Reduced Cobalt

No determination was made as to whether differences between C0/AI2O3 and C0/K-AI2O3 were due to the presence of K, the higher support calcination temperature, or the lower surface area of K-AI2O3. It should be noted that although the total amount of bulk cobalt reducible in H2 at 480°C had increased in... 

The cobalt reduces the number of nickel ions in the lithium layer. 

Physical Condition of the Metal.—The more finely divided the metal the greater is its power of occluding hydrogen. This probably explains many of the apparently anomalous results detailed in the literature on the subject. Thus, for example, cobalt reduced from the bromide does not possess the property of occluding hydrogen to any important extent.6 The metal obtained, on the other hand, by reduction from its oxides contains varying amounts of the gas. Reduced at... 

The requisite amount of this solution is added hot to one containing the nickel and cobalt salts acidulated with acetic acid, and the whole allowed to stand overnight. On filtering, the precipitate is wrashed with 12 per cent, hydrochloric acid to remove any nickel carried down mechanically with the cobalt, and after washing with water and drying, the whole is incinerated with a little pure oxalic acid, and the cobalt reduced to the metallic condition in a current of hydrogen. Copper, chromium, and iron are also precipitated by the naphthol, and should not, therefore, be present in the original solution. 

In the figures 1 and 2 we have mentioned the results obtained on the Pt-Co catalysts and it is obvious that the light-off is 25°C lower on the catalyst where the two salts were reduced i) the cobalt reduced at first, ii) then reduction of platinum. 

To further test this hypothesis freshly-reduced catalysts were reacted with high-pressure steam (5 atm). A significant loss of BET surface area (from 215 to 188 mVg) is observed after Co/Davisil was reduced at 1 atm and reacted with 5 atm steam for 24 h (see Table 3). Increasing the space velocity by a factor of four also increases the rate of BET surface area loss (from 12.5 % / 24 h to 39.0 % / 24 h). Extents of reduction of cobalt oxide to cobalt metal before and after steam treatment are shown in Table 3. After steam treatment the cobalt oxide-support interaction is apparently substantially increased, i.e., the fraction of cobalt reduced to the metal at 400°C decreases from 89 to 4% moreover, the amount of cobalt-silicates (as inferred from TPR spectra shown elsewhere [22, 23]) also increases after steam treatment. This latter observation is consistent with the substantially higher extent of reduction of these catalysts (71-72%) at 750 C, a temperature at which a significant fraction of cobalt silicate can be reduced to the metal. 

It has been also reported that the catalytic behaviour of Co catalysts for steam reforming of ethanol is enhanced by promotion with Fe or Mn as a consequence of the effect of these metals on cobalt reducibility. The catalytic activity of Co catalysts supported on ZnO and promoted with Fe and Mn (1 %) was compared with that of Ni catalysts supported on LaaOs-AlgOs. The Co catalysts do not promote methane-forming reactions such as ethanol cracking and acetaldehyde decarbonylation, nor do they facilitate the reverse methane steam reforming reaction. The promotion effect of Mn on Co/ZnO catalysts in the steam reforming of ethanol has been studied in coprecipitated catalysts. Alloy particles in Co-Mn/ZnO catalysts prepared by... 

Electrochemical tests performed on simple cobalt oxides demonstrate specific capacities between 700 and 1100 mAh/g and an excellent cycle behavior. The formation of nanoparticles of cobalt dispersed in a Li20 matrix occurs because of the reduction of the cobalt in CoO. Li20 is often inactive in electrochemistry, but its formation in situ in the material means it is able to be electrochemically active. However, the cost of cobalt reduces the commercial prospects of this type of compound. 

CoAsS, are also used as sources. The ore is roasted and Co is precipitated as the hydroxide and then reduced to Co with carbon (hep below 417 - C, cep to m.p.). The metal is silvery white and readily polished. It dissolves in dilute acids and is slowly oxidized in air. Adsorbs hydrogen strongly. The main use of cobalt is in alloys. Cobalt compounds are used in paints and varnishes, catalysts. Cobalt is an essential element in the diet. World production 1976 32 000 tonnes metal. 

Aqueous ammonia can also behave as a weak base giving hydroxide ions in solution. However, addition of aqueous ammonia to a solution of a cation which normally forms an insoluble hydroxide may not always precipitate the latter, because (a) the ammonia may form a complex ammine with the cation and (b) because the concentration of hydroxide ions available in aqueous ammonia may be insufficient to exceed the solubility product of the cation hydroxide. Effects (a) and (b) may operate simultaneously. The hydroxyl ion concentration of aqueous ammonia can be further reduced by the addition of ammonium chloride hence this mixture can be used to precipitate the hydroxides of, for example, aluminium and chrom-ium(III) but not nickel(II) or cobalt(II). 

