DYNAMIC INSITU 9 GHZ CW-EPR LOW-TEMPERATURE OXIDATION STUDY OF SELECTED ALBERTA COALS .3. INFLUENCE OF EXINITE MACERALS AND MOISTURE IN AN HV BITUMINOUS COAL

Dynamic in situ 9 GHz c.w.-e.p.r. has been used to study the low-temperature oxidation in the interval 20 to 250-degrees-C of hv bituminous coal samples enriched and depleted in exinite, when dried or moisture-saturated. The changes in the e.p.r. spectral parameters and relative total spin concentration are correlated with the maceral composition and moisture content of the samples. These parameters exhibit maxima at approximately 100-degrees-C. The percentage increase in the spin concentration for dried coal samples between 20 and 100-degrees-C is greater in the exinite-depleted than in the exinite-enriched sample. The 20-degrees-C free radical spin concentration is higher in dried than in moisture-saturated coals but the concentration changes more rapidly with temperature for moisture-saturated samples. This observation is in a good agreement with the interpretation of the lineshape distortion changes determined using radial difference a(o)d(o)-Argand diagrams. It is concluded that the moisture content associated with the vitrinite maceral is the most important factor in determining the rate at which the low-temperature oxidation processes occur in coal.