Direct determination of sulfur chemical structures in source kerogens by x-ray absorption spectroscopy (XANES): Implications of sulfidic-rich vs. thiophenic on kerogen classification and reactivity
- Mobil Research and Development Corp., Princeton, NJ (United States)
- Univ. of Kentucky, Lexington, KY (United States); and others
Sulfur K-edge X-ray absorption near-edge structure (XANES) studies have been performed for the first time on ten {open_quote}pyrite-free{close_quote} source kerogens for the purpose of determining chemical forms present in the kerogens. In addition a suite of hydrous pyrolysis residues of a Monterey shale were evaluated to investigate organosulfur transformation during petroleum generation. Such information is important in determining approximate contribution from different sulfur structures to the overall kinetics of hydrocarbon generation from source kerogens. Because the major sulfur forms occurring in kerogens (pyrite, organic sulfide, thiophene, sulfoxide, sulfune, and sulfate) have characteristic s {r_arrow}p transition energies, the relative peak area contributed to the XANES by each sulfur form an be determined. These peak areas are converted to weight percentages of sulfur by using calibration constants derived from XANES data of standard compound mixtures. A significant number of the kerogens (66%) are found to be sulfidic-rich. The results suggest that kerogens can be further classified as sulfidic-rich vs. thiophenic. A new sulfur index (SI) defined by the ratio of sulfidic/(sulfidic + thiophenic) x % organic sulfur content is proposed as a useful parameter to determine the relative contribution of labile organosulfur structures to the general kerogen reactivity. Labile sulfur species are found to transform to stabler structures during hydrous pyrolysis. Implications of these findings to kerogen decomposition kinetics and product quality are explored.
- OSTI ID:
- 126540
- Report Number(s):
- CONF-950402--
- Country of Publication:
- United States
- Language:
- English
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