Carbothermic reaction

Carbothermal reduction of molten potassium nitrate with charcoal to potassium nitrite

Carbothermic reactions involve the reduction of substances, often metal oxides (O^2-), using carbon (C) as the reducing agent. The reduction is usually conducted in the electric arc furnace or reverberatory furnace, depending on the metal ore. These chemical reactions are usually conducted at temperatures of several hundred degrees Celsius. Such processes are applied for production of the elemental forms of many elements. The ability of metals to participate in carbothermic reactions can be predicted from Ellingham diagrams.^[1]

Carbothermal reactions produce carbon monoxide (CO) and sometimes carbon dioxide (CO₂). The facility of these conversions is attributable to the entropy of reaction: two solids, the metal oxide (and flux) and carbon, are converted to a new solid (metal) and a gas (CO_$x$), the latter having high entropy.

^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. "Figure 8.19 Ellingham diagram for the free energy of formation of metallic oxides" p. 308

[greenwood-1] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. "Figure 8.19 Ellingham diagram for the free energy of formation of metallic oxides" p. 308

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