Oxidation of elemental sulfur

The products of the direct oxidation of elemental sulfur in air or oxygen were examined early in this century. In this review we will refer only to those papers which provide some information on rates or mechanisms of the reactions. 

Bodenstein and Karo in 1911 studied the oxidation of sulfur at 252 C and believed the overall reaction to be 

They found the reaction to be first order in O2 and that the rate was proportional to the surface of the sulfur, with a temperature coefficient of 1.87 (i.e., an activation energy of 34.6 kcal.mole ). They found the rate to be unaffected by the SO2 formed. They concluded that the reaction takes place between the liquid sulfur and adsorbed oxygen. 

Emeleus showed that the luminous oxidation which occurred at temperatures below the ignition point was sensitive to the presence, not only of SO2, but also other gases. These species acted to inhibit the reaction. The products of reaction consisted mostly of SO2 and about 2 % SO3. 

Semenov and Rjabinin studied the oxidation of sulfur in a vessel containing solid sulfur at temperatures of 80-120 with O2 present at pressures under 20 torr. They found SO2 and SO3 as products, with the SO3 varying from 20 to 60 % of the total products. As in the case of phosphorus oxidation, the total pressure fell asymptotically to a minimum as the sulfur was oxidized. There was also a short induction period, the duration of which was temperature-dependent. Above a certain maximum and below a minimum value of sulfur pressure the oxidation was immeasurably slow. They concluded that either ozone or active S atoms initiated chain reactions by inducing the formation of chain carriers. Semenov and Rjabinin generally found no reaction between sulfur vapor and oxygen at 80-120° unless initiated by a pulsed electrical discharge. This reaction was accompanied by a luminescence, and its rate was almost independent of [O2] when this was below 1 torr, until the [O2] fell to about 0.2 torr, when the reaction ceased. The emission filled the vessel unless [O2] exceeded 20 torr, in which case it was confined to the surface of the sulfur. 

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Suzuki 1.1965a. Oxidation of elemental sulfur by an enzyme system from Thiobacil-lus thiooxidans. Biochlm Biophys Acta 104 395-71. 

A few mechanisms were postulated for this reaction (6). No matter what mechanism is considered, the oxidation of elemental sulfur or thiosulfate is accompanied by reductive cleavage of the sulfur-sulfur bridges. In the case of sulfur, the intermediate involved is a cyclic form of sulfur, probably Ss, although there is little difference observed for different allotrophic forms of sulfur such as rhombic, precipitated, and amphorous. These cyclic sulfides form the basis of polysulfanes and polythionates which could be metabolized readily by Thiobacilli (as shown in Figure 3). Actually, sulfur oxidation begins with its reduction, in which the gluathione-sulfhydryl groups located near the cell surface take part ... 

Other Thiobacillus produce sulfate from the oxidation of elemental sulfur and other inorganic sulfur compounds ... 

Oxidation of elemental sulfur and selenium with SbFs leads to the formation of doubly charged polyatomic cations [26]. These cations can react with polyfluorinated arenes to form diaryl sulfides or selenides (Eq. 12) [27]. 

Silver, M., 1970. Oxidation of elemental sulfur and sulfur compounds and CO2 fixation of Ferrobacillus ferrooxidans. Can. J. Microbiol., 16 845—870. 

The most interesting examples of microbial oxidation of elemental sulfur... 

Yagi, S., Kitai, S. and Kimura, T., 1971. Oxidation of elemental sulfur to thiosulfate by Streptomyces. Appl. Microbiol., 22 157—159. 

Hydrogen sulfide can be oxidised to elemental sulfur, for example, by green and purple sulfur bacteria. Further oxidation of elemental sulfur by sulfur oxidising bacteria can produce sulfate. 

Sulfur Dioxide to Sulfur Trioxide Process. The manufacture of sulfuric acid involves the oxidation of elemental sulfur to SO2, followed by the catalytic oxidation of SO2 to SO3 over vanadium pentoxide. The next step involves the absorption of SO3 with water to form H2SO4. The SO2 oxidation reaction to... 

Acidithiobacillus ferrooxidans anaerobically oxidizes elemental sulfur and formate with ferric ion (Sugio et al., 1985 Pronk et al., 1991a Das et al., 1992). The bacterial oxidation of elemental sulfur and formate with ferric ion is inhibited by HOQNO but not by azide. In the oxidation of elemental sulfur with ferric ion free energy of 75 kcal/S° is liberated, which is enough to support the growth of the bacterium. Thus, the bacterium grows anaerobically by oxidizing elemental sulfur with ferric ion (Pronk et al., 1992). 

Suzuki I, Chan CW, Takeuchi TL (1992) Oxidation of elemental sulfur to sulfite by Thiobacillus thiooxidans cells. Appl Environ Microbiol 58 3767-3769 Suzuki I, Dular U, Kwok S-C (1974) Ammonia or ammonium ion as substrate for oxidation by Nitrosomonas europaea cells and extracts. J Bacteriol 120 556-558 Suzuki I, Kwok S-C (1970) Cell-free ammonia oxidation by Nitrosomonas europaea effects of polyamines, Mg2+ and albumin. Biochem Biophys Res Commun 39 950-955 Suzuki I, Kwok S-C (1981) A potential resolution and reconstitution of the ammonia oxidizing system of Nitrosomonas europaea. Role of cytochrome c-554. Can J Biochem 59 484-488... 

The preparation and properties of homopolyatomic cations of the Group VI elements have been reviewed recently.1 The general method described below, involving the oxidation of elemental sulfur, selenium, and tellurium with either antimony pentafluoride or arsenic pentafluoride in liquid sulfur dioxide, is convenient for the preparation of compounds containing these polyatomic cations. The procedure is basically that briefly described previously2 for the preparation of Se8(Sb2F j i )2. 

Oxidation of elemental sulfur to sulfate results in the prodnction of hydrogen ions that can lower pH. Thiobaccillus species such as T. thiooxidans grow well under acidic soil conditions, oxidizing sulfur to sulfate under aerobic conditions ... 

Suzuki, I. Oxidation of Elemental Sulfur by an Enzyme System of ThiobacUlus thiooxidans. Biochim. Biophys. Acta 104, 359 (1965). 

I) (sequential) oxidation of elemental sulfur in excess of oxygen ... 

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