Forms of organic sulfur

FCC feedstocks contain sulfur in the form of organic-sulfur compounds such as mercaptan, sulfide, and thiophenes. Frequently, as the residue content of crude oil increases, so does the sulfur content (Table 2-5). Total sulfur in FCC feed is determined by the wavelength dispersive x-ray fluorescence spectrometry method (ASTM D-2622), The results are expressed as elemental sulfur. 

The second form of organic sulfur is released at temperatures... 

Dimethylsulfoniopropionate (DMSP) is an organic sulfur compound that occurs at high concentrations in many marine algae and plants, wnere it fulfills an osmotic function (1.21. DMSP is a principal form of organic sulfur in productive marine environments and its microbial catabolism entails either enzymatic cleavage to dimethyl sulfide (DMS) and aciylate (3.41 ... 

Kavcics results on the forms of organic sulfur were confirmed by Ignasiak et al. (7), who determined that about one third of the sulfur in Rasa coal is in thioether links. This result was determined using two independent techniques. Ignasiak et al. also concluded that mercaptanic sulfur was absent from Rasa coal because unspecified chemical tests failed to reveal its presence. 

A breakdown of processes causing the release of S02 from anthropogenic sources is shown in Table 10-8. The combustion of coal now contributes 60% to all such emissions, that of petroleum and its products 28%, and the smelting of nonferrous ores as well as miscellaneous industrial processes take up the remainder. Individual emission estimates are derived as usual by combining statistical production data with emission factors. Fossil fuels contain sulfur primarily in the form of organic sulfur compounds. Combustion turns them into S02, which is vented with the flue gases. The ashes retain very little sulfur, so that emission factors for coals correspond closely... 

Glutathione is the major form of organic sulfur in the soluble fraction of plants grown under sulfur-sufficient conditions. The literature pertaining to the... 

Although no conclusive evidence has been reported so far, the possible importance of organic sulfur species as sulfate aerosol precursors is supported by several observations. Sulfuric acids, sulfonic acids, and other organic sulfur compounds are formed in sulfur dioxide-hydrocarbon reactions at high concentrations. Organosulfiir radical species, such as RSO2 and RO2SO2 have been postulated as intermediates for these reactions. Suzuki (see Penzhom et o/. ) observed polymer formation from... 

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). 

As discussed in Chapter 2 and in more detail in Chapter 11, a variety of organic sulfur compounds in addition to inorganics such as H2S and COS are emitted by biological sources. In the troposphere, they may ultimately be oxidized to S02 and H2S04. However, the chemistry of these compounds tends to be complex, and a variety of partially oxidized sulfur compounds is formed first. 

Photoreactions are often complex reactions that not only control the fate of many chemicals in air and water, but often produce products with chemical, physical, and biological properties quite different from those of their parent compounds more water soluble, less volatile, and less likely to be taken up by biota. Photooxidation removes many potentially harmful chemicals from the environment, although occasionally more toxic products form in oil slicks and from pesticides (Larson et al., 1977). Biogeochemical cycling of organic sulfur compounds in marine systems involves photooxidation on a grand scale in surface waters, as well as in the troposphere (Brimblecombe and Shooter, 1986). 

Mineralization of organic sulfur to the inorganic form, hydrogen sulfide (H2S). 

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