Sulfur compounds transformation

The largest investment has been in desulfurization, and in most instances it has been proven that the sulfur compounds have been transformed into oxidized moieties, but the actual cleavage of the last C—S bond in most cases does not take place to the extent desired or to levels needed for implementing BDS. Other processes such as demetallization and upgrading are just starting to be studied. Collateral technologies, for gas treatment and reducing viscosity by emulsification ( in well treatments) are commercially available. 

Gonzalez JM, Kiene RP, Moran MA (1999) Transformation of sulfur compounds by an abundant lineage of marine bacteria in the a-subclass of the Proteobacteria. Appl Environ Microbiol 65 3810-3819... 

In ODS, sulfur compounds present in fuels are oxidized to more polar sulfones / sulfoxides to facilitate their removal by solvent extraction or adsorption. Various oxidation systems have been reported in the literature for this transformation. Among these oxidants like hydrogen peroxide (H2O2) and carboxylic acid as catalyst3"5. For the chemical industry, it becomes more and more important to develop cleaner technologies. Solvent extraction processes are used to separate sulfones / sulfoxides from oxidized fuels. These processes required suitable and selective solvents for separation of oxidized sulfur compounds from petroleum feedstocks. 

Chemical/Physical. At room temperature, concentrated sulfuric acid will react with pyrene to form a mixture of disulfonic acids. In addition, an atmosphere containing 10% sulfur dioxide transformed pyrene into many sulfur compounds, including pyrene-1-sulfonic acid and pyrenedisulfonic acid (Nielsen et al., 1983). 

Yang and Zhu [107] have studied, applying several electrochemical methods and mercury electrodes, electrochemical behavior of pharmaceutically important dipeptide captopril. In acidic solution, one-electron transfer led to the formation of a univalent mercury-sulfur compound, which was strongly adsorbed at the electrode surface and gradually transformed into the divalent mercury-sulfur compound. 

Products of the LOX pathway or compounds formed by autoxidation of fatty acids (Scheme 7.2) are also important for leek aroma [31, 163]. Volatile compounds of the LOX pathway are not pronounced in the aroma profile of freshly cut leeks owing to a high content of thiosulfinates and thiopropanal-S-oxide [30]. In processed leeks that have been stored for a long time (frozen storage), however, these aliphatic aldehydes and alcohols have a greater impact on the aroma profile owing to volatilisation and transformations of sulfur compounds [31, 165]. The most important volatiles produced from fatty acids and perceived by GC-O of raw or cooked leeks are pentanal, hexanal, decanal and l-octen-3-ol (Table 7.5) [31, 35, 148, 163, 164]. 

In seeking new and improved ways for achieving the ultralow levels of sulfur in the fuels of the future, it is important to understand the nature of the sulfur compounds that are to be converted (especially PASCs), as described in Section III. It is equally important to understand how these transformations occur through interactions with catalytic surface species, the pathways involved during these transformations, and the associated kinetic and thermodynamic limitations. These considerations dictate the process conditions and reactor process configurations that must be used to promote such transformations. In this section, we describe the reactor configurations and process conditions being used today what is known about the catalyst compositions, structure, and chemistry and what is known about the chemistry and reaction pathways for conversion of PASCs in conventional HDS processes. 

The Corey Kim procedure is the oxidation method of choice for the transformation of (3-hydroxycarbonyl compounds into 1,3-dicarbonyl compounds. Treatment of (3-hydroxycarbonyl compounds under Corey Kim conditions leads to an intermediate 1,3-dicarbonyl compound 33 that reacts in situ with activated DMSO, resulting in the generation of a stable sulfur ylide 34. This sulfur compound can be transformed into the desired 1,3-dicarbonyl compound by reduction with zinc in acetic acid.254... 

Jokic, A., Cutler, J. N., Ponomarenko, E., van der Kamp, G., and Anderson, D. W. (2003). Organic carbon and sulfur compounds in wetland soils Insights on structure and transformation processes using K-edge XANES and NMR spectroscopy. Geochim. Cosmo-chim. Acta. 67, 2585-2597. 

Methionine as a Precursor of DMS. Methionine was recognized as a precursor of methylated sulfur compounds about 50 years ago (see 12 for references). Subsequent studies have shown the production of volatile methylated sulfides from methionine in many environments. The emphasis has been on anaerobic transformation in studies with natural samples or microcosms. Francis et al. (181 observed the production of methanethiol, DMS and DMDS from methionine in soil incubations. The production of the volatile sulfur... 

One means to assess the relative contributions of the various sources of sulfur to the atmosphere is through the use of sulfur isotope ratios (12-16). Isotopic ratios may be used as source tracers if 1) the isotopic composition of the sources as they enter the atmosphere are known, 2) the isotopic compositions of the various sources are different from one another, and 3) the isotopic changes that occur during biological, physical and/or chemical transformations are understood. Presently, isotopic data for sulfur compounds in the remote atmosphere (Table I) are limited. However, collection and analytical techniques are now available to make isotopic measurements of the critical species. In the text that follows, various aspects of sulfur isotope chemistry will be discussed. 

The third, fourth, and fifth sections investigate the distribution and biological and chemical transformations of reduced sulfur compounds in the oceans. The third section focuses primarily on dimethyl sulfide, which is the predominant form of volatile sulfur in the ocean. Research in the past has concentrated on documenting the distribution of DMS in various oceanic environments. The factors controlling this distribution are not well understood. These chapters examine laboratory and field investigations relating DMS production to productivity and spedation. 

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