Boudouard reaction
The Boudouard reaction, named after Octave Leopold Boudouard, is the redox reaction of a chemical equilibrium mixture of carbon monoxide and carbon dioxide at a given temperature. It is the disproportionation of carbon monoxide into carbon dioxide and graphite or its reverse:
The Boudouard Reaction to form carbon dioxide and carbon is exothermic at all temperatures. However, the standard enthalpy of the Boudouard reaction becomes less negative with increasing temperature, as shown to the side.
While the formation enthalpy of CO
2 is higher than that of CO, the formation entropy is much lower. Consequently, the standard free energy of formation of CO
2 from its component elements is almost constant and independent of the temperature, while the free energy of formation of CO decreases with temperature. At high temperatures, the forward reaction is therefore endergonic, favoring the (exergonic) reverse reaction toward CO, even though the forward reaction is still exothermic.
The effect of temperature on the extent of the Boudouard reaction is indicated better by the value of the equilibrium constant than by the standard free energy of reaction. The value of log10(Keq) for the reaction (valid between 500–2200 K) is:
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