Phases nickel-copper

The predominant process for manufacture of aniline is the catalytic reduction of nitroben2ene [98-95-3] ixh. hydrogen. The reduction is carried out in the vapor phase (50—55) or Hquid phase (56—60). A fixed-bed reactor is commonly used for the vapor-phase process and the reactor is operated under pressure. A number of catalysts have been cited and include copper, copper on siHca, copper oxide, sulfides of nickel, molybdenum, tungsten, and palladium—vanadium on alumina or Htbium—aluminum spinels. Catalysts cited for the Hquid-phase processes include nickel, copper or cobalt supported on a suitable inert carrier, and palladium or platinum or their mixtures supported on carbon. 

Copper—Nickels. The copper—nickel alloy system is essentially single phase across its entire range. Alloys made from this system are easily fabricated by casting, forming, and welding. They are noted for excellent tarnishing and corrosion resistance. Commercial copper alloys extend from 5 to 40 wt % nickel. Monel is a nickel—copper alloy that is outside of this range and contains 29—53 wt % of copper. 

Phase diagrams have been measured for almost any alloy system you are likely to meet copper-nickel, copper-zinc, gold-platinum, or even water-antifreeze. Some... 

In the initial investigations the samples of nickel or nickel-copper alloys were used in the form of foils transformed into their respective hydride phases by saturating them electrolytically with hydrogen (7). The presence of a hydride phase was confirmed by X-ray diffraction (8). The catalytic... 

Coefficients of H Atom Recombination, y, at —78°C on Nickel or Nickel-Copper Foils and Their Respective 0-Hydride Phases... 

In these particular experiments it proved impossible to investigate the effect of copper concentration on the catalytic activity of alloys free of the hydride phase. Figure 10 69, 64a, 65) illustrates the changing values of the recombination coefficient on nickel-copper alloys related to the composition of the alloy at room temperature. The small amount of copper introduced into the nickel already distinctly decreased the catalytic ac-... 

This conclusion was additionally confirmed by Palczewska and Janko (67) in separate experiments, where under the same conditions nickel-copper alloy films rich in nickel (and nickel films as well) were transformed into their respective hydride phases, which were proved by X-ray diffraction. The additional argument in favor of the transformation of the metal film into hydride in the side-arm of the Smith-Linnett apparatus consists of the observed increase of the roughness factor ( 70%) of the film and the decrease of its crystallite size ( 30%) after coming back from low to high temperatures for desorbing hydrogen. The effect is quite similar to that observed by Scholten and Konvalinka (9) for their palladium catalyst samples undergoing the (a — j8) -phase transformation. 

In the particular case of nickel-copper alloys their hydrogen pretreatment may result in phase segregation (48), at least at the surface. The desegregated rich in nickel alloy can display its relatively high catalytic quality and even keep it down to a certain temperature (lower than in the case of nickel itself), which would be the critical temperature of a given Ni-Cu-H system. 

Gee and Bruland [953] used 61Ni, 65Cu, and 68Zn in waters collected in San Francisco Bay to trace the kinetics of nickel, copper, and zinc exchange between dissolved and particulate phases. The technique involved an organic ligand sequential extraction followed by analysis with high-resolution ICP-MS. 

An improved procedure for the laboratory preparation of 2,5-dimethylpyrazine has been reported.166 a-Amino alcohols are convenient precursors for the industrial preparation of alkylpyrazines. Thus when they are heated in the vapor phase with copper chromite catalysts, they are converted mainly into pyrazines [Eq. (8)] with hydrogenation catalysts such as Raney nickel, piperazines are the... 

Alloys are prepared commercially and in the laboratory by melting the active metal and aluminum in a crucible and quenching the resultant melt which is then crushed and screened to the particle size range required for a particular application. The alloy composition is very important as different phases leach quite differently leading to markedly different porosities and crystallite sizes of the active metal. Mondolfo [14] provides an excellent compilation of the binary and ternary phase diagrams for aluminum alloys including those used for the preparation of skeletal metal catalysts. Alloys of a number of compositions are available commercially for activation in the laboratory or plant. They include alloys of aluminum with nickel, copper, cobalt, chromium-nickel, molybdenum-nickel, cobalt-nickel, and iron-nickel. 

Corrosion by dealloying is common in brasses here the zinc component of the alloy is preferentially removed. Brasses with high proportions of the P phase are especially prone to this type of attack. The mechanism appears to be corrosion of both copper and zinc from the metal the zinc passes into solution but the copper is re-deposited with a porous structure of low strength. Aluminium bronzes also suffer dealloying of the aluminium component if incorrectly heat treated. Other metals which may be preferentially dissolved from their alloys are manganese from copper-manganese, nickel from copper-nickel, copper from either copper-silver or copper-gold, and tin from tin-lead (solders). It is evident from this list that it is the component which is anodic to the alloy which is removed. 

Stone W. E. and Fleet M. E. (1991) Nickel-copper sulfides from the 1959 eruption of Kilauea volcano, Hawaii contrasting compositions and phase relations in eruption pumice and Kilauea Iki lava lake. Am. Mineral 76, 1363-1372. 

If the alloy exists in two phases, that phase with the lower sublimation energy will form on the outer surface. If the nickel-copper system is equilibrated at temperatures near 200°C, it exists as two phases of constant composition in equilibrium. 35 The relative amounts of the phases depends on the overall... 

Copper-Nickel. - Copper-nickel alloys with macroscopic particles equilibrated above 600 K exist as a continuous series of solid solutions, whereas below this temperature a two-phase system with the Cu-rich phase enveloping a... 

Hydrogenation of unsaturated side chains of aromatic compounds can be achieved in the liquid phase with Raney nickel or platinum and in the gas phase with copper catalysts. In most cases the differing rates of hydrogenation of olefinic and aromatic double bonds permits selective saturation of the side chain. 

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