Sulfides conversion

By-product processing Hydrogen sulfide Conversion to elemental sulfur or sulfuric acid by liquid absorption, wet oxidation to elemental sulfur, combustion to SO2... 

Could be raised up to 99% at very high sulfide conversions (94%), ratio sulfide HP (1 1). Not determined, conversion of the sulfide 50%. 

The interval between 0.9 and 3.0 equiv. (relative to sulfide substrate) was studied and the general trend showed that the sulfide conversion went up and reached completion at >1.3 equiv. Both sulfoxide content and ee remain relatively stable (much greater than 90%) and it is only at the highest peroxide levels (>2 equiv.) when the former falls off due to a considerable sulfone formation (14—19%) (see Fig. 10). This tendency was strengthened when reaction times were prolonged, and so on leaving the mixture with 14% sulfone overnight the content had increased to over 42%. 

To study the influence of the nature of the solvent, the oxidation of ethyl sulfide was carried out at 303 K in the presence of methanol (MeOH), ethanol (EtOH), tert-butanol (t-BuOH), acetonitrile (MeCN), acetone (Me2CO) or tetrahydrofiiran (ITIF) as solvents. Figure 3 shows the sulfide conversion for a reaction time of 60 min, both over Ti-containing zeolites and without catalyst. 

A good selectivity in sulfoxide is obtained at a 80% conversion of sulfides under all conditions. This selectivity depends on the sulfide and solvent nature, or the molar ratio H2O2 / thioether, and is directly linked to the reactivity high sulfide conversions for a short reaction time lead to high selectivities in sulfoxides. 

B. Gas purification (removal of water, dust, and hydrogen sulfide, conversion of organic sulfur in the presence of highly alkalized iron catalysts). 

The conversion of serine to cysteine involves some interesting reactions. The source of the sulfur in animals differs from that in plants and bacteria. In plants and bacteria, serine is acetylated to form O-acetylserine. This reaction is catalyzed by serine acyltransferase, with acetyl-GoA as the acyl donor (Figure 23.13). Conversion of O-acetylserine to cysteine requires production of sulfide by a sulfur donor. The sulfur donor for plants and bacteria is 3 -phospho-5 -adenylyl sulfate. The sulfate group is reduced first to sulfite and then to sulfide (Figure 23.14). The sulfide, in the conjugate acid form HS", displaces the acetyl group of the O-acetylserine to produce cysteine. Animals form cysteine from serine by a different pathway because they do not have the enzymes to carry out the sulfate-to-sulfide conversion that we have just seen. The reaction sequence in animals involves the amino acid methionine. 

Hydrogen sulfide conversions of up to 62 mL min i were obtained at 900 °C with a 40% H2S stream flowing at 200 mL mimL This corresponded to an equivalent current density of 710 mA cm and close to 550% removal beyond that expected from thermodynamic hydrogen sulfide thermal decomposition at this... 

Kahna DW, Mass ET Jr (1985) Indirect hydrogen sulfide conversion-I. An acidic electrochemical process. Int J Hydrogen Energy 10(3) 157-162... 

Substrates oxidized are thioanisole, diphenyl sulfide, tetrahydro-thiophene, pentamethylene sulfide. Conversion of thioether is greater than 90 %, with 95 % or better selectivities to the sulfoxide. The kinetics of the catalytic reaction is consistent with the following mechanism ... 

A larger scale application of an alcohol into sulfide conversion was... 

Oxygen, nitrate, and nitrite profiies in a thick biofiim from a wastewater treatment plant (a) and local conversion rates calculated from these profiles (b). In (c) also the total sulfide conversion rates are plotted (sulfide profiles not shown), demonstrating that sulfide production occurs in the deep biofilm (ca. 1-mm depth] and sulfide oxidation overlaps with the denitrifying zone... 

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