Boudouard Carbon
Definition and meaning of Boudouard Carbon in chemistry.
Boudouard carbon is the finely divided, solid elemental carbon deposited by the Boudouard reaction, the reversible disproportionation of carbon monoxide into carbon dioxide and carbon (2 CO ⇌ CO2 + C).
In more detail
Thermodynamics favors carbon deposition (the forward, exothermic direction) at lower temperatures, roughly below 700°C, while the reverse endothermic reaction (carbon gasification by CO2) dominates at higher temperatures, as in a blast furnace. The forward reaction is slow without a catalyst, but transition metals such as iron, nickel, and cobalt catalyze it strongly, so carbon precipitates as fine particles, filaments, or whiskers on metal surfaces. This deposition drives coking (catalyst deactivation by carbon buildup) and metal dusting, a severe pitting corrosion in which carbon nucleates within the metal lattice and disintegrates it into dust.
Key facts
| Reaction | 2 CO(g) ⇌ CO2(g) + C(s) |
|---|---|
| Named after | Octave Boudouard (1905) |
| Carbon-favoring range | Below ~700°C (catalyzed by Fe, Ni, Co) |
| Field | Physical Chemistry |
In steam-methane-reforming and syngas plants, iron- and nickel-based alloy tubes carrying CO-rich process gas at 400-700°C can suffer metal dusting: Boudouard carbon deposits catalytically at grain boundaries, weakening the alloy until it crumbles into fine metal and graphite dust.
Frequently asked questions
Why does Boudouard carbon form specifically on metal surfaces?
Transition metals like iron, nickel, and cobalt catalyze CO disproportionation and allow carbon atoms to dissolve into the metal lattice before precipitating as graphitic carbon, which is why deposition and metal dusting concentrate on metal equipment rather than occurring uniformly in the gas phase.
Is Boudouard carbon formation exothermic or endothermic?
The carbon-forming direction, 2 CO to CO2 + C, is exothermic and favored at lower temperature; the reverse reaction, carbon gasification by CO2 (the Boudouard reaction run in reverse), is endothermic and favored at high temperature, which is why blast furnaces consume rather than deposit carbon.