Process carbon reductions

Most of the time we are concerned only with whether a particular reaction is an oxidation or reduction rather than with determining the precise change m oxidation num ber In general Oxidation of carbon occurs when a bond between carbon and an atom that IS less electronegative than carbon is replaced by a bond to an atom that is more electronegative than carbon The reverse process is reduction... 

Two processes, developed for the direct processing of lead sulfide concentrates to metallic lead (qv), have reached commercial scale. The Kivcet process combines flash smelting features and carbon reduction. The QSL process is a bath-smelting reactor having an oxidation 2one and a reduction 2one. Both processes use industrial oxygen. The chemistry can be shown as follows ... 

Thermal Reduction. MetaUic sodium is produced by thermal reduction of several of its compounds. The eadiest commercial processes were based on the carbon reduction of sodium carbonate (46—49) or sodium hydroxide (1,8,50) ... 

Because of its high reactivity, production of barium by such processes as electrolysis of barium compound solution or high temperature carbon reduction is impossible. Electrolysis of an aqueous barium solution yields Ba(OH)2, whereas carbon reduction of an ore such as BaO produces barium carbide [50813-65-5] BaC2, which is analogous to calcium carbide (see Carbides). Attempts to produce barium by electrolysis of molten barium salts, usually BaCl25 met with only limited success (14), perhaps because of the solubiUty of Ba in BaCl2 (1 )-... 

Stable oxides, such as those of clrromium, vanadium and titanium cannot be reduced to the metal by carbon and tire production of these metals, which have melting points above 2000 K, would lead to a refractoty solid containing carbon. The co-reduction of the oxides widr iron oxide leads to the formation of lower melting products, the feno-alloys, and tlris process is successfully used in industrial production. Since these metals form such stable oxides and carbides, tire process based on carbon reduction in a blast furnace would appear to be unsatisfactory, unless a product samrated with carbon is acceptable. This could not be decarburized by oxygen blowing without significairt re-oxidation of the refractory metal. 

Although this chemistry is complex, the basic process is reduction of iron oxide by carbon in an atmosphere depleted of oxygen. Archaeologists have found ancient smelters in Africa (in what is now Tanzania) that exploited this chemistry to produce iron in prehistoric times. Early African peoples lined a hole with a fuel of termite residues and added iron ore. Chamed reeds and charcoal provided the reducing substance. Finally, a chimney of mud was added. When this furnace was fired, a pool of iron collected in the bottom. 

Carbonylation of 4-en-2-ynyl carbonates offers a novel synthetic method for cross-conjugated 4-oxo-5-alkylidene-2-cyclopentenecarboxylates (Scheme 16.35) [38]. The primary product of the process appears to be a 2-vinyl-2,3-dienyl ester, leading to a palladacycle, which in turn follows CO insertion into the Pd-sp2 carbon, reductive elimination of Pd(0) species and isomerization, leading to the final product. 

High temperature carbon reduction (Lucke et al. 2005). The technique is based on indnctive high temperatnre heating (>1,500°C ) leading to carbon monoxide. It enables complete dehydration and decomposition in a single continuous process. 

Carbon-oxygen bonds adjacent to an aromatic ring or an alkene function can be cleaved by reduction at very negative potentials [1]. The process is often followed by reduction of the activating group as in 1. In these processes, the reduction potential of the activating group controls the electrode potential required. Thus an... 

Apart from the reactions included in Section IV.A, other processes, including reductive carbon-carbon cleavage with less synthetic importance, will be considered. 

Bismuth may be obtained from other ores, too. The recovery process however, depends primarily on the chemical nature of the ores. For example, the sulfide ore requires smelting, carbon reduction, and the addition of iron (to decompose any bismuth sulfide present). Oxide ores, on the other hand, are treated with hydrochloric acid to leach bismuth from the mineral. The bismuth chloride solution is then diluted with water to precipitate bismuth oxy-... 

Most potassium iodate, KIO3, is separated from the product mixture by crystallization and filtration. Remaining iodates are removed by evaporation of the solution and other processes, such as carbon reduction or thermal decompostion at 600°C to iodide ... 

Thermal decomposition of the primary ammonia species present on fly ash occurs at temperatures higher than 434 °C, thus the thermal beneficiation processes described previously (i.e., CBO and MCB) effectively remove ammonia. Several other thermal processes are also described in the literature (Harald Ruegg 1994 Fisher et al. 1997), but unlike CBO and MCB, they address the removal of ammonia only and not the carbon reduction. 

Silicones are made by hydrolysis of organochlorosilanes RnSiCl4-n, which are produced from elemental silicon (obtainable from the carbon reduction of silica, i.e., sand, Section 17.7) by the Rochow process ... 

Synthetic Rutile. In contrast to ilmenite, only a small number of rutile deposits can be mined economically, and the price of natural rutile is therefore high. Consequently, many different processes have been developed to remove the iron from ilmenite concentrates without changing the grain size of the mineral because this is highly suitable for the subsequent fluidized-bed chlorination process. All industrial processes involve reduction of Fe3+ with carbon or hydrogen, sometimes after preliminary activation of the ilmenite by oxidation. Depending on the reducing conditions, either Fe2 + is formed in an activated ilmenite lattice, or metallic iron is produced. 

The cathode mix is a compressed mixture of electrolytic Mn02 (EMD) and synthetic graphite or acetylene black to provide electronic conductivity, in a ratio of 4—5 1, wetted with electrolyte. The cathode current collector is generally the external steel can, which may be nickel-plated or coated with conductive carbon. Reduction of Mn02 in alkaline conditions is a complex process and follows a number of steps which can be written formally as... 

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