Free radicals in coal and coal conversions. 10. Kinetics and reaction pathways in hydroliquefaction

Abstract The development is reported of a point rate model for the solubility fractions obtained from Powhatan No.5 coal liquefaction in terms of free-radical concentration. Stepwise regression procedures were used to determine rate constants for general hypothetical rate models. Chemical principles were used at each stage to eliminate terms and to fix others. Rate constant expressions were obtained by fitting In k to the inverse absolute temperature for each solvent. Generalized reaction paths were determined from these individual reactions by combining various reactions. These reactions described the conversion of material between solubility fractions via free-radical interactions. In all three solvents progressive liquefaction reactions that did not involve measured radicals (conventional reaction terms) predominated in the rapid break-up of coal, while free-radical reactions are predominant in retrogressive changes. At higher radical concentrations retrogressive reactions predominated. More reactions of all types became significant with increasing temperature.