Free radicals in coals and coal conversion. 4. Investigation of the free radicals in selected macerals upon liquefaction

This study of the nature and role of free radicals in coals and coal conversion considers free radicals from selected macerals in the liquefaction process. High-purity macerals were liquefied to different extents at high temperature (425–480 °C) in the presence of naphthalene or tetralin and hydrogen or nitrogen. The initial concentrations of free radicals as well as the residual concentrations have been measured. The dependence of free radical concentrations on solvents, gases, and temperature is reported. Resinites show the least number of free radicals. They also liquefy almost completely under all conditions used. Fusinites have the highest concentration of residual free radicals and they are unaffected by solvent, gas or temperature changes: The vitrinites show intermediate free radical concentrations that depend very strongly on the solvent used, and on the temperature, but they are unaffected by the gas used. A correlation has been established between free radical concentration and degree of conversion.