Organically bound sulfur

A Sulfur K Edge X-ray Absorption Near Edge Structure (XANES) Spectroscopy method has been developed for the direct determination and quantification of the forms of organically bound sulfur in nonvolatile petroleum and coal samples. XANES spectra were taken of a number of model compounds, mixtures of model compounds, heavy petroleum and coal samples. Analysis of the third derivatives of these spectra allowed approximate quantification of the sulfidic and thiophenic components of the model mixtures and of heavy petroleum and coal samples. These results are compared with those obtained by X-ray Photoelectron Spectroscopy (XPS). 

XANES of Model Compounds. Table I lists the first inflection points of the sulfur K edge spectra for a series of model compounds whose structures are believed to be representative of the types of organically bound sulfur found in heavy petroleum and coals. 

Table II. Approximate Quantification of Organically Bound Sulfur Forms in Heavy Hydrocarbons...

This work has demonstrated that organically bound sulfur forms can be distinguished and in some manner quantified directly in model compound mixtures, and in petroleum and coal. The use of third derivatives of the XANES spectra was the critical factor in allowing this analysis. The tentative quantitative identifications of sulfur forms appear to be consistent with the chemical behavior of the petroleum and coal samples. XANES and XPS analyses of the same samples show the same trends in relative levels of sulfide and thiophenic forms, but with significant numerical differences. This reflects the fact that use of both XPS and XANES methods for quantitative determinations of sulfur forms are in an early development stage. Work is currently in progress to resolve issues of thickness effects for XANES spectra and to define the possible interferences from pyritic sulfur in both approaches. In addition these techniques are being extended to other nonvolatile and solid hydrocarbon materials. 

Sulfur occurs mainly in proteins that typically display a C/S ratio of about 50. The processes responsible for the direct primary production of organically bound sulfur are the direct assimilation of sulfate by living plants and microbiological assimila-tory processes in which organic sulfur compounds are synthesized. Land plants use sulfate available from precipitation, marine phytoplankton use ocean water sulfate. 

Soils contaminated with high levels of organically bound sulfur compounds require the use of additional wet scrubbing. Soils contaminated with high levels of organically bound chlorine compounds require the use of additional wet or dry scrubbing equipment. Soils containing heavy metals may require additional posttreatment processes to stabilize or remove the metals. 

Copper and copper-containing alloys are susceptible to attack by elemental sulfur and hydrogen sulfide as well as organically bound sulfur. Active or elemental sulfur and hydrogen sulfide gas can attack copper to form copper sulfide, a dark-brown to black compound. This can be seen through ASTM D-130 copper corrosion testing. 

Each of the major classifications of sulfur types may be further subdivided. The inorganically bound sulfur is conventionally subdivided among pyrite, sulfate, and sulfide types of sulphur3. Again, sulfur can transfer among these types, as well as back and forth to organically bound sulfur or escape from the solid as a gas. 

The model was designed to study the ability of sulfur-oxidizing bacteria to use the organically bound sulfur as substrate. The symmetry of the sulfides provided an insight into the sulfur abstracting prowess of T. thiooxidans. 

Gorbaty, M. L., and Kelemen, S. R. (2001). Characterization and reactivity of organically bound sulfur and nitrogen fossil fuels. Fuel Process. Technol. 71,71-78. 

Crowther, J., Fr.B. Lo, M.W. Rawlings, and B. Wright. 1995. Determination of organically bound sulfur in swamp and terrestrial waters by continuous flow oxidation and ion chromatography. Environ. Sci. Technol. 29 849-855. 

Several papers in this book and in the recent literature (3) discuss use of pyrolysis techniques coupled with gas chromatography and mass spectrometry to determine forms of organically bound sulfur, but these methods introduce an uncertainty due to the possible interconversion of these sulfur forms during the heating step. For example, it has been shown that when benzyl sulfide was heated to 290°C, tetraphenyl thiophene, hydrogen sulfide and stilbene were produced (4). Coupled with heat and mass transport limitation considerations, particularly for viscous liquids and solids, it is not unreasonable to question whether at least some of the thiophenic forms observed by these techniques were produced during the analysis and may not have been present in the original sample. 

Although a detailed analysis of the XANES spectra in Figure 1 is outside the scope of this paper, it is apparent that the spectra can readily be used as a fingerprint for the electronic nature of organically bound sulfur. 

Characterization of Organically Bound Sulfur in High-Molecular-Weight, Sedimentary Organic Matter Using Flash Pyrolysis and Raney Ni Desulfurization... 

SINNINGHE DAMSTE ET AL. Organically Bound Sulfur in Organic Matter 487... 

In this paper organically-bound sulfur in three types of high-molecular-weight organic matter (kerogen, asphaltenes and resins) obtained from three organic sulfur-rich sedimentary rock samples has been studied. Kerogen, asphaltene and resin fractions were isolated and characterised by the two described techniques. 

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