Here, effectively, the Co " (aq) is being oxidised by the nitrite ion and the latter (in excess) is simultaneously acting as a ligand to form the hexanitrocobaltate(III) anion. In presence of cyanide ion CN. cobalt(II) salts actually reduce water to hydrogen since... 

High purity acetaldehyde is desirable for oxidation. The aldehyde is diluted with solvent to moderate oxidation and to permit safer operation. In the hquid take-off process, acetaldehyde is maintained at 30—40 wt % and when a vapor product is taken, no more than 6 wt % aldehyde is in the reactor solvent. A considerable recycle stream is returned to the oxidation reactor to increase selectivity. Recycle air, chiefly nitrogen, is added to the air introducted to the reactor at 4000—4500 times the reactor volume per hour. The customary catalyst is a mixture of three parts copper acetate to one part cobalt acetate by weight. Either salt alone is less effective than the mixture. Copper acetate may be as high as 2 wt % in the reaction solvent, but cobalt acetate ought not rise above 0.5 wt %. The reaction is carried out at 45—60°C under 100—300 kPa (15—44 psi). The reaction solvent is far above the boiling point of acetaldehyde, but the reaction is so fast that Httle escapes unoxidized. This temperature helps oxygen absorption, reduces acetaldehyde losses, and inhibits anhydride hydrolysis. 

Common catalyst compositions contain oxides or ionic forms of platinum, nickel, copper, cobalt, or palladium which are often present as mixtures of more than one metal. Metal hydrides, such as lithium aluminum hydride [16853-85-3] or sodium borohydride [16940-66-2] can also be used to reduce aldehydes. Depending on additional functionahties that may be present in the aldehyde molecule, specialized reducing reagents such as trimethoxyalurninum hydride or alkylboranes (less reactive and more selective) may be used. Other less industrially significant reduction procedures such as the Clemmensen reduction or the modified Wolff-Kishner reduction exist as well. 

The conversion of CO to CO2 can be conducted in two different ways. In the first, gases leaving the gas scmbber are heated to 260°C and passed over a cobalt—molybdenum catalyst. These catalysts typically contain 3—4% cobalt(II) oxide [1307-96-6] CoO 13—15% molybdenum oxide [1313-27-5] MoO and 76—80% alumina, JSifDy and are offered as 3-mm extmsions, SV about 1000 h . On these catalysts any COS and CS2 are converted to H2S. Operating temperatures are 260—450°C. The gases leaving this shift converter are then scmbbed with a solvent as in the desulfurization step. After the first removal of the acid gases, a second shift step reduces the CO content in the gas to 0.25—0.4%, on a dry gas basis. The catalyst for this step is usually Cu—Zn, which may be protected by a layer of ZnO. 

HydrometallurgicalProcesses. HydrometaHurgical refining also is used to extract nickel from sulfide ores. Sulfide concentrates can be leached with ammonia (qv) to dissolve the nickel, copper, and cobalt sulfides as amines. The solution is heated to precipitate copper, and the nickel and cobalt solution is oxidized to sulfate and reduced, using hydrogen at a high temperature and pressure to precipitate the nickel and cobalt. The nickel is deposited as a 99 wt % pure powder. 

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. 

The cobalt deposition rate on new, replacement, or decontaminated recirculation piping surface has been reduced by pretreating the piping using an atmosphere of oxygenated wet steam to form an oxide film (25). Studies have been conducted for both PWRs and BWRs to reduce the cobalt content of materials used in the nuclear parts of the plants, particularly in hardened and wear surfaces where cobalt-base alloys ( 50% Co) are used (26). Some low cobalt materials have been developed however, the use of the materials is limited to replacement parts or new plants. 

Linear terminal olefins are the most reactive in conventional cobalt hydroformylation. Linear internal olefins react at less than one-third that rate. A single methyl branch at the olefinic carbon of a terminal olefin reduces its reaction rate by a factor of 10 (2). For rhodium hydroformylation, linear a-olefins are again the most reactive. For example, 1-butene is about 20—40 times as reactive as the 2-butenes (3) and about 100 times as reactive as isobutylene. 

Eastman Chemical Co. uses only cobalt and bromine, and lower temperature oxidations are held at 175—230°C (83). Solution of 4-formylbenzoic acid is obtained by using hydroclones to replace the mother hquor from the first oxidation with fresh acetic acid. A residence time of up to 2 h is used in order to allow for sufficient digestion to take place and to reduce the 4-formylbenzoic acid content to 40—270 ppm (83). Recovery of dry terephthahc acid is as described above. 

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