Carbon as a reducing agent

This reaction is highly exothermic thus, it is difficult to control the reaction temperature (31). The oldest method for producing SiCl is the direct reaction of sihca and chlorine in the presence of carbon as a reducing agent (24). 

Sodium sulphate forms, in the presence of aluminium at 800°C, sodium sulphide. The reaction usually proves to be explosive and the usual method of preparing sodium sulphide from the sulphate uses carbon as a reducing agent. 

Perhaps the most important use of carbon is as a reducing agent because it is the least expensive reducing agent used on a large scale. Two of major uses of carbon as a reducing agent are the production of iron,... 

The extraction of a metal (M) from its oxide (MO) using carbon as a reducing agent is generally endothermic. As expected, experiments show that the equilibrium constants of the general reaction,... 

The formation of nitrides from oxides is performed by the aid of carbon as a reducing agent, according to the overall reaction equation... 

It is well-known that carbon as a reducing agent can not only prevent the formation of Fe impurity and the agglomeration of particles during the preparation of LiFeP04, but also increase the electronic conductivity. 

The three reactions are based on kaolin, to which in the first instance, were applied sodium sulphate and carbon as a reducing agent, in the second instance, sodium sulphate, sodium carbonate and sulphur, and in the third, silica and carbon. See Recherches et travaux, op. cit. (21), pp. 32-33. 

Titanium metal cannot be produced by reduction of Ti02 with carbon because the metal and carbon react to form titanium carbides. Also, at high temperatures the metal reacts with air to form Ti02 and TiN. The metallurgy of titanium, then, must be conducted out of contact with air and with an active metal rather than with carbon as a reducing agent. 

Since all living matter contains phosphate, P04 , in one form of another, phosphorus can in principle be obtained from any part of a plant or animal. Heating phosphate (most commonly as the calcium salt) with carbon — as a reducing agent — releases phosphorus as the volatile white phosphorus, P4 ... 

The sihcates formed in reactions 2 and 3 fuse with the added fluxes to form a Hquid slag at which point carbon monoxide loses its effectiveness as a reducing agent. Unreacted carbon from the fuel then becomes the predominant reductant in reducing both staimous siUcate to tin and ferrous siUcate to iron. The metallic iron, in turn, reduces tin from stannous siUcate ... 

Manufacture. Titanium chloride is manufactured by the chlorination of titanium compounds (1,134—138). The feedstocks usually used are mineral or synthetic mtile, beneficiated ilmenite, and leucoxenes. Because these are all oxygen-containing, it is necessary to add carbon as well as coke from either coal or fuel oil during chlorination to act as a reducing agent. The reaction is normally carried out as a continuous process in a fluid-bed reactor (139). The bed consists of a mixture of the feedstock and coke. These are fluidized by a stream of chlorine iatroduced at the base (see Fluidization). The amount of heat generated in the chlorination process depends on the relative proportions of CO2 or CO that are formed (eqs. 1 and 2), and the mechanism that... 

Hydrocinnamic Acid.—The preparation illustrates the use of sodium amalgam as a reducing agent It should be noted that hydiocinnamic acid may be also obtained from m.donic ester by acting upon the sodium compound nith benzyl chloride, then hydrolysing and removing carbon dioxide,... 

The main gaseous product is the hydrogen. Carbon can be either sequestered or used as a material commodity under less severe CO2 restraints. It can also be used as a reducing agent in metallurgical processes. From the point of view of carbon sequestration, it is easier to separate, handle, transport, and store solid carbon than CO2 [5]. 

Silicon is generally considered to be a congener of carbon and this is also reflected in the evolution of silicon as a reducing agent for metal oxides. Silicon forms a fairly stable solid oxide silica or silicon dioxide (Si02) and also a stable gaseous oxide silicon monoxide (SiO), both of which can be useful in oxide reduction reactions. 

These forms of carbon are also known to have some order, so they are not completely amorphous. When appropriately prepared (so-called activated charcoal), charcoal has an enormous surface area, so it is capable of adsorbing many substances from both gases and solutions. As was described in Chapter 11, coke is used on an enormous scale as a reducing agent in the production of metals. The "amorphous" forms of carbon can be transformed into graphite by means of the Acheson process, in which an electric current heats a rod of the "amorphous" form. 

As we have already mentioned, carbon is a reducing agent of great importance, and CO is often the oxidation product (see Eqs. (13.93) and (13.94)). The reaction of carbon with steam at high temperature also produces CO. 

Other markets for char include iron, steel, and sili-con/ferro-silicon industries. Char can be used as a reducing agent in direct reduction of iron. Ferro-silicon and metallurgical-grade silicon metal are produced carbothermally in electric furnaces. Silica is mixed with coke, either iron ore or scrap steel (in the case of ferro-silicon), and sawdust or charcoal in order to form a charge. The charge is then processed by the furnace to create the desired product. Char can be substituted for the coke as a source of reducing carbon for this process. Some plants in Norway are known to have used coal-char in the production of silicon-based metal products as late as mid-1990.5 The use of char in this industry is not practiced due to lack of char supply. 

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