BENEFICIAL-EFFECTS OF PRESWELLING ON CONVERSION AND CATALYTIC ACTIVITY DURING COAL-LIQUEFACTION

This paper describes the benefits of preswelling on coal conversion and product quality by increasing the effectiveness of dispersed catalysts. Batch autoclave experiments have shown that depositing catalysts on bituminous and lower rank coals in the presence of a coal swelling solvent, followed by removal of the solvent, enhances coal conversion and product quality during subsequent liquefaction. The extent of these benefits depends on the nature of the swelling agent and the coal rank. The improvement in product quality is manifested in increased oil yield, which is higher for the higher rank coal. The beneficial effect of swelling is attributed to the opening of the microporous structure, enabling effective dispersion of catalysts on the coal surface. Better catalyst dispersion causes more efficient hydrogen transfer to the reaction sites during the initial stages of liquefaction, thus enabling rapid capping of coal free radicals and a concomitant reduction in retrogressive reactions.