Oxides and Carbonates

COBr2 has recently been shown to be a useful general brominating reagent for the preparation of d- and f-block bromides and oxide bromides.Thus, when V2O5 is heated with an excess of COBr2 in a sealed Car-ius tube at 125°C for 10 days, a quantitative yield of VOBr2 is obtained by a reaction that is driven thermodynamically by 

Carbon forms 2 extremely stable oxides, CO and CO2, 3 oxides of considerably lower stability, C3O2, C5O2 and C]209, and a number of unstable or poorly characterized oxides including C2O, C2O3 and the nonstoichiometric graphite oxide (p. 289). Of these, CO and CO2 are of outstanding importance and their chemistry will be discussed in subsequent paragraphs after a few brief remarks about some of the others. 

Tricarbon dioxide, C3O2, often called carbon suboxide and ponderously referred to in Chemical Abstracts as l,2-propadiene-l,3-dione, is a foul-smelling gas obtained by dehydrating malonic acid, CH2(C02H)2, at 

Direct oxidation of C in a limited supply of oxygen or air yields CO in a free supply CO2 

The nature of the bonding, particularly in CO, has excited much attention because of the unusual coordination number (1) and oxidation state (-f2) of carbon it is discussed on p. 926 in connection with the formation of metal-carbonyl complexes. 

Quantitative estimation relies on the liberation of I2 from I2O5 or (in the absence of C2H2) on absorption in an acid solution of CuCl to form the adduct [Cu(C0)Cl(H20)2]. 

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Aluminium nitride can also be prepared by heating a mixture of aluminium oxide and carbon in nitrogen in an electric arc furnace ... 

By the reaction of chlorine with a heated mixture of chrom ium(III) oxide and carbon ... 

Large copper ore deposits are found in the U.S., Chile, Zambia, Zaire, Peru, and Canada. The most important copper ores are the sulfides, the oxides, and carbonates. From these, copper is obtained by smelting, leaching, and by electrolysis. 

Acrylonitrile is combustible and ignites readily, producing toxic combustion products such as hydrogen cyanide, nitrogen oxides, and carbon monoxide. It forms explosive mixtures with air and must be handled in weU-ventilated areas and kept away from any source of ignition, since the vapor can spread to distant ignition sources and flash back. 

None of the natural sulfides of manganese are of any commercial importance. Some siUcates have been mined. Rhodonite and braunite are of iaterest because these are frequendy associated with the oxide and carbonate minerals. The chemical composition of some common manganese minerals are given ia Table 3. 

Acidic Properties. As a typical acid, it reacts readily with alkaUes, basic oxides, and carbonates to form salts. The largest iadustrial appHcation of nitric acid is the reaction with ammonia to produce ammonium nitrate. However, because of its oxidising nature, nitric acid does not always behave as a typical acid. Bases having metallic radicals ia a reduced state (eg, ferrous and staimous hydroxide becoming ferric and stannic salts) are oxidized by nitric acid. Except for magnesium and manganese ia very dilute acid, nitric acid does not Hberate hydrogen upon reaction with metals. 

Carbon Dioxide and Carbon DisulUde. Propylene oxide and carbon dioxide react ia the presence of tertiary amine, quaternary ammonium haUdes, or calcium or magnesium haUde catalysts to produce propylene carbonate (52). Use of catalysts derived from diethyUiac results ia polycarbonates (53). 

Zirconium tetrachloride, ZrCl, is prepared by a variety of anhydrous chlorination procedures. The reaction of chlorine or hydrogen chloride with zirconium metal above 300°C, or phosgene or carbon tetrachloride on zirconium oxide above 450°C, or chlorine on an intimate mixture of zirconium oxide and carbon above 700°C are commonly used. 

Zirconium tetrabromide [13777-25-8] ZrBr, is prepared direcdy from the elements or by the reaction of bromine on a mixture of zirconium oxide and carbon. It may also be made by halogen exchange between the tetrachloride and aluminum bromide. The physical properties are given in Table 7. The chemical behavior is similar to that of the tetrachloride. 

Zirconium tetraiodide [13986-26-0], Zrl, is prepared directly from the elements, by the reaction of iodine on zirconium carbide, or by halogen exchange with aluminum triiodide. The reaction of iodine with zirconium oxide and carbon does not proceed. The physical properties are given in Table 7. 

Beryllium Carbide. Beryllium carbide [506-66-17, Be2C, maybe prepared by heating a mixture of beryllium oxide and carbon to 1950—2000°C,... 

