KINETICS OF OXYGEN-CHEMISORPTION ON MICROPOROUS CARBONS

Oxygen chemisorption rates on a microporous char have been measured at temperatures of 400-550 K and at oxygen partial pressures of 0.21-1 atm by use of a thermogravimetric analyzer. The experimental data were analyzed in terms of a distributed activation energy site model, and the model can account for most of the experimental observations made in the present study. Activation energies in the range of 70-120 kJ/mol for oxygen chemisorption were calculated by use of this model. The substantial energy barrier, at the upper end of the distribution, to oxygen chemisorption on a microporous carbon was not expected. On the basis of this result, it is postulated that the rate-controlling step for the low-temperature carbon-oxygen reaction may be oxygen adsorption on these high activation energy sites.