Sulfur removal methods were developed using analytical-scale supercritical fluid extraction (SFE) under pyrolysis (450ยฐC) conditions on a bituminous coal sample (IBC-101) obtained from the Illinois Basin Coal Sample Program (IBCSP) and on physically cleaned Indiana No. 3 coal samples from AMAX Research and Development Center. Approximately one-half of the total sulfur was removed from IBC-101 using supercritical CO, (40.53 MPa) under pyrolysis-SFE conditions. Using on-line SFE gas chromatographymass spectrometry (SFE-g.c.-m.s.
), the major organic sulfur forms removed by pyrolysis-SFE were identified as alkyl-thiophenes (C&2,). When phosphoric acid was added to the coal prior to pyrolysis-SFE, about 80% of the total sulfur was removed from both coals regardless of whether the sulfatic sulfur, or both the sulfatic and pyritic sulfur, were removed (by HCl and HNO, extraction, respectively) prior to pyrolysis-SFE. These results demonstrate that the major fraction of sulfatic, pyritic and organic sulfur were extracted in the presence of phosphoric acid. In contrast, pyrolysis&FE with CO,-methanol appears to preferentially extract organic sulfur species, since only about 60% of the total sulfur was removed from the raw coal by pyrolysis-SFE using CO, modified with 10% methanol, while about 80% of the total sulfur was extracted if the sulfatic and pyritic sulfur were removed prior to extraction.