Cohalt oxide

A silver-gauze catalyst is still used in some older processes that operate at a relatively higher temperature (about 500°C). New processes use an iron-molyhdenum oxide catalyst. Chromium or cohalt oxides are sometimes used to dope the catalyst. The oxidation reaction is exothermic and occurs at approximately 400-425 °C and atmospheric pressure. Excess air is used to keep the methanol air ratio helow the explosion limits. Figure 5-6 shows the Haldor Topsoe iron-molyhdenum oxide catalyzed process. 

Highly cubic ordered cobalt oxides have been successfully synthesized from KlT-6 by an accurately controlled incipient wetness approach. The adding volume of cobalt nitrate and absolute ethanol were determined by the pore volume of KIT-6, and the synthesis procedure is effective and economical. Furthermore, the obtained mesoporous cobalt oxides have better mesostructure comparing with those of former reports. The X-ray diffraction, N2 sorption isotherms, transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS) and Fourier-transform infrared spectroscopy were used to characterize the as-synthesized mesoporous cohalt oxides. 

Heaton (1928) records that cohalt oxide forms an intense and beautiful black , noting that it is used to some extent in fresco painting . Mayer (1991) describes this as a rather coarse black powder . This colour (as black oxide of cobalt ) was found in the paintbox belonging to Joseph Southall (1861-1944). Dunkerton (1980) states that this is a potter s colour which was made by Sir William Burton in collaboration with. .. John Batten and available through the society of tempera painters and Lechertier Barbe , thereby being also known as Burton s cobalt. See cobalt oxides and hydroxides group. 

In some parts of the world, as in Russia, fermented alcohol can serve as a cheap source for hutadiene. The reaction occurs in the vapor phase under normal or reduced pressures over a zinc oxide/alumina or magnesia catalyst promoted with chromium or cohalt. Acetaldehyde has been suggested as an intermediate two moles of acetaldehyde condense and form crotonaldehyde, which reacts with ethyl alcohol to give butadiene and acetaldehyde. 

Cyclohexane is oxidized in a liquid-phase process to a mixture of cyclohexanone and cyclohexanol (KA oil). The reaction conditions are 95-120°C at approximately 10 atmospheres in the presence of a cohalt acetate and orthohoric acid catalyst system. About 95% yield can be obtained ... 

Oxidizing toluene in the liquid phase over a cohalt acetate catalyst produces henzoic acid. The reaction occurs at about 165°C and 10 atmospheres. The yield is over 90% ... 

The superoxide anion radical and hydrogen peroxide are not particularly harmful to cells. It is the product of hydrogen peroxide decomposition, the hydroxyl radical (HO ), that is responsible for most of the cytotoxicity of oxygen radicals. The reaction can he catalyzed hy several transition metals, including copper, manganese, cohalt, and iron, of which iron is the most ahimdant in the human body (Reaction 2 also called the Fenton reaction). To avoid iron-catalyzed reactions, iron is transported and stored chiefly as Fe(III), although redox active iron can be formed in oxidative reactions, and Fe(III) can be reduced by semiquinone radicals (Reaction 3). 

Cobalt(II) acetate is prepared hy dissolving cohalt(II) carbonate or hydroxide in dilute acetic acid, followed by crystaUization. Also, it may be prepared by oxidation of dicobalt octacarbonyl in the presence of acetic acid. 

Two polarographic methods have been developed for the determination of cohalt(II) at concentrations ranging from approximately 1 to 80 mM in an aqueous sample. For the first method [15], which is suitable for samples containing large amounts of nickel]11), the cobalt(II) is oxidized to Co(NH3)6 in an ammoniacal medium with the aid of sodium perborate, after which the cobalt(III) species is determined. A second procedure [16] entails the use of lead dioxide in an acetic acid-acetate buffer containing oxalate to convert cobalt(II) to the 0(0204)3 ion, which can be subjected to polarographic reduction. This latter approach is well suited to the determination of cobalt in the presence of copper(II), iron(III), nickel(II), tin(IV), and zinc(II), whereas the chief interferences are cerium, chromium, manganese, and vanadium. 

Calculated total amount of co-balt(II) oxidized to cohalt(lll)... 

Emerald.—The emerald is very easy to imitate. That which succeeds best rosidts from the mixture of the oxide of copper with colorless strass. If oxide of cohalt he added, the green obtained presents blue reflexions. The composition which gives the best imitation of natural emerald is as follows —... 

Figure 9. Mixing effect of cohalt with manganese on the oxidation of hydrocarbons at NaBr/metal = 2/1 in acetic acid...

In aqueous solutions and in the absence of contplexing agents, cohalt compounds are stahlc only in the 2+ oxidation (cobaltous) state. In the complexcd state the cobaltous ion is relatively unstable, being readily oxidized to the 3+ oxidation (cohallic) slate. An extremely large number of 3-t- complex ions have been idenlilied. most of which are quite stable in aquenus media... 

