CORRELATION BETWEEN ARRHENIUS KINETIC-PARAMETERS IN THE REACTION OF DIFFERENT CARBON MATERIALS WITH OXYGEN

Correlation between Arrhenius kinetic parameters is often found in coal and char reactions, to such an extent that Essenhigh and Misra have recently suggested (Essenhigh, R. H.; Misra, M. K. Energy Fuels 1990, 4, 171-177) that these parameters are autocorrelated. In order to throw additional light on this point, a self-consistent set of kinetic data for the reaction of carbonaceous solids with oxygen, determined by thermogravimetric analysis, is presented and analyzed in this work. The wide range of carbon materials under study allowed to broaden the scope of correlations with respect to numerous previous studies of this reaction. A generalized correlation between Arrhenius parameters (apparent activation energy and preexponential factor) was found. Unlike previous reports, existence of a systematic curvature in the correlation plot was detected. Thus, optimum fitting to a curve obeying a power equation rather than to a straight line was attempted. An active-centers model adapted to the graphite structure was used to justify the occurrence of compensation effect, differences in behavior among carbon materials being explained as a function of the relative predominance of the various types of factors controlling the reactivity of these solids against oxygen.