Abstract
The low temperature oxidation process in dried and moisture saturated samples of an Alberta hv bituminous coal containing ~237 ppm manganese impurity ions subjected to dry air flow has been studied using dynamic in situ 9 GHz continuous wave-electron paramagnetic resonance (CW-EPR) in the temperature interval from 293 to 523 K. It was found that there is a correlation between oxidation, as indicated by an increasing concentration of carbon free radicals, and the presence of moisture and inorganic matter as monitored by the Mn 2+ spin concentration. Arrhenius plots were used to characterize the changes in the spin concentration which were observed during the low temperature oxidation process. It was found that the lower values of the apparent activation energy can be attributed to solid (carbonyl and carboxyl) rather than gaseous oxidation products, and that these activation energy values depend on the sample pretreatment procedure. This kinetic analysis also has provided evidence for the existence of reactions involving changes in the oxidation state of the Mn ions which occur in characteristic temperature intervals.
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