1. Applications
     Variations  

2. References

Carbothermal reactions produce carbon monoxide and sometimes carbon dioxide. The facility of these conversions is attributable to the entropy of reaction: two solids, the metal oxide and carbon, are converted to a new solid (metal) and a gas (CO), the latter having high entropy. Heat is required for carbothermic reactions because diffusion of the reacting solids is otherwise slow.

Applications

A prominent example is that of iron ore smelting. Many reactions are involved, but the simplified equation is usually shown as:

2{{chem|Fe|2|O|3}} + 3C → 4Fe + 3{{CO2}}

On a more modest scale, about 1 million tons of elemental phosphorus is produced annually by carbothermic reactions.^[2] Calcium phosphate (phosphate rock) is heated to 1,200–1,500 °C with sand, which is mostly {{chem|SiO|2}}, and coke (impure carbon) to produce {{chem|P|4}}. The chemical equation for this process when starting with fluoroapatite, a common phosphate mineral, is:

4{{chem|Ca|5|(PO|4|)|3|F}} + 18{{chem|SiO|2}} + 30C → 3{{chem|P|4}} + 30CO + 18{{chem|CaSiO|3}} + 2{{chem|CaF|2}}

Of historic interest is the Leblanc process. A key step in this process is the reduction of sodium sulfate with coal:^[3]

Na₂SO₄ + 2 C → Na₂S + 2 CO₂

The Na₂S is then treated with calcium carbonate to give sodium carbonate, a commodity chemical.

Variations

Sometimes carbothermic reactions are coupled to other conversions. One example is the chloride process for separating titanium from ilmenite, the main ore of titanium. In this process, a mixture of carbon and the crushed ore is heated at 1000 °C under flowing chlorine gas, giving titanium tetrachloride:

2{{chem|FeTiO|3}} + 7{{chem|Cl|2}} + 6C → 2{{chem|TiCl|4}} + 2{{chem|FeCl|3}} + 6CO

For some metals, carbothermic reactions do not afford the metal, but instead give the metal carbide. This behavior is observed for titanium, hence the use of the chloride process. Carbides also form upon high temperature treatment of {{chem|link=Chromium(III) oxide|Cr|2|O|3}} with carbon. For this reason, aluminium is employed as the reducing agent.

References

• Ben Dunne
• Bendu (Star Wars)
• Ben Dwarshuis
• Bend Whitewater Park
• Bendy and the Ink Machine
• Ben Dyball
• Bendybus
• Bendych Aym
• Bendy (disambiguation)
• Ben Eardley
• Ben Earl
• Beneath Ceaseless Skies: Literary Adventure Fantasy
• Beneath the Blue (The 69 Eyes song)
• Beneath the Flood
• Beneath the Helmet: From High School to the Home Front
• Beneath the Ice
• Beneath The Lies
• Beneath the Lion Rock
• Beneath the Lion's Gaze
• Beneath the Palms on the Blue Sea
• Beneath the Snow Encumbered Branches
• Beneath the Streetlights and the Moon
• Beneath the Sun
• Beneath the Sun (Trivium song)
• Beneath the Surface