Effect of temperature on oxidation

Lowering the temperature of the reaction would certainly decrease the rate of acetal hydrolysis and thereby partially remove one of the causes of overoxidation. This would simultaneously decrease the rate of oxidation by periodate. Although no comprehensive study of the effect of temperature on oxidation rates has been made, the number of reactions successfully dealt with in the temperature range of 0 to 6°31 39 78 113 126 130 i33, i64, us, 203,210,266,267 indicates that lowered temperatures do not affect the rates unfavorably. In order to obtain the maximum of selective oxidation and the minimum of overoxidation, periodate oxidations should be performed at as low a temperature as is practicable in relation to the solvent system used and the solubility of the reactants therein. 

A second, highly reactive species of oxygen is ozone (O3). The effects of temperature on oxidation of carbons prepared from cherry stones as well as the kinetics of the reactions with ozone are reported by Gdmez-Serrano et al. (2002a, b). There is no doubt that if an... 

Surviliene, A. and Survila, A. (2002) Effect of temperature on oxide formation in ligand-deficient Cu Cu(II), ethylenedi-amine system. Russ. J. Electrochem., 38 (11), 1216-1219. 

Teraoka, R. Otsuka, M. Matsuda, Y. Chemical stability of ethyl icosapentate against autoxidation. I. Effect of temperature on oxidation kinetics, Pharm.Res., 1992, 9, 1673-1676. 

Fig. 13. Effect of temperature on discharge efficiency (a) at 270 mA-h of miniature 2inc—mercuric oxide batteries type EP675E, and (b) at 175 mA-h of...

Bianchi, G., Corguetti, A., Mazza, F. and Torchio, S., Electronic Properties of Oxide Films and Pitting Susceptibility of Type 304 Stainless Steel , Corros. Sci., 12, 495 (1972) Szkiarska-Smialowska, Z. and Mankowski, J., Effect of Temperature on the Kinetics of... 

Figure 4.12. Effect of temperature on the Tafel plots and corresponding I0 values of a Ag catalyst-YSZ interface during C2H4 oxidation on Ag.12 Reprinted with permission from Academic Press.

Fig. 1 Effect of temperature on NH3 oxidation. Closed symbols electric finnace, open symbols microwave heating,, O NH3 conversion, A, A N2 selectivity,, NO selectivity, BO N2O selectivity.

The effects of temperature on carotenoid content can be considered from three perspectives (1) evaluation of stability or retention of carotenoids, (2) study of the chemical changes (isomerization, oxidation, epoxy-furanoid rearrangement), and (3) their effects on the nutritional value and other carotenoid actions in humans. The first two topics are discussed in the following sections. The third is presented in Section 3.2.4.1 of Section 3.2. 

Markovic NM, Schmidt TJ, Grgur BN, Gasteiger HA, Behm RJ, Ross PN. 1999. The effect of temperature on the surface process at the Pt(lll)-liquid interface Hydrogen adsorption, oxide formation and CO oxidation. J Phys Chem B 103 8568. 

In order to illustrate this principle, let the effect of temperature on the equilibrium constant of an exothermic reaction, involving the oxidation of a metal to its oxides, be considered. Upon increasing the temperature of this reaction some of the metal oxides will dissociate into the metal and oxygen and thereby reduce the amount of heat released. This qualitative conclusion based on Le Chatelier s principle can be substantiated quantitatively from the Varft Hoff isochore. 

In addition to the dependence of sorption on the organic fraction of the sorbent, and the KQw of the sorbate, Chiou et al. (13) cite the following observations as support for the hypothesis that the sorptive mechanism is hydrophobic partitioning into the organic (humic) fraction of the sediments (1) the linearity of the isotherms as the concentration approaches solubility, (2) the small effect of temperature on sorption, and (3) the lack of competition between sorbates for the sorbent. These arguments also illustrate the applicability of the approach for modeling sorption on hydro-phobic compounds an approach which has been criticized when used in the context of adsorption of trace metals onto oxides (17). 

The Mallard-Le Chatelier development for the laminar flame speed permits one to determine the general trends with pressure and temperature. When an overall rate expression is used to approximate real hydrocarbon oxidation kinetics experimental results, the activation energy of the overall process is found to be quite high—of the order of 160kJ/mol. Thus, the exponential in the flame speed equation is quite sensitive to variations in the flame temperature. This sensitivity is the dominant temperature effect on flame speed. There is also, of course, an effect of temperature on the diffusivity generally, the dif-fusivity is considered to vary with the temperature to the 1.75 power. 

Silica from zeolite migrates less readily. In the magnesia-alumina system, spinel, as identified by X-ray diffraction, is inactive for SO2 removal. The effect of temperature on steam stability, oxidative adsorption and reductive desorption of SO2 are described. Five commercial catalyst types are ranked for SOx removal. 

The low-temperature electrochemistry technique is useful in the study of electrode reactions involving unstable products or intermediates. Lowering the temperature by 30-40 °C decreases the reaction rate of the unstable species to one-tenth of the original value. It is equivalent to a ten-fold increase in the voltage scan rate. Figure 8.22 shows the effect of temperature on the cyclic voltammo-gram for the oxidation of 1,2,3,6,7,8-hexahydropyrene. At ambient temperatures, it does not give a re-reduction peak Fiowever, at -60 °C, reversible oxidation and rereduction waves are observed. The techniques of low-temperature electrochemistry... 

Fig. 8.22 Effect of temperature on the cyclic voltammogram for the oxidation of 1,2,3,6,7,8-hexahydropyrene (2.5 mM) at a platinum electrode in 0.1 M BU4NCIO4-butyronitrile. Scan rate 50 mV s-1 [76a]...

Since product distributions depend on the relative rates of competing reactions, effects of temperature on products depend on differences in activation energies, AE. For each pair of competing reactions of the tert-Bu02 radicals, the following AE values (in kilocalories per mole) and qualitative effects of increasing temperature are estimated. Some of these values were considered under Liquid-Phase Oxidations. ... 

The effect of temperature on the yields of the three addition products, a-butene oxide, n-butyraldehyde, and methyl ethyl ketone, and of a fragmentation product, carbon monoxide, is shown in Figure 3. It is seen that as temperature is increased from 25-200°C. the yields of the... 

Fig. 39.—The Effect of Temperature on the Oxidation of Ammonia with Platinum as Catalytic Agent.

Studiengesselschaft Kohle m.b.H. (2) reported the effect of temperature on solubility level in supercritical gas. The solubility is highest within 20 K of the critical temperature and decreases as temperature is raised to 100 K above the critical temperature. At temperatures near the critical temperature, a sharp rise in solubility occurs as the pressure is increased to the vicinity of the critical pressure and increases further as the pressure is further increased. Less volatile materials are taken up to a lesser extent than more volatile materials, so the vapor phase has a different solute composition than the residual material. There does not seem to be substantial heating or cooling effects upon loading of the supercritical gas. It is claimed that the chemical nature of the supercritical gas is of minor importance to the phenomenon of volatility amplification. Ