Sulfur-containing compounds, oxidation

CAAA Clean Air Act amendments of 1990 in the United States, which introduced substantial new controls for nitrogen oxides, sulfur-containing compounds, and, potentially, many metals emissions by power plants. 

Criteria pollutants Pollutants for which federal law governs emissions (nitrogen oxides, sulfur-containing compounds, CO, and particulates are the most significant criteria pollutants for coal-based power systems). 

The catalysts are prepared by impregnating the support with aqueous salts of molybdenum and the promoter. In acidic solutions, molybdate ions are present largely in the form of heptamers, [Mo2024] , and the resulting surface species are beHeved to be present in islands, perhaps containing only seven Mo ions (100). Before use, the catalyst is treated with H2 and some sulfur-containing compounds, and the surface oxides are converted into the sulfides that are the catalyticaHy active species. 

Thiobacillus thiooxidans is an aerobic organism that oxidizes various sulfur-containing compounds to form sulfuric acid. These bacteria are sometimes found near the tops of tubercles (see Chap. 3, Tubercu-lation ). There is a symbiotic relationship between Thiobacillus and sulfate reducers Thiobacillus oxidizes sulfide to sulfate, whereas the sulfate reducers convert sulfide to sulfate. It is unclear to what extent Thiobacillus directly influences corrosion processes inside tubercles. It is more likely that they indirectly increase corrosion by accelerating sulfate-reducer activity deep in the tubercles. 

General Incineration (oxidation) is the best-known method for the removal of gaseous industrial waste. Combustible compounds containing carbon, hydrogen, and oxygen are converted to carbon dioxide and water by the overall exothermic reactions [Eq. (13.72)]. When chlorinated or sulfur-containing compounds are present in the effluent, the products of combustion include HCl/CE or S02/S03. ... 

Iliev, V., Ileva, A. and Bilyarska, L. (1997). Oxidation and photooxidation of sulfur-containing compounds in the resence of immobilized phthalocyanine complexes. J. Mol. Catal. A Chem. 126, 99-108... 

The catalytic activities of Ti-MMM, Ti-SBA-15, and TS-1 are compared in Table XXXIII (234). The activities of these titanoslicates for MPS oxidation are in the order Ti-MMM > Ti-SBA-15 > TS-1. The catalytic activity was found to correlate with the rate of H202 decomposition in the absence of the organic reactant (Fig. 39). Ti-MMM on which H202 decomposed (to H20 and 02) faster (curve b) was also more active in the oxidation of the sulfur-containing compounds (Table XXXIII). 

An efficient, low temperature oxidation catalyst was developed based on highly disperse metal catalyst on nanostructured Ti02 support. Addition of dopants inhibits metal sintering and prevents catalyst deactivation. The nanostructured catalyst was formulated to tolerate common poisons found in environments such as halogen- and sulfur-containing compounds. The nanocatalyst is capable of oxidizing carbon monoxide and common VOCs to carbon dioxide and water at near ambient temperatures (25-50 °C). 

One of the main research interests in this area is to find new oxidizing agents having the highest chemoselectivity to obtain the sulfoxide derivatives without overoxidation to sulfones. 1,4-Oxathiane 18 was often used as a model sulfur-containing compound to afford 82 (Table 2) and 17 similarly gave 83. m-2,6-Dimethyl-l,4-dithiane was oxidized to the... 

The biosynthesis 237,5381 involves enzymatic dehydration of serine and threonine residues in a manner similar to the formation of thiazoles and dihydrothiazoles vide supra) with or without subsequent oxidation to yield the 2-(l-aminoalkyl)oxazole-4-carboxylic acid and 2-(l-aminoalkyl)dihydrooxazole-4-carboxylic acid shown in Scheme 38. These cyclic peptides display interesting physiological properties such as cytotoxicity/541, 569,5831 antitumor activities, or antineoplastic effects/523,5291 but as for the sulfur-containing compounds the mechanism of action is not yet understood despite extensive SAR studies. 515,521,540,5431... 

Other sulfur-containing compounds Pardo et al. [115] have studied electrochemical oxidation of 2-mercaptopyridine N-oxide on Hg electrodes in aqueous solutions. It has been found that anionic form of this compound was oxidized to yield a radical. At low concentration, oxidation was reversible and the radical was strongly adsorbed. At high concentrations, this process was accompanied by diffusive reversible oxidation. Reorientation of the adsorbed 2-mercaptopyridine N-oxide molecules on Hg electrodes in the presence of Triton X-100 has been studied... 

Organisms such as Thiobacillus thiooxidans and Clostridium species have been linked to accelerated corrosion of mild steel. Aerobic Thiobacillus oxidizes various sulfur-containing compounds such as sulfides to sulfates. This process promotes a symbiotic relationship between Thiobacillus and sulfate-reducing bacteria. Also, Thiobacillus produces sulfuric acid as a metabolic by-product of sulfide oxidation. 

Sulfate shows two peaks, one in the coarse particle mode associated with sea salt, and one in the fine particle mode. The smaller peak is expected since the nss-S04 is formed from the oxidation of S02 and other sulfur-containing compounds such as dimethyl sulfide. The small size of particles containing ammonium reflects the uptake of the gaseous base NH3 into the smaller acidic particles. 

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