Sulfur Speciation in Different Kerogens by XANES Spectroscopy

Abstract

X-ray absorption near-edge structure (XANES) methodology has been employed to quantify the different sulfur structures present in three Type I and three Type II kerogens. Kerogens from the Green River (3), Bakken (1), Woodford (1), and Indiana limestone (1) formations were studied. Both aliphatic (sulfide) and aromatic (thiophene) forms of sulfur exist in all these kerogen samples. Except for Woodford, all of the kerogens contain oxidized functional groups. Sulfur in Types I and II kerogens mimics the carbon chemistry in that the sulfur structures are more aromatic in Type II than in Type I. It was impossible to differentiate elemental sulfur from pyrite in these samples by using K-edge XANES.

The Catalytic Conversion of Thiophenes over Large H‐ZSM‐5 Crystals: An X‐Ray, UV/Vis, and Fluorescence Microspectroscopic Study

“…This finding is in agreement with the widely accepted accuracy limit for sulfur XANES speciation. [27] Finally, the peak at about 2481 eV is similar to the peak found for the H-ZSM-5 zeolites and indicates the presence of sulfonates (R-SO 3 À ), which indicates that thiophene can react with oxygen when located in an acid site containing porous material (e.g., alumina, and zeolites). Taking all aforementioned observations into consideration, it can be stated that when the catalytic conversion takes place within the well-defined micropores of the H-ZSM-5 zeolites: 1) the main edge is broadened, 2) additional features appear, which could not be fitted solely with thiols and thiophenes and 3) the reaction products formed are not completely identical for the zeolites and the silica/boehmite mixtures.…”

“…Space-resolved X-ray fluorescence spectra allowed 2D elemental imaging of Si, Al, and S on individual zeolite crystals with a spot size down to 0.21 0.8 mm 2 . Furthermore, X-ray absorption near-edge spectroscopy (XANES) on selected spots gave spectroscopic data that could be used for composition analysis, [24][25][26][27] whereas UV/ X-ray absorption, UV/Vis, and fluorescence microspectroscopy have been used to characterize the catalytic conversion of thiophene derivatives within the micropores of an individual H-ZSM-5 zeolite crystal. Space-resolved information into the Si/ Al ratios and sulfur content was provided by X-ray absorption microspectroscopy.…”

Review of the Molecular Structure and Aggregation of Asphaltenes and Petroleomics

“…The asphaltene sulfur is more aromatic in more-mature oils (George and Gorbaty 1989). Sulfur is similar to carbon in other carbonaceous materials in that both become more aromatic with higher maturity (Wiltfong et al 2005;Mitra-Kirtley and Mullins 2007). Nitrogen XANES studies show that asphaltene nitrogen is virtually all in aromatic groups in pyrrolic and to a lesser extent pyridinic structures (Mitra-Kirtley et al 1993).…”

Thermal transformations of organic and inorganic sulfur in Type II kerogen quantified by S-XANES

“…S-XANES has been widely used to speciate and quantify organic forms of sulfur in kerogen (Eglinton et al, 1994;Nelson et al, 1995;Sarret et al, 2002;Wiltfong et al, 2005;Kelemen et al, 2007) and coal (Gorbaty et al, 1990;George et al, 1991;Huffman et al, 1991). S-XANES also has been used to characterize the sulfur forms in pyrolysis chars of kerogen (Riboulleau et al, 2000;Sarret et al, 2002), CrCl 2 treated hydropyrolysis kerogen chars (Nelson et al, 1995), and pyrolyzed coals Taghiei et al, 1992).…”