Oxidizing capacity

An oxirane process utilizes ethylbenzene to make the hydroperoxide, which then is used to make propylene oxide [75-56-9]. The hydroperoxide-producing reaction is similar to the first step of cumene LPO except that it is slower (2,224,316—318). In the epoxidation step, a-phenylethyl alcohol [98-85-1] is the coproduct. It is dehydrated to styrene [100-42-5]. The reported 1992 capacity for styrene by this route was 0.59 X 10 t/yr (319). The corresponding propylene oxide capacity is ca 0.33 x 10 t/yr. The total propylene oxide capacity based on hydroperoxide oxidation of propylene [115-07-1] (coproducts are /-butyl alcohol and styrene) is 1.05 x 10 t/yr (225). 

Propyleae oxide is produced by oae of two commercial processes the chlorohydrin process or the hydroperoxide process. The 1995 global propyleae oxide capacity was estimated at about 4.36 x 10 t/yr. About half came from each of the two processes. Table 3 summari2es the global productioa capacities for each of the processes. 

The most important chemical reaction of chi orohydrin s is dehydrochloriaation to produce epoxides. In the case of propylene oxide. The Dow Chemical Company is the only manufacturer ia the United States that still uses the chlorohydrin technology. In 1990 the U.S. propylene oxide production capacity was hsted as 1.43 x 10 t/yr, shared almost equally by Dow and Arco Chemical Co., which uses a process based on hydroperoxide iatermediates (69,70). More recentiy, Dow Europe SA, aimounced a decision to expand its propylene oxide capacity by 160,000 metric tons per year at the Stade, Germany site. This represents about a 40% iacrease over the current capacity (71). 

There are 12 producers of ethylene oxide ia the United States. Table 9 shows the plant locations, estimated capacities, and types of processes employed. The total U.S. production capacity for 1992 was ca 3.4 x 10 metric tons. The percentages of total domestic production made by the air- and oxygen-based processes are ca 20 and 80%, respectively. The largest producer is Union Carbide Corp. with approximately one-third of the United States ethylene oxide capacity. About 94% of domestic ethylene oxide capacity is located on the Gulf Coast near secure and plentiful ethylene suppHes. Plans for additional U.S. production ia the 1990s have been announced by Union Carbide (incremental expansions), Eormosa Plastics (at Pt. Comfort, Texas), and Shell (at Geismar, Louisiana) (101). 

United States production of ethylene oxide in 1990 was 2.86 x 10 metric tons. Approximately 16% of the United States ethylene (qv) production is consumed in ethylene oxidation, making ethylene oxide the second largest derivative of ethylene, surpassed only by polyethylene (see Olefin polymers). World ethylene oxide capacity is estimated by country in Table 11. Total world capacity in 1992 was ca 9.6 x 10 metric tons. 

Pits often occur beneath adhering substances where the oxidizing capacity is not replenished sufficiently within the pores or cavities to maintain passivity there. Once the pit is activated, the surface surrounding the point becomes cathodic and penetration within the pore is rapid. 

Biopsy findings show disseminated muscle fiber atrophy which is confined to type 2 fibers, in many instances with type 2B (glycolytic) fibers most affected (Figure 23). Muscle necrosis is not seen, though at ultrastructural level focal myofibrillar disruption and myofilament loss may be evident. The muscle atrophy seems to be due to decreased protein synthesis, and at high doses, to increased catabolism. The reason for the selective effect on phasic, glycolytic fibers is not clear since, although steroids interfere with carbohydrate metabolism and oxidative capacity, there seems to be no overall effect on ATP levels. Nevertheless it has been... 

The discussion above refers to the classical dark conditions where the chemical activation is achieved thermally. Fenton requires a moderate thermal activation, resulting in a reaction temperature ranging from 25 to 90 °C. The oxidizing capacity of the Fenton reaction can be increased by UV or UV-vis Hght irradiation [160, 161]. The increase is interpreted by means of the photoreduction ability of Fe ... 

