Free radicals in coals and coal conversion. 2. Effect of liquefaction processing conditions on the formation and quenching of coal free radicals

Free radicals are generally accepted as playing an important role in the liquefaction of coal. In a continuing series of studies, we are attempting to determine the relation between the nature and properties of free radicals and process variables such as residence time in a reactor, heating rates to achieve highest temperature and the role of various solvents and gases in stabilizing free radicals in lower-molecular-weight moieties. The free radical concentration after thermal treatments correlates well with the propensity of a given solvent to donate its hydrogen.