catalyst by decomposing nickel formate in a paraffin-paraffin oil mixture in a vacuum of a water-stream pump.45 The nickel catalyst thus prepared was not pyrophoric, not sensitive to air and chloride, and showed excellent catalytic properties in the hydrogenation of aqueous solutions of aromatic nitro compounds such as the sodium salts of m-nitrobenzenesulfonic acid, o-nitrobenzoic acid, and p-nitrophenol at pH 5-6. Sasa prepared an active nickel catalyst for the hydrogenation of phenol by decomposing nickel formate in boiling biphenyl [boiling point (bp) 252°C], diphenyl ether (bp 255°C), or a mixture of them (see eq. 11.12)42... 

L. M. S. Silva, J. J. M. Orfao and J. L. Figueiredo. Formation of two metal phases in the preparation of activated carbon-supported nickel catalysts. Applied Catalysis A General, 209, 145-154 (2001). 

Raney nickel catalysts (1, 723). The usual preparation of Raney nickel catalysts W-2 and W-h requires a tedious washing process with distilled water to remove the last traces of salt. Wynberg ct a P report that demineralization can be accomplished readily with an ion-exchange resin (Amberlite IR 121), hydrogen form). The resulting catalysts are somewhat more active than those prepared by the Organic Syntheses procedures. 

Another form of active nickel catalyst has been prepared by the reaction of lithium iso-propoxide with nickel chloride to give nickel iso-propoxide. Heating this salt to 100°C in iso-propanol gives a black, finely divided nickel catalyst that is active for the hydrogenation of a variety of functional groups. ... 

After decomposition of the aluminum alloys there is still residual aluminum in the metal, and this residue seems to be in part responsible for the activity of the catalyst. If this residue is largely removed by continued extraction, the catalyst becomes inactive.157 Alloys containing more than 75% of nickel are only partly attacked by aqueous sodium hydroxide, or are not attacked at all then decomposition has to be undertaken with very concentrated sodium hydroxide solution or by adding solid sodium hydroxide to the molten mass.158 Alloys containing between 30% and 50% of active metal are most suitable for preparation of active metal catalysts. 

Adsorption by carbon, which is one of the oldest adsorption methods used, has been reviewed and evaluated for the preconcentration of trace metals (794). Many authors have discussed the preparation of activated charcoal and carbon from a wide variety of usually local sources. The applications to water treatment are far too numerous to mention other than a few. Jo (795) carbonized a resin and a gum and hydrated the residue above 600 C to produce an adsorbant selective for cadmium(II). Kuzin et al, 196) used deashed active carbon and oxidized carbon for the quantitative sorption of copper, lead, zinc, and nickel from nearly neutral solutions containing 1-2 M alkali-metal halide. Pearson and Siviour (797) converted the metal-ion species to amine complexes before adsorbing these onto carbonaceous materials such as brown charcoal char or cellulose. Mercury vapor can be removed from a solution by reduction followed by passage of a nitrogen stream and adsorption by activated charcoal (798). Activated carbon, which had been oxidized with nitric acid, has been used to extract several metals including divalent nickel, cadmium, cobalt, zinc, manganese, and mercury from fresh water, brine, and seawater (799, 200). 

Preparation of Rieke Nickel, Characterization of Active Nickel Powder, and Some Chemistry... 

Previous communications [111] have shown the high reactivity and utility of activated nickel powder prepared by the hthium metal reduction of nickel... 

By knowing the active intermediates in these polymerizations, Cheng and Deming were also able to use chiral donor ligands to prepare optically active nickel initiators for the enan-tioasymmetric polymerization of NCAs. Since polypeptides are chiral polymers, the ability to control stereochemistry during polymerization is a feature worth pursuing. This is especially true since the self-assembly and properties of polypeptides are critically dependent on the stereochemistry of the amino acid components. Due to constraints imposed by the initial... 

Ma.nufa.cture. Nickel carbonyl can be prepared by the direct combination of carbon monoxide and metallic nickel (77). The presence of sulfur, the surface area, and the surface activity of the nickel affect the formation of nickel carbonyl (78). The thermodynamics of formation and reaction are documented (79). Two commercial processes are used for large-scale production (80). An atmospheric method, whereby carbon monoxide is passed over nickel sulfide and freshly reduced nickel metal, is used in the United Kingdom to produce pure nickel carbonyl (81). The second method, used in Canada, involves high pressure CO in the formation of iron and nickel carbonyls the two are separated by distillation (81). Very high pressure CO is required for the formation of cobalt carbonyl and a method has been described where the mixed carbonyls are scmbbed with ammonia or an amine and the cobalt is extracted as the ammine carbonyl (82). A discontinued commercial process in the United States involved the reaction of carbon monoxide with nickel sulfate solution. 

Electrochemistry and Kinetics. The electrochemistry of the nickel—iron battery and the crystal stmctures of the active materials depends on the method of preparation of the material, degree of discharge, the age (Life cycle), concentration of electrolyte, and type and degree of additives, particularly the presence of lithium and cobalt. A simplified equation representing the charge—discharge cycle can be given as ... 

Salts of neodecanoic acid have been used in the preparation of supported catalysts, such as silver neodecanoate for the preparation of ethylene oxide catalysts (119), and the nickel soap in the preparation of a hydrogenation catalyst (120). Metal neodecanoates, such as magnesium, lead, calcium, and zinc, are used to improve the adherence of plasticized poly(vinyl butyral) sheet to safety glass in car windshields (121). Platinum complexes using neodecanoic acid have been studied for antitumor activity (122). Neodecanoic acid and its esters are used in cosmetics as emoUients, emulsifiers, and solubilizers (77,123,124). Zinc or copper salts of neoacids are used as preservatives for wood (125). 

Two different sets of experimental conditions have been used. Buu-Hoi et al. and Hansen have employed the method introduced by Papa et using Raney nickel alloy directly for the desulfurization in an alkaline medium. Under these conditions most functional groups are removed and this method is most convenient for the preparation of aliphatic acids. The other method uses Raney nickel catalysts of different reactivity in various solvents such as aqueous ammonia, alcohol, ether, or acetone. The solvent and activity of the catalyst can have an appreciable influence on yields and types of compounds formed, but have not yet been investigated in detail. In acetic anhydride, for instance, desulfurization of thiophenes does not occur and these reaction conditions have been employed for reductive acetylation of nitrothiophenes. Even under the mildest conditions, all double bonds are hydrogenated and all halogens removed. Nitro and oxime groups are reduced to amines. 

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