Nickel oxidations with

Nickel chloride hexahydrate [7791-20-0] is formed by the reaction of nickel powder or nickel oxide with a hot mixture of water and HCl. Nickel duoride [13940-83-5], 4H2O, is prepared by the reaction of hydroduoric acid on nickel carbonate. Nickel bromide [18721 -96-5], NiBr2 6H20, is made... 

Nickel Sulfamate. Nickel sulfamate [13770-89-3] Ni(S02NH2)2 4H2O, commonly is used as an electrolyte ia nickel electroforming systems, where low stress deposits are required. As a crystalline entity for commercial purposes, nickel sulfamate never is isolated from its reaction mixture. It is prepared by the reaction of fine nickel powder or black nickel oxide with sulfamic acid ia hot water solution. Care must be exercised ia its preparation, and the reaction should be completed rapidly because sulfamic acid hydrolyzes readily to form sulfuric acid (57). 

Barrett and his colleagues , and Kosakhave summarised existing information on the scales formed on nickel-chromium alloys. Up to about 10% Cr, the thick black scale is composed of a double layer, the outer layer being nickel oxide and the inner porous layer a mixture of nickel oxide with small amounts of the spinel NiO CrjOj. Internal oxidation causes the formation of a subscale consisting of chromium oxide particles embedded in the nickel-rich matrix. At 10-20% Cr the scale is thinner and grey coloured and consists of chromium oxide and spinel with the possible presence of some nickel oxide. At about 25-30% Cr a predominantly chromium oxide scale is... 

Zhong Z, Yitzhak M, Yuri K, Yanming Z, Aharon G (1999) Sonochemical coating of nanosized nickel on alumina submicrospheres and interaction between the nickel and nickel oxide with substrate. Chem Mater 11 2350-2359... 

The first metal carbonyl prepared was Ni(CO)4, which was obtained by Mond in 1890. This extremely toxic compound was prepared by first reducing nickel oxide with hydrogen,... 

Several nickel salts are obtained by reactions of nickel oxide with mineral acids. Thus, the reaction of black nickel oxide with hot dilute sulfuric acid forms nickel sulfate, NiS04 6H2O. Similarly, dilute nitric acid, hydrochloric, and hydrobromic acids when heated react with the black form of nickel oxide to yield corresponding nickel salts as hexahydrates. 

Heating nickel oxide with hydrogen, carbon, or carbon monoxide reduces it to metallic nickel. 

The half-life of nickel in the lungs of rats exposed by inhalation has been reported to be 32 hours for nickel sulfate (mass median aerodynamic diameter [MMAD] 0.6 pm) (Hirano et al. 1994b), 4.6 days for nickel subsulfide ( Ni3S2 activity, median aerodynamic diameter [AMAD] 1.3 pm), and 120 days for green nickel oxide ( NiO, AMAD 1.3 pm) (Benson et al. 1994). Elimination half-times from the lung of rats of 7.7, 11.5, and 21 months were calculated for green nickel oxide with MMADs of 0.6, 1.2, and 4.0 pm, respectively (Tanaka et al. 1985, 1988). 

Ermakova and co-workers manipulated the Ni particle size to achieve large CF yields from methane decomposition. The Ni-based catalysts employed for the process were synthesized by impregnation of nickel oxide with a solution of the precursor of a textural promoter (silica, alumina, titanium dioxide, zirconium oxide and magnesia). The optimum particle size (10 0 nm) was obtained by varying the calcination temperature of NiO. The 90% Ni-10% silica catalyst was found to be the most effective catalyst with a total CF yield of 375 gcp/gcat- XRD studies by the same group on high loaded Ni-silica... 

Gray. Nickel oxide with titanium oxide... 

The difference to the copper process is, that the reduction of nickel oxide with methane is an endothermic process, thus a heat engine could be employed. Figures 9 and 10 show the enthalpy, entropy diagrams of the reactions outlined in equations (8) and (9). (A metallurgist will not favor the reoxidation of nickel since it is very difficult, but equilibrium thernodynamic considerations do allow it.)... 

Various active nickel catalysts obtained not via reduction of nickel oxide with hydrogen have been described in the literature. Among these are the catalysts obtained by the decomposition of nickel carbonyl 10 by thermal decomposition of nickel formate or oxalate 11 by treating Ni-Si alloy or, more commonly, Ni-Al alloy with caustic alkali (or with heated water or steam) (Raney Ni) 12 by reducing nickel salts with a more electropositive metal,13 particularly by zinc dust followed by activation with an alkali or acid (Urushibara Ni) 14-16 and by reducing nickel salts with sodium boro-hydride (Ni boride catalyst)17-19 or other reducing agents.20-24... 

Fig. 6.— Nickel oxide with Li on normal cation site and compensatory NF+ ion of higher charge.

We tried to dissolve away the free nickel oxide with a dilute mineral acid and found that treatment with 2 N hydrochloric acid for 24 hours at room temperature was enough to dissolve away the free nickel oxide in the catalyst selectively, as shown in Fig. 3 (6). 

Recently, two kinds of acid sites were proved to exist in nickel oxide-aluminosilicate prepared by a method practically identical with the SHOP method. One was the familiar type known to exist in aluminosilicates in general and the other originated from the combination of nickel oxide with silica and promoted the same reactions described above 14). 

