Oxygen transfer and carbon gasification in the reaction of different carbons with CO2

The oxidation of carbon in CO2-CO mixtures can be discussed assuming the mechanism CO2 = CO + O (adsorbed) (1) O (adsorbed) + C → CO (2) This treatment is supported and supplemented by measurements of both partial reactions at different carbons, electrode graphite, charcoal, natural graphite and iron doped graphite. From the kinetics it can be seen that the reactions (1) and (2) predominantly take place at different sites. Nevertheless the kinetics of both reactions are correlated, since a uniform oxygen activity is established at the carbon surface by the interplay of the oxygen surface diffusion and of both reactions. The rate of reaction (2) and accordingly the rate of the overall reaction is proportional to the stationary oxygen activity which can be calculated from the steady state condition for oxygen adsorption. Several rate equations are derived for the overall reaction at special reaction conditions and for different carbons and it is shown that no general explicit rate equation can be given for the oxidation of carbon in CO2.