SELECTIVE OXIDATION PRETREATMENTS FOR THE ENHANCED DESULFURIZATION OFCOAL

The desulfurization of selectively oxidized coals and unoxidized contr ol coals was investigated using mild pyrolysis and various base treatm ents. Both an Illinois No. 6 and an Indiana No. 5 coal were selectivel y oxidized with peroxyacetic acid in the pretreatment step and then tr eated with various hydroxide and carbonate bases, using either water, methanol or ethanol as the solvent. Reaction variables investigated in clude reaction temperature, reaction time, pyrolysis pressure, and the level of oxidation in the pretreatment step. In general, it was found that selective oxidation, when combined with subsequent desulfurizati on reactions, always led to greater sulfur removal. In addition, the r eactivity of the sulfur in the coal towards desulfurization was appare ntly enhanced by the selective oxidation pretreatment. Thus, the sever ity of desulfurization conditions can be reduced by employing this pre treatment. Sulfur removals of up to 95% were obtained in some cases. U sually the most effective treatments involved carbonate bases under su percritical alcohol conditions. The desulfurization of some selectivel y oxidized, sulfur containing model compounds was also observed under similar reaction conditions.