Oxidation of Sulfur Compounds

Similarly, SO2 and SO3 (SOJ compounds are produced in combustion by the oxidation of sulfur compounds within the fuel source. SO , emitted into the atmosphere can be incorporated into aerosol particles and wet-deposited as corrosive sulfuric acid. Both NO , and SO , emissions contribute to acid rain content from wet deposition, due to their participation in the formation of nitric and sulfuric acid, respectively. 

As a safer alternative to digestion of vegetable matter with perchloric acid, alkaline oxidation of sulfur compounds to sulfate by sodium hypobromite, and reduction of sulfate to hydrogen sulfide by hydriodic acid/formaldehyde/phosphinic acid is recommended. 

We, at IIP carried out certain oxidation studies and report the results on oxidation of sulfur compounds present in gas oil using carboxylic acid / H2O2 system. Extent of sulfur removal in gas oil after oxidative desulfurization was monitored by sulfur analysis. Oxidation and solvent extraction reduced sulfur in gas oil from 1.5% to 0.20% in single stage batch extractor. 

Thermal oxidation of sulfur compounds to S02, followed by catalytic oxidation to SO. Absorption of SO3 by concentrated sulfuric acid creates net prcduct acid... 

A unique feature of the oxidation of pure sulfur is that the percentage of S03 formed is a very much larger (about 20%) fraction of the SOx than is generally found in the oxidation of sulfur compounds. 

Some microorganisms can catalyze certain oxido-reduction reactions like the oxidation of iron and manganese in water, the oxidation of sulfur compounds, and oxidation-reduction of nitrogen compounds. Aerobic autotrophic bacteria of the type Thiobacillus can release soluble iron, copper, and sulfuric acid as sulphates into water. These organisms can be found everywhere in nature wherever an acidic environment is maintained in the presence of sulfide-containing minerals. 

A range of metal catalysts can be employed with peroxygen species for the effective oxidation of sulfur compounds. For example, branched-chain high molecular weight mercaptans are difficult to oxidize with hydrogen peroxide. However, this difficulty is overcome if the reaction is conducted with hydrogen peroxide in the presence of a copper(II) salt.395 The formation of a copper(I) mercaptide followed by its oxidation are believed to be the key steps. 

Sometimes the natural oxidation of sulfur compounds exposed to air and rainwater will generate sulfuric acid that may lower the pH to extremely acidic values. This is typical of mine spoilage or acid mine drainage, AMD, where pyrite (FeS2) is exposed to oxidation ... 

MILD AND SELECTIVE OXIDATION OF SULFUR COMPOUNDS IN TRIFLUOROETHANOL DIPHENYL DISULFIDE AND METHYL PHENYL SULFOXIDE... 

The evolution of photosynthetic oxidation of sulfur compounds permitted the development of the full microbial sulfur cycle in sulfureta. In this cycle, some bacteria and archaea reduce oxidized sulfur compounds, pumping them downward in the microbial mat, while other bacteria reoxidize them photosynthetically. The development of this cycle, coupled with the use of stored sulfur as a redox bank balance that could be exploited either way the redox budget swung during tidal and diurnal cycles, would have greatly expanded the thermodynamic power of the biosphere. 

D. The Mechanisms of Oxidation of Substrates 1. The Oxidation of Sulfur Compounds... 

Isotope selectivity during oxidation of sulfur compounds... 

A sulfur center in oligomeric or polymeric elemental sulfur as well as in sulfur compounds (especially those with catenated sulfur chains) can be attacked by electrophiles and nucleophiles. By far the most important electrophilic attack is the reaction of sulfur with oxygen (also the oxidation of sulfur compounds with oxidation states below -1-6, e.g., H2S or SO2). Despite the complicated and not fully understood mechanism as well as the economic importance (formation of H2SO4), those reactions of sulfur with oxygen are beyond the scope of this section. 

Oxidation of sulfur compounds. Xanthates are converted to sulfines, and i-butylsulfmamides to sulfonamides. Thus, amines can be protected via sulfmylation, and the sulfonamides are cleaved by TFA or TfOH. Thiophene oxides are obtained when thiophenes are treated with MCPBA-BFj OEtj. ... 

Oxidation of sulfur compounds. The copper(lI) nitrate complexed with dimerizes thiols to afford disulfides and oxidizes sulfides to sulfoxides. 

A remarkable effect of the reaction medium has been observed in the heterogeneously catalyzed diastereoselective oxidation of sulfur compounds as shown in Scheme 14 [82]. The reaction, which was completely non-selective in conventional solvents, could be optimized up to 95% de in SCCO2 whereby a dramatic dependence on pressure (and hence bulk density) was observed. Although no fully satisfactory explanation is yet available for these results, they seem to support again the potential to use the density of SCCO2 as an additional parameter for the optimization of organic syntheses. 

The oxidation of sulfur compounds in the sulfur-oxidizing bacteria is performed by the combination of several elemental reaction processes, and each of the processes is performed by a cooperation of several enzymes and cytochromes. The elemental reaction processes included in the bacterial oxidation of sulfur compounds will be described in the following section. 

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