Recent reports describe more sophisticated detemplation methods. However, they are limited to mesoporous materials for the reasons described before. We show how Fenton chemistry can fulfill various missing challenges (i) it provides a powerful oxidation capacity at low(er) temperatures and (ii) it can work for microporous compounds as well. 

On the other hand, Kolthoff et established that the ratio [Fe(II)] reacted/ [S2O8 ] reacted in acidic, neutral and alkaline medium is the same but much less than 2, if iron([f) is added at very low speed. The decrease in the oxidizing capacity can be explained by the induced decomposition of peroxydisulphate, though the detection of oxygen as a product was not successful. 

Taken pH 0.1 N KSCN (ml) Time of reaction (sec) Total oxidizing capacity ... 

Videla, L., Bernstein, J. and Israel, Y. (1973). Metabolic alterations produced in the liver by chronic ethanol administration, increased oxidative capacity. Biochem J. 134, 507-515. 

The model inadequacy was particularly evident for the systems having different Ba loadings, which showed an increase in the breakthrough time associated with similar NO oxidizing capacity. Work is currently in progress in order to gain a better adequacy of the model to our data in particular the nitrite route has also been included to provide an additional NO adsorption pathway, which is in line with obtained data, and preliminary results obtained in this direction seem to be promising. 

Sung, H.J., Feitz, A.J., Sedlak, D.L. and Waite, T.D. (2005) Quantification of the oxidizing capacity of nanoparticulate zero-valent iron. Environmental Science and Technology, 39, 1263—1268. 

MnP is the most commonly widespread of the class II peroxidases [72, 73], It catalyzes a PLC -dependent oxidation of Mn2+ to Mn3+. The catalytic cycle is initiated by binding of H2O2 or an organic peroxide to the native ferric enzyme and formation of an iron-peroxide complex the Mn3+ ions finally produced after subsequent electron transfers are stabilized via chelation with organic acids like oxalate, malonate, malate, tartrate or lactate [74], The chelates of Mn3+ with carboxylic acids cause one-electron oxidation of various substrates thus, chelates and carboxylic acids can react with each other to form alkyl radicals, which after several reactions result in the production of other radicals. These final radicals are the source of autocataly tic ally produced peroxides and are used by MnP in the absence of H2O2. The versatile oxidative capacity of MnP is apparently due to the chelated Mn3+ ions, which act as diffusible redox-mediator and attacking, non-specifically, phenolic compounds such as biopolymers, milled wood, humic substances and several xenobiotics [72, 75, 76]. 

Levels of glutathione, as a measure of anti-oxidant capacity, were shown to be higher in strawberry plants grown in compost than in plants grown with... 

Each bead can iodinate up to 500 pg of tyrosine-containing protein or peptide. This translates into an oxidative capacity of about 0.55 pmol per bead. The rate of reaction can be controlled by changing the number of beads that are used and altering the sodium iodide concentration added to the reaction. Reaction volumes of 100-1,000 pi are possible per bead. The following protocol is suggested for iodinating proteins. Optimization should be done to determine the best incorporation level to obtain good radiolabel incorporation with retention of protein activity. 

The mechanism of tellurium resistance has been investigated using genetic manipulation similar to that of Se (see above) and cellular oxidant capacity apparently plays an important role.144,206 A few tellurite determinants - both chromosomal and plasmid encoded - have been identified in bacte-ria.113,147 192 207 208 Recent studies have focused on the role of methyltransf-erases in Te resistance. Liu et a/.111 determined that the E. coli gene tehB uses S-adenosyl methionine and a methyltransferase in tellurite detoxification, but while no methylated tellurium compounds (see below) were observed, a loss of tellurite was observed in tellurite-amended cultures and Te complexation was inferred.191... 

Prior to the Seattle Workshop, several batches of seawater from Hawaii were distributed to attendees for analysis. It became immediately clear to workshop participants that the key to making valid comparisons was both a common reference material and a uniform blank solution (Hedges et al., 1993 Sharp, 1993). The primary source of discrepancy among analysts was poor blank control, not oxidative capacity. 

Conversely, when the host structure has a strong oxidizing capacity, such as xerogel V2O5, the in situ polymerization is concomitant with the in-... 

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