Reducing agents carbon monoxide

Carbon monoxide is also useful as a reducing agent. It is used in metallurgy to obtain metals from their oxides. For example, during iron and steel production coke in a blast furnace is converted to carbon monoxide. The carbon monoxide reduces the Fe3+ in the iron (III) oxide contained in the iron ore to produce elemental iron according to the reaction Fe20... 

Carbon monoxide reduces aromatic nitro compounds when iron pentacarbonyl is used as catalyst." A direct homogeneous catalytic reduction of nitro derivatives with water under moderate carbon monoxide pressure also occurs when rhodium carbonyl derivatives in aqueous organic bases are used as catalysts (equation 21). Presumably hydridorhodium carbonyl species are the active agents whose preferred formation in aqueous organic base may be analogous to that of iron carbonyl hydrides. 

The mineral acids decompose it into HaO and carbon monoxid. Oxidizing agents convert it into HaO and carbon dioxid. Alkaline hydroxids decompose it with formation of a carbonate and liberation of H. It acts as a reducing agent with the salts of the noble metals. 

Reference to Figure 3.4 shows that the reduction is not feasible at 800 K. but is feasible at 1300 K. However, we must remember that energetic feasibility does not necessarily mean a reaction will go kinetic stability must also be considered. Several metals are indeed extracted by reduction with carbon, but in some cases the reduction is brought about by carbon monoxide formed when air, or air-oxygen mixtures, are blown into the furnace. Carbon monoxide is the most effective reducing agent below about 980 K, and carbon is most effective above this temperature. 

Lead(II) oxide is easily reduced to the metal when heated with a reducing agent such as hydrogen, carbon or carbon monoxide, for example ... 

The process of extraction requires first smelting (to obtain the crude metal) and then refining. In smelting, iron ore (usually an oxide) is mixed with coke and limestone and heated, and hot air (often enriched with oxygen) is blown in from beneath (in a blast furnace). At the lower, hotter part of the furnace, carbon monoxide is produced and this is the essential reducing agent. The reduction reactions occurring may be represented for simplicity as ... 

In primary smelting, carbon (in the form of coal or fuel oil) is the reducing agent. During heat-up, carbon monoxide is formed by reaction with... 

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 ... 

Low Oxidation State Chromium Compounds. Cr(0) compounds are TT-bonded complexes that require electron-rich donor species such as CO and C H to stabilize the low oxidation state. A direct synthesis of Cr(CO)g, from the metal and CO, is not possible. Normally, the preparation requires an anhydrous Cr(III) salt, a reducing agent, an arene compound, carbon monoxide that may or may not be under high pressure, and an inert atmosphere (see Carbonyls). 

With less active metals, a chemical reducing agent can be used to reduce a metal cation to the element. The most common reducing agent in metallurgical processes is carbon, in the form of coke or, more exactly, carbon monoxide formed from the coke. 

Tricarbonyl(chloro)cyclopentadienylmolybdenum 6 reacts with 3-bromo-l-propene under phase transfer conditions at 45 °C to give directly the dicarbonyl(j)3-2-propenyl) complex 8 whereas at lower temperature the tricarhonyl(>/I-2-propenyl) complex 7 is obtained14. It was proposed that the carbon monoxide acts as the reducing agent. 

Because it can be further oxidized, carbon monoxide is a reducing agent. It is used in the production of a number of metals, most notably iron in blast furnaces (Section 16.13) ... 

When dicobalt octacarbonyl, [Co(CO)4]2, is the catalyst, the species that actually adds to the double bond is tricarbonylhydrocobalt, HCo(CO)3. Carbonylation, RCo(CO)3- -CO—>RCo(CO)4, takes place, followed by a rearrangement and a reduction of the C—Co bond, similar to steps 4 and 5 of the nickel carbonyl mechanism shown in 15-30. The reducing agent in the reduction step is tetra-carbonylhydrocobalt HCo(CO)4, ° or, under some conditions, H2. When HCo(CO)4 was the agent used to hydroformylate styrene, the observation of CIDNP indicated that the mechanism is different, and involves free radicals. Alcohols can be obtained by allowing the reduction to continue after all the carbon monoxide is... 

The last-mentioned line intersects the metal oxide line at a lower temperature than the line corresponding to the formation of carbon monoxide at 1 atm. It is, therefore, clear that the minimum temperature required for the carbothermic reduction of the metal oxide under vacuum is less than the minimum temperature for the same reaction at atmospheric pressure. Thus, by increasing the temperature and decreasing the pressure of carbon monoxide, it may be possible to reduce carbothermically virtually all the oxides. This possibility has been summarized by Kruger in the statement that at about 1750 °C and at a carbon monoxide pressure below 1CT3 atm, carbon is the most efficient reducing agent for oxides. 

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