BEHAVIOR OF SULFUR IN HIGH-SULFUR COAL IN A SUPERACIDIC MEDIUM WITHOUT GASEOUS-HYDROGEN

A Bronsted superacid, trifluoromethanesulfonic acid (TFMS), was found to desulfurize a lignite in the presence of a hydrocarbon without gase ous hydrogen at 150-200 degrees C under autogenous pressure of 2.6-6.6 MPa. Removal of sulfur from the coal depended on the solvent, TFMS co ncentration and reaction temperature. TFMS alone without solvent remov ed only 5.3% of sulfur as H2S, increasing the thiophenic sulfur conten t of the coal. In contrast, TFMS in toluene achieved 35.4-41.3% desulf urization, mainly from sulfides. Toluene in the presence of TFMS behav es as hydrogen donor to eliminate sulfidic sulfur as HIS, while preven ting acidic cyclization of sulfides to thiophenes. (C) 1997 Elsevier S cience Ltd.