Cohalt and oxygen form two stable oxides, cobulums oxide, CoO, stahlc belosv 200"C and above 9oxidizes partially, or completely, to Co.iOj. 

A. J. Balard found that stannous oxide ia oxidized to stannic oxide, and the latter ia not altered by hypochloroua acid chromic oxide is oxidized to chromic swiid mcmganese, nickel, cohalt, and lead oxides are also converted into peroxides by hypochlorous acid bismuth oxide and manganese dioxide are not altered by this acid. 

C. F. Raimnelsberg failed to prepare a cohalt periodate, but always obtained a mixture of oxide and iodate. 

The process gas from the combustion chamber is cooled in the waste heat boiler to the temperature required for the first reactor of ca. 300°C. In this reactor, filled with a cohalt-molybdenum catalyst (on an aluminum oxide support), the conversion of up to 80 to 85% of the hydrogen sulfide is carried out. After condensing out the sulfur formed at temperatures below 170°C, the temperature of the reaction gases is increased to the reaction temperature of the second reactor (ca. 220°C), which contains a highly active aluminum oxide catalyst with a large surface area (200 to 300 m /g) in which the residual hydrogen sulfide and sulfur dioxide react with one another. 

Toluene is oxidized in die liquid phase in the presence of a soluble cohalt-based catalyst The neutralization of benzoic add by potash yields insoluble potassium benzoate, which is separated by centrifuging. The disproportionation of potassium benzoate takes place between 400 and 430 C, under C02 pressure ranging from 13 to 3.106 Pa absolute, in the presence of a catalyst consisting of cadmium or zinc oxides. The reaction takes place in the solid phase. Tercphthalic add is released from its salt by the action of sulfuric add. 

Figure 5. Activity of cohalt in solutions from which manganese oxides are being precipitated...

This metal is occasionally found native, but it is chiefly met with in combination with cohalt, nickel, and iron. When the arseniurets of these metals are heated to redness in a current of air, a great part of the arsenic, being volatile, rises in vapour, and is deposited in the cold part of the chimney in the form of white oxide of arsenic or arsenious acid, the well-known white arsenic of commerce. This substance is mixed with charcoal or black flux (a mixture of charcoal with carbonate of potash), and the mixture introduced into a medicine phial, filling it about one-third. The phial is then placed in sand, the sand reaching as high as the mixture, and gradually heated to low redness. The metal sublimes and condenses in he upper part of the phial, which, when cold, may be cut off. 

One final interesting point about sulphidation is that, because the free energies of formation of the sulphides of iron, nickel, cohalt, chromium, and alvuninium are quite similar, selective sulphidation of chromium and aluminium is not favoured as in the case of oxidation. Lai has reviewed the literature of the sulphidation of alloys and has made several generalizations as follows. 

FIGURE 2.4 Preparation of layered double hydroxides (LDH). The thickness of the Nlj COyOj slab varies with the oxidation state of nickel and cohalt (From Ref. 11, 7. Solid State Chem., 104 (1993) 345. 1992 Elsevier). 

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 Ni +, 95 g S04 , 35 g Na" ", 55 g Cl , and 16 g boric acid, and the temperature was 60 °C. The current density of the process was 16A/sq.ft (approximately 170 A m ) and the cell voltage was about 1.6 V. At the normal cell operating voltage, the principal impurities - iron, cohalt, 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 shme. The produced cathodes... 

The action of redox metal promoters with MEKP appears to he highly specific. Cohalt salts appear to he a unique component of commercial redox systems, although vanadium appears to provide similar activity with MEKP. Cohalt activity can he supplemented hy potassiiun and zinc naphthenates in systems requiring low cin-ed resin color lithium and lead naphthenates also act in a similar role. Quatemaiy ammonium salts (14) and tertiary amines accelerate the reaction rate of redox catalyst systems. The tertiary amines form beneficial complexes with the cobalt promoters, facilitating the transition to the lower oxidation state. Copper naphthenate exerts a imique influence over cin-e rate in redox systems and is widely used to delay cure and reduce exotherm development during the cross-linking reaction. 

Pentaamminechlorocobaltdll) chloride, [Co(NH3]s(CI)]Cl2, is a compound that oontains cohalt in the +3 oxidation state [left). Hexaaquacohalt(II) chloride, [Co(OH2)e]CI2, oontains cobalt in the +2 oxidation state right). 

One of the routes was the low temperature decomposition of CHHP with the addition of cobalt to the oxidation mixture. The problem of fast deactivation of the cobalt catalyst could partly be solved by introducing a water wash to remove the dibasic acids that were responsible for the fast precipitation of the cobalt catalyst. Nevertheless, even after adding the cohalt catalyst to later stages of the decomposition section, a fraction of the CHHP still remained unconverted. The selectivity losses were caused by radicals obtained from the cobalt-catalysed decomposition of CHHP, which not only reacted with the available cyclohexane, but also with the desired reaction products cyclohexanone and cyclohexanol. Such one-phase decomposition has recently been industrially implemented. 

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