Metallic nickel, from hydrogenation

In normal battery operation several electrochemical reactions occur on the nickel hydroxide electrode. These are the redox reactions of the active material, oxygen evolution, and in the case of nickel-hydrogen and nickel-metal hydride batteries, hydrogen oxidation. In addition there are parasitic reactions such as the corrosion of nickel current collector materials and the oxidation of organic materials from separators. The initial reaction in the corrosion process is the conversion of Ni to Ni(OH)2. 

The hydrogen production from metallic nickel in such system occurred with low rate at pH below 5.0 and stopped after several minutes. At pH above 7.0 hydrogenase catalyzed the... 

On the other hand, some of Suhrmann s electrical resistance measurements on nickel and platinum films and Eischens observations, of the effect of Hj on the infrared spectrum of chemisorbed CO on platinum, referred to earlier, suggest electron-transfer from hydrogen to the metal, i.e., adsorption of positive ions. 

Throughout these studies, no product other than propane was observed. However, subsequent studies by Sinfelt et al. [249—251] using silica-supported Group VIII metals (Co, Ni, Cu, Ru, Os, Rh, Ir, Pd and Pt) have shown that, in addition to hydrogenation, hydrocracking to ethane and methane occurs with cobalt, nickel, ruthenium and osmium, but not with the other metals studied. From the metal surface areas determined by hydrogen and carbon monoxide chemisorption, the specific activities of... 

The influence of the reduction temperature was studied for nickel-zeolite catalysts. Molecular sieves of type A, X, and Y which contained about 7-8 wt % nickel were used. Figure 1 shows the results of the study on the formation of metal surface in reduction temperatures from 250 to 600° C. Reduction of nickel with hydrogen begins at 250-300° C for all... 

For maximum catalytic activity, the metal usually is prepared in a finely divided state. This is achieved for platinum and palladium by reducing the metal oxides with hydrogen prior to hydrogenation of the alkene. A specially active form of nickel ( Raney nickel ) is prepared from a nickel-aluminum alloy. Sodium hydroxide is added to the alloy to dissolve the aluminum. The nickel remains as a black powder which is pyrophoric (bums in air) if not kept moist ... 

Arrhenius parameters for nickel carbide hydrogenation 162) is close to both lines on Fig. 3. Compensation behavior for reactions on the carbide phase must include an additional feature in the postulated equilibria, to explain the removal of excess deposited carbon, if the active surface is not to be poisoned completely. The relative reduction in the effective active area of the catalyst accounts for the lower rates of reaction on nickel carbide, and the difference in the compensation line from that of the metal (Fig. 3) is identified as a consequence of the poisoning-regeneration process. After any change in reaction conditions, a period of reestablishment of surface equilibria was required before a new constant reaction rate was attained (22). 

Hydrogen peroxide is extracted with water from the reaction liquor the final product so obtained contains some 20 per cent of hydrogen peroxide. Extraction is carried out in a tower in which the water flows in a downward direction over trays while the solution of quinone passes countercurrently upwards. The small amount of water remaining in the quinone phase is removed in another tower by extraction with a concentrated solution of potassium carbonate (33 to 50 per cent) finally all traces of hydrogen peroxide are eliminated by allowing the liquor to pass over a porous material on the surface of which metallic nickel and silver were deposited following this the liquor is filtered and regenerated. 

Following the development of sponge-metal nickel catalysts by alkali leaching of Ni-Al alloys by Raney, other alloy systems were considered. These include iron [4], cobalt [5], copper [6], platinum [7], ruthenium [8], and palladium [9]. Small amounts of a third metal such as chromium [10], molybdenum [11], or zinc [12] have been added to the binary alloy to promote catalyst activity. The two most common skeletal metal catalysts currently in use are nickel and copper in unpromoted or promoted forms. Skeletal copper is less active and more selective than skeletal nickel in hydrogenation reactions. It also finds use in the selective hydrolysis of nitriles [13]. This chapter is therefore mainly concerned with the preparation, properties and applications of promoted and unpromoted skeletal nickel and skeletal copper catalysts which are produced by the selective leaching of aluminum from binary or ternary alloys. 

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