Electrorefining Nickel Metal Anodes In the refining of nickel metal anodes, the principal reaction at the anode is the dissolution of nickel metal as nickel ions. The principal cathodic reaction is the reduction of nickel ions from solution. Nickel anodes are made by reducing nickel oxide with coke at temperatures up to 1550 °C and casting in molds. The practice is designed to obtain anodes with the desired strength and crystal size. 

INCO produced electrolytic nickel at its refinery in Port Colborne, Ontario, Canada. The production started in 1926. The anodes were made by reducing nickel oxide with coke, and the anodes contained about 93.5% Ni, 4% Cu, and 1% Co. The sulfur content was low, about 0.6%. The approximate composition of the purified electrolyte was 60 g L-1 Ni2+, 95 g L-1 S042-, 35 g L-1 Na+, 55 g L-1 Cl , and 16 g L 1 boric acid, and the temperature was 60 °C. The current density of the process was 16 A/sq.ft (approximately 170 A m-2) and the cell voltage was about 1.6 V. At the normal cell operating voltage, the principal impurities - iron, cobalt, lead, arsenic, and copper - dissolved into the solution with nickel. Silver, gold, the PGMs, sulfur, selenium, and tellurium fell to the bottom of the cell as an insoluble slime. The produced cathodes... 

Equations (73) and (74) take place at the cathode and anode, respectively. In practice, these reactions are more complex with the formation of different NiO(OH) modifications and a series of higher nickel oxides with different degrees of hydration. The overall reaction is summarized by... 

Derivation By adding ammonium hydroxide to a nitric acid solution of nickel oxide with subsequent crystallization. 

Ramachandran and Smith obtained satisfactory agreement with experimental results on the reduction of nickel oxide with carbon monoxide (pore opening case) by considering the product layer diffusion coefficient as an adjustable parameter. Similarly, the model predicted pore closure and reaction die-off for the reaction of calcium oxide with sulfur dioxide, where the molar volume of calcium sulfate product is about three times that of the calcium oxide reactant. 

There is evidence outside of catalytic studies that prior irradiation modifies the kinetics of reduction of metal oxides in hydrogen. Thus (181) the bombardment of nickel oxide with protons lowered the induction period and increased the rate of subsequent reduction. The induction period was lowered by a factor of about 3 at 250° after bombardment to ca. 10 1 ev/gm (IQi protons/cm, 260 mev). At higher temperatures of reduction the dilference became less until above 400° it was no longer detectable. Irradiation of nickel oxide with y-rays, on the other hand, decreased the rate of subsequent reduction in Hg and increased the induction period (181a, 181b). The effect set in at about 3 X 1021 ev/gm. 

The interactions of nickel and nickel oxide with adsorbed... 

Carbon monoxide has a high affinity for transition metals, forming the metal carbonyls (see 14.6.2.). Despite this, CO reacts slowly or not at all with metals. Some finely divided metals (Fe, Co) are converted slowly to the corresponding carbonyls under drastic conditions of T and P. Active Ni, as it is obtained by reducing nickel oxide with dihydrogen at 400°C, is, on the other hand, easily carbonylated to Ni(CO)4 even at temperatures as low as 30°C ... 

Spectra 7a, b correspond to samples which, in the hydrated state, contained hydrated and presumably isolated ions, whereas spectrum 7c corresponds to the case where wet sample contained some nickel hydroxyde. In these dealuminated zeolites, a high nickel loading exceeding the exchange capacity may be achieved by treatment with a hot solution, but upon heating, the nickel ions form a new phase which has the characteristics of a disperse nickel oxide with many coordinatively unsaturated nickel ions at the surface. 

Mond process for nickel refining reduction of nickel oxide with hydrogen, reaction with carbon monoxide to yield nickel carbonyl, and thermal decomposition to deposit pure nickel... 

Due to the kinetically inert nature of nickel oxide with respect to its dissolution in aqueous media the solubility of NiO has been studied only at elevated temperatures so far [80TRE/LEB2], [89ZIE/JON]. These studies are not suitable for the calculation of any thermodynamic properties of NiO because of the high uncertainty of the measured solubilities compared to the high-temperature emf data and the low-temperature heat capac-... 

Low-temperature heat capacities were determined for NiS (millerite) and Ni3S2 (heazlewoodite) between 50 and 298.15 K. The solid compounds were obtained by reaction of certain amounts of nickel oxide with sulphur. All products were characterised by X-ray diffraction analysis. Standard entropy values at 298.15 K were derived by integration of the respective heat capacity functions. In the case of millerite, the standard entropy is equal to 5° (NiS, (3, 298.15 K) = (52.97 + 0.33) J-K mor and the heat capacity at 298.15 K is C ,(NiS, p, 298.15 K) = 47.11 J K -mor , which agrees well with the result published by Gronvold and Stolen [95GRO/STO], C° (NiS, P,... 

It may be objected that a large extrapolation is involved in comparing the structure of supported nickel oxide with that of the reduced active catalyst. Some observations have been made which show that reduc-... 

Nickel is often associated with the PMs in nature, a good example being the ore body at Sudbury, Ontario, so one must be very careful to obtain a supply of nickel that contains a very low and known content of PMs. The usual chemicals used are nickel powder, nickel carbonate, or nickel oxide with flowers of sulfur, but for the determination of very low PM contents carbonyl nickel (prepared by thermal decomposition of Ni(CO)4) or ceramic grade NiO are preferred. 

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