OXYGEN REMOVAL FROM COAL DURING SUPERCRITICAL WATER AND TOLUENE EXTRACTION

The kinetics of oxygen removal reactions and total hydrocarbon conversion were studied during supercritical water and toluene extraction of a subbituminous coal. The results from both water and toluene extractions correlated well with a second-order kinetic model. Comparisons were made between water and toluene extractions in terms of possible mechanistic pathways for aqueous and organic supercritical fluid reactions with coal. Supercritical water consistently gave higher hydrocarbon conversions and oxygen removal than supercritical toluene. The changes in the enthalpies of activation with degrees of completion suggest that, in addition to pyrolysis, other bond rupture reactions, most likely hydrolysis, contribute to total conversion and oxygen removal during supercritical water extraction of coal.