Oxidation rates, various organics

Abstract Cataluminescence (CTL) is chemiluminescence emitted in a course of catalytic oxidation. Since 1990, the present authors and coworkers have observed CTL during the catalytic oxidation of various organic vapors in air. This phenomenon has been applied to the CTL-based sensors for detecting combustible vapors. THE CTL response is fast, reproductible and proportional to the concentration of the combustible vapors of ppm orders in air. Based on two types of models of the CTL, the relationship between the CTL intensity and the rate of catalytic oxidation have been investigated analytically. In this article, the effects of catalyst temperature, gas flow-rate and gas concentration on the CTL intensity are demonstrated. Finally, various types of sensing system using the CTL-based sensor are proposed. The results of discrimination and determination of more than ten types of vapors of various concentrations are shown. 

Figure 14. Rates of Oxidation of Various Organics on Lead Ruthenate.

Ferricyanide ion is reduced by e aq in a diffusion-controlled reaction whose rate constant is 3.0 X 109M 1 sec. 1 (27). The oxidation of various organic radicals and radical ions by ferricyanide has been observed directly by pulse radiolysis by Adams et al. (8), Henglein (28), and others [Chambers, K. W., Collinson, E., Dainton, F. S., Seddon, W. A., Wilkinson, F., Trans. Faraday Soc. 63, 1699 (1967)]—the reaction being followed by measuring the decrease in light absorption of the ferricyanide complex at 4100 A. (see Table III). 

Mechanisms for both reactions are proposed, which are supported by the identification of several intermediate reactions. The role of various organic and inorganic reaction promoters is discussed. Amongst these, phosphine oxides are exceptionally efficient in that they induce high reaction rates combined with high selectivities. Reactions a) and b) potentially allow two-step, methanol/ /synthesis gas-based routes to ethyl acetate and proprio-nic acid, respectively. 

The oxidation of a series of alkyl and aryl thiols in aqueous alkaline solution has been studied in the presence of various metal ions. Quantitative amounts of disulfide were produced in all cases. The oxidation rate of thiols has been found to be affected by the geometric size and electron-directing properties of substituent groups in the organic chains of the thiols. The best three catalysts, when added as simple salts, have been found to be copper, cobalt, and nickel. The dependence of the rates of oxidation on the concentrations of reactants have been investigated in some detail. 

Fromment and Bishoff (1990) presented the possible expression of each of these terms in various cases, whereas Poulopoulos el al. (2001) have presented various rate laws for the catalytic oxidation of volatile organic compounds, as shown in Table 5.3. 

Recent emphasis has focused on the role of antioxidants in the general aging of humans. As pointed out by Stahelin (1999), key factors in the development of the aging processes are associated with a species capacity of repairing DNA and of the antioxidant defense of the body. Various organs of the body may respond to the oxidative stress at different rates and with different defense mechanisms. 

Significant enhancement effects of electron acceptors (additives) such as hydrogen peroxide, ammonium persulfate, potassium bromate, and potassium peroxymono-sulfate (oxone) on the Ti02 photocatalytic degradation of various organic pollutants were observed already in early investigations [376]. The results showed that these additives markedly improved the degradation rate of 2,4-dichlorophenol. The enhanced photocatalytic oxidation of sulfide ions on phthalocyanine modified titania was ascribed [377] to the additional formation of superoxide radicals. 

Intermediates in colloidal titania-catalysed photoreactions have been detected, and a study of the heterogeneous and homogeneous photooxidation of various organic compounds in both gas and liquid phases has associated the photocatalytic centre of the catalyst with the Ti-O bond. During light absorption the Ti ion changes its oxidation state and coordination number. The photocatalytic oxidation of ethane has been studied at room temperature, au d in particular the effect on the rate of ethame oxidation of the partial pressure of react ults, the UV light... 

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