Oxidative desulfuration

Oxidative Desulfurization Process. Oxidative desulfurization of finely ground coal, originally developed by The Chemical Constmction Co. (27,28), is achieved by converting the sulfur to a water-soluble form with air oxidation at 150—220°C under 1.5—10.3 MPa (220—1500 psi) pressure. More than 95% of the pyritic sulfur and up to 40% of the organic sulfur can be removed by this process. 

Oxidative desulfuration releases active sulfur that binds to, and deactivates, P450 Selective inhibitors Specific inhibitor of lAl Specific inhibitor of 1A2 Specific inhibitor of 2A6 Specific inhibitor of 2C9 Specific inhibitor of 2D1 Specific inhibitor of 2E1... 

This process of aging is believed to be critical in the development of delayed neuropathy, after NTE has been phosphorylated by an OP (see Chapter 10, Section 10.2.4). It is believed that most, if not all, of the B-esterases are sensitive to inhibition by OPs because they, too, have reactive serine at their active sites. It is important to emphasize that the interaction shown in Fignre 2.11 occurs with OPs that contain an oxon group. Phosphorothionates, which contain instead a thion group, do not readily interact in this way. Many OP insecticides are phosphorothionates, but these need to be converted to phosphate (oxon) forms by oxidative desulfuration before inhibition of acetylcholinesterase can proceed to any significant extent (see Section 2.3.2.2). 

Desulfurization processes are absolutely necessary for producing clean fuels. Possible strategies to realize ultradeep suffiirization currently include adsorption, extraction, oxidation, and bioprocesses. Oxidative desulfurization (ODS) combined with extraction is considered one of the most promising of these processes [13]. Ultradeep desulfurization of diesel by selective oxidation with amphiphilic catalyst assembled in emulsion droplets has given results where the sulfur level of desulfurized diesel can be lowered from 500 ppm to about 0.1 ppm without changing the properties of the diesel [12]. 

Data presentations should include the parent compound and all toxic transformation products. This is particularly important for oxidation of sulfide linkages to sulfoxides or sulfones. These products are often equally toxic to the parent with increased availability. Attention should also be given to oxidative desulfuration of phosphorothionate esters. 

The second type of biological process is a direct treatment process, in which bacteria oxidize the sulfur species. This oxidative desulfurization reaction is carried out in the presence of an electron acceptor (such as nitrate, NOs ), a source of carbon (such as carbon dioxide or I ICO, ), and a source of reduced nitrogen (such as ammonia). The... 

Method for oxidation of organic sulfur compound included in organic compound and method for oxidative desulfurization of fuel oil [104],... 

Kurane, R. Miki, K. Ukekawa, K., and Yamamoto, J., Method for oxidation of organic sulfur compound included in organic compound and method for oxidative desulfurization of fuel oil. Patent No. JP2001151748. 2001, June 05. 

Oxidative desulfurization of sulfur compounds Oxidation of thiophene and derivatives with hydrogen peroxide using Ti-Beta catalyst... 

Organic sulfur compounds are present in gasoline and diesel. With the increased emphasis on the requirement for more environmentally friendly transportation fuels [1], oxidative desulfurization, using H202 and redox-molecular sieves [2,5,6,7], has been studied and shown to significantly reduce the sulfur content of gasoline and diesel. The reaction of thiophene and its derivatives were successfully converted to oxidized compounds, but the identification of oxidized compounds was not simple because the concentrations of individual sulfur compounds were low. Most of the previous literature has reported sulfone formation. 

Fish rapidly absorb, metabolize, and excrete chlorpyrifos from the diet (Barron etal. 1991). The mechanism of action of chlorpyrifos occurs via phosphorylation of the active site of acetylcholinesterase after initial formation of chlorpyrifos oxon by oxidative desulfuration. In studies with channel catfish (Ictalurus punctatus), the oral bioavailability of chlorpyrifos was 41%, substantially higher than in mammals. Catfish muscle contained less than 5% of the oral dose with an... 

Aryl and alkyl hydroxylations, epoxide formation, oxidative dealkylation of heteroatoms, reduction, dehalogenation, desulfuration, deamination, aryl N-oxygenation, oxidation of sulfur Oxidation of nucleophilic nitrogen and sulfur, oxidative desulfurization Oxidation of aromatic hydrocarbons, phenols, amines, and sulfides oxidative dealkylation, reduction of N-oxides Alcohol oxidation reduction of ketones Oxidative deamination... 

Extractive Oxidative Desulfurization of fuels with Hydrogen Peroxide in presence of catalysts... 

GHG) emission). Hence, alternative methods are gaining importance among which oxidative desulfurization (ODS) has attracted worldwide attention due to inherent advantages like mild reaction conditions and low cost. 

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. 

Thus, although organophosphorus compounds like fenitrothion may be metabolized in aquatic organisms through oxidative desulfuration, side chain oxidation, hydrolytic cleavage of P-O-arryl linkage, as well as O-demethylation, the turn-over rate apparently is much lower than in mammals. 

Insecticides of the phosphoric acid triester class include paraoxon (9.49) and dichlorvos (9.50). The phosphorothioate derivative parathion is a relatively non-toxic insecticide that undergoes monooxygenase-catalyzed oxidative desulfuration to paraoxon [105] (see also Chapt. 7 in [59] see Sect. 9.3.6). Paraoxon itself, like its congeners and the P-halide nerve gases, is highly toxic through its potent inactivation of acetylcholinesterase [69]. 

Phosphorothioates and phosphonothioates are of particular significance as insecticides. Schematically, it can be stated that these xenobiotics undergo activation by oxidative desulfuration, and detoxification by hydrolytic cleavage. Oxidative desulfuration transforms phosphorothioates and phosphonothioates to the corresponding oxon derivatives (see Chapt. 7 in [59]), which are highly toxic as potent inactivators of acetylcholinesterase [69]. This route of toxification can be competitive with and/or followed by cleavage reactions, which can be either hydrolytic or oxidative. 

The formal mechanism of oxidative desulfuration has been discussed in detail in an earlier book (Chapt. 7 in [59]). As shown in schematic and simplified form in Fig. 9.12, monooxygenase-catalyzed 5-oxygenation of phosphorothioates (9.67, X = O) and phosphorodithioates (9.67, X = S) yields an... 

In the case of malathion (9.74), oxidative desulfuration is again a very minor route in mammals, but for another reason. Here indeed, the two car-boxylate functions make the compound such a good substrate of carboxyles-... 

Organic isothiocyanates (R-N=C=S) found in dietary sources or used therapeutically. In this case, the formation of isocyanate occurs by oxidative desulfuration (Chapt. 7 in [50]). 

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