SULFUR SPECIATION IN BITUMENS AND ASPHALTENES BY X-RAY-ABSORPTION FINE-STRUCTURE SPECTROSCOPY

The S L-edge and K-edge XANES spectra were collected on bitumen and as phaltene samples as well as model compounds in order to determine the feasibility of monitoring transformations of organic sulphur in bitume n during genesis, processing, and upgrading. Using the spectra of mode l compounds as fingerprints, it was possible to speciate the sulphur f orms in bitumen and asphaltene. The reduced form of sulphur such as th iophenes are the predominant form of sulphur in the bitumen and asphal tene samples analyzed. No significant amounts of oxidized sulphur form s could be detected. Spectra collected using total electron yield and fluorescence yield were identical, confirming that there is no prefere ntial partitioning at the bitumen/air interface, or oxidation during s ample handling. Also important was the finding that bitumen could be a nalyzed at moderately high vacuum (10(-8) torr). Thus XANES represents a rapid, nondestructive mean of characterizing specific classes of co mpounds in complex matrices, such as bitumen.