BeryUium chloride [7787-47-5], BeCl2, is prepared by heating a mixture of beryUium oxide and carbon in chloride at 600—800°C. At pressures of 2.7—6.7 Pa (0.02—0.05 mm Hg) beryllium chloride sublimes at 350—380°C. It is easily hydrolyzed by water vapor or in aqueous solutions. BeryUium chloride hydrate [14871-75-1] has been obtained by concentrating a saturated aqueous solution of the chloride in a stream of hydrogen chloride. ChloroberyUate compounds have not been isolated from aqueous solutions, but they have been isolated from anhydrous fused salt mixtures. 

On a fresh surface the metal has a steely lustre but rapidly tarnishes in air as a result of surface formation of oxide and carbonate species. For protection against oxidation the metal is usually stored in a light mineral oil. When made finely divided, eg, on being cut, it can be strongly pyrophoric, and, for this reason is used, as the ferro-alloy mischmetal, in lighter flints and ordnance. Cerium reacts steadily with water, readily dissolves in mineral acids, and is also attacked by alkafl it reacts with most nonmetals on heating. 

Oil and Metal Incendiary Mixtures. PTl is a complex mixture composed of magnesium dust, magnesium oxide, and carbon (qv), along with an adequate amount of petroleum (qv) and asphalt (qv) to form the paste (7). The U.S. developers have adopted the formula type c paste (goop),... 

Briquets of mixed, finely divided oxide and carbon are heated to 1275—1400°C in a refractory container. The minimum pressure is about 40 Pa (0.3 mm Hg) for reduction at 1400°C. Lower pressures or higher temperatures cause excessive volatilisation of chromium. The result is a high purity, low interstitial product. 

Cobalt metal is significantly less reactive than iron and exhibits limited reactivity with molecular oxygen in air at room temperature. Upon heating, the black, mixed valence cobalt oxide [1308-06-17, Co O, forms at temperatures above 900°C the oHve green simple cobalt(II) oxide [1307-96-6] CoO, is obtained. Cobalt metal reacts with carbon dioxide at temperatures greater than 700°C to give cobalt(II) oxide and carbon monoxide. 

Other Derivatives. Ethylene carbonate, made from the reaction of ethylene oxide and carbon dioxide, is used as a solvent. Acrylonitrile (qv) can be made from ethylene oxide via ethylene cyanohydrin however, this route has been entirely supplanted by more economic processes. Urethane intermediates can be produced using both ethylene oxide and propylene oxide in their stmctures (281) (see Urethane polymers). 

Boron carbide from boron oxide and carbon Calcium silicate from lime and silica Calcium carbide by reaction of lime and carbon Leblanc soda ash... 

Powdered-product collection, as in pneumatic conveying the spray drying of milk, eggs, and soap and the manufacture of nigh-purity zinc oxide and carbon black... 

Boron carbide from boron oxide and carbon... 

Figure 7.14 As in Fig. 7.13. Note the presence of orange iron oxides and carbonate. Also note how attack starts as small pits due to dropwise condensation.

Zinc occurs most abundantly in tire mineral. Sphalerite, ZnS, which is roasted to produce the oxide before the metal production stage. The products of the roast are then reduced by carbon to yield zinc oxide and CO(g). In the older process, tire Belgian retort process, the metal oxide and carbon are mixed together in a reactor which allows the indirect heating of the charge to produce the gaseous products followed by tire condensation of zinc at a lower temperature in a zone of the reactor which is outside the heating chamber. The carbon monoxide is allowed to escape from the vessel and is immediately burnt in... 

An improved approach from the point of view of thermal efficiency is the electrothermal process in which the mixture of zinc oxide and carbon, in the form of briquettes, are heated in a vertical shaft furnace using the electrical resistance of the briquettes to allow for internal electrical heating. The zinc vapour and CO(g) which are evolved are passed tluough a separate condenser, the carbon monoxide being subsequently oxidized in air. 

The destruction and removal of trichloroethylene (TCE) by reaction with OXITOX , (sodium carbonate activated by Mg and Mn oxides and carbonates), proceeds through the following stoichiometric reaction ... 

The remaining. SO percent or less ot supply must have an average emission rate below the system average for fossil-fuel-emitted sulfur dioxide, nitrogen oxide, and carbon dioxide. 

The reaction between propylene oxide and carbon dioxide produces propylene carbonate. The reaction conditions are approximately 200°C and 80 atmospheres. A yield of 95% is anticipated ... 

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