INSITU X-RAY ABSORPTION FINE-STRUCTURE SPECTROSCOPY INVESTIGATION OF SULFUR FUNCTIONAL-GROUPS IN COAL DURING PYROLYSIS AND OXIDATION

Sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy has been utilized to conduct the first direct characterization and quantification of sulfur functional groups in coal during in situ high-temperature oxidation and pyrolysis. The behavior of all major sulfur forms during such treatments was derived for two U.S. bituminous coals and a low-rank Australian brown coal from least-squares analysis of sulfur K-edge XANES spectra taken at constant temperatures up to 600-degrees-C. During pyrolysis, pyrite began to convert to pyrrhotite at temperatures above 400-degrees-C. The organic sulfides decreased significantly above 300-degrees-C, while thiophenic sulfur remained nearly constant throughout the measurements. The formation of sulfate during oxidation experiments was observed above 300-degrees-C.