Cobalt oxidation reactions

Metals. Transition-metal ions, such as iron, copper, manganese, and cobalt, when present even in small amounts, cataly2e mbber oxidative reactions by affecting the breakdown of peroxides in such a way as to accelerate further attack by oxygen (36). Natural mbber vulcani2ates are especially affected. Therefore, these metals and their salts, such as oleates and stearates, soluble in mbber should be avoided. 

On the other hand, the catalytic oxidation of a n-butane, using either cobalt or manganese acetate, produces acetic acid at 75-80% yield. Byproducts of commercial value are obtained in variable amounts. In the Celanese process, the oxidation reaction is performed at a temperature range of 150-225°C and a pressure of approximately 55 atmospheres. ... 

Chromium compounds as catalysts, 188 Chromium oxide in catalytic converter, 62 Chromium oxide catalysts, 175-184 formation of active component, 176,177 of Cr-C bonds, 177, 178 propagation centers formation of, 175-178 number of, 197, 198 change in, 183, 184 reduction of active component, 177 Clear Air Act of 1970, 59, 62 Cobalt oxide in catalytic converter, 62 Cocatalysts, 138-141, 152-154 Competitive reactions, 37-43 Copper chromite, oxidation of CO over, 86-88... 

Hi) Cobalt formate. There is evidence that the kinetics of decomposition of cobalt formate [1026,1027] are similar to those of the nickel salt, considered in some detail below. A significant point of difference, however, is that metal production during reaction of the former is preceded by formation of cobalt oxides [1028]. 

It was found that the value of F, is markedly increased by ions which are effective catalysts of oxidation reactions of peroxydisulphate. These are silver(I) copper(n), and iron(III). Cobalt(II) and nickel(II) ions, although they are good catalysts for the decomposition of hydrogen peroxide, exert their effect merely as inert electrolytes in the induced reaction. Therefore it can be concluded that, in this process, activation of the rather less reactive 8203 is more important than that of hydrogen peroxide . ... 

Calciothermic reduction of samarium oxide, in the presence of cobalt powder, yields samarium-cobalt alloys in the powder form. The process is popularly known as reduction diffusion. Samarium oxide, mixed with cobalt powder and calcium hydride powder or calcium particles, is heated at 1200 °C under 1 atm hydrogen pressure to produce the alloys. Cobalt oxide sometimes partly replaces the cobalt metal in the charge for alloy preparation. This presents no difficulty because calcium can easily reduce cobalt oxide. A pelletized mixture of oxides of samarium and cobalt, cobalt and calcium, with the components taken in stoichiometric quantities, is heated at 1100-1200 °C in vacuum for 2 to 3 h. This process is called coreduction. In reduction diffusion as well as in coreduction, the metals samarium and/or cobalt form by reduction rather quickly but they need time to form the alloy by diffusion, which warrants holding the charge at the reaction temperature for 4 to 5 h. The yield of alloy in these processes ranges from 97 to 99%. Reduction diffusion is the method by which most of the 500 to 600 t of the magnetic samarium-cobalt alloy (SmCOs) are produced every year. 

Since the reaction between hydrogen and oxygen is very slow at room temperature, catalysts are incorporated in the carbon electrodes. At the anode, suitable catalysts are finely divided into platinum or palladium at the cathode, cobaltous oxide, or silver. The two halfreactions shown above yield the overall result as ... 

The more active cobalt catalyst for pyrolytic reactions was prepared by microwave calcination of cobalt nitrate which was converted to cobalt oxide by rapid microwave heating [7]. 

The oxidation of cobalt metal to inactive cobalt oxide by product water has long been postulated to be a major cause of deactivation of supported cobalt FTS catalysts.6 10 Recent work has shown that the oxidation of cobalt metal to the inactive cobalt oxide phase can be prevented by the correct tailoring of the ratio Ph2cJPh2 and the cobalt crystallite size.11 Using a combination of model systems, industrial catalyst, and thermodynamic calculations, it was concluded that Co crystallites > 6 nm will not undergo any oxidation during realistic FTS, i.e., Pi[,()/I)i,2 = 1-1.5.11-14 Deactivation may also result from the formation of inactive cobalt support compounds (e.g., aluminate). Cobalt aluminate formation, which likely proceeds via the reaction of CoO with the support, is thermodynamically favorable but kinetically restricted under typical FTS conditions.6... 

All oxidation reactions are coupled to reduction reactions. In many cases redox reactions can also involve or be affected by changes in the surrounding environment, such as changes in the pH or temperature (i.e., endothermic or exothermic reactions). Many elements in the subsurface can exist in various oxidation states, some examples include elements like carbon, nitrogen, oxygen, sulfur, iron, cobalt, vanadium, and nickel. 

The early work of Bienstock ( ) at 625°F showed manganese, copper and cobalt oxides to be active. But these materials have not been used for the UltraCat Process probably because of the adverse effect on the cracking reactions. 

The oxidation of propene to acrolein has been one of the most studied selective oxidation reaction. The catalysts used are usually pure bismuth molybdates owing to the fact that these phases are present in industrial catalysts and that they exhibit rather good catalytic properties (1). However the industrial catalysts also contain bivalent cation molybdates like cobalt, iron and nickel molybdates, the presence of which improves both the activity and the selectivity of the catdysts (2,3). This improvement of performances for a mixture of phases with respect to each phase component, designated synergy effect, has recently been attributed to a support effect of the bivalent cation molybdate on the bismuth molybdate (4) or to a synergy effect due to remote control (5) or to more or less strong interaction between phases (6). However, this was proposed only in view of kinetic data obtained on a prepared supported catalyst. 

The liquid-phase oxidation of acrolein (AL), the reaction products, their routes of formation, reaction in the absence or presence of catalysts such as acetylacetonates (acac) and naphthenates (nap) of transition metals and the influence of reaction factors were discussed in an earlier paper (22). The coordinating state of cobalt acetylacetonate in the earlier stage of the reaction depends on the method of addition to the reaction system (25, 26). The catalyst, Co(acac)2-H20-acrolein, which was synthesized by mixing a solution of Co(acac)2 in benzene with a saturated aqueous solution, decreases the induction period of oxygen uptake and increases the rate of oxygen absorption. The acrolein of the catalyst coordinated with its cobalt through the lone pair of electrons of the aldehyde oxygen. Therefore, it is believed that the coordination of acrolein with a catalyst is necessary to initiate the oxidation reaction (10). 

In all cases, the oxidation rate was smallest for experiments involving thiophenol and ferf-butanethiol. The oxygen uptake vs. time curves for cobalt-catalyzed reactions showed an initial high slope followed by a decrease in slope after ca. 30% reaction to a final steady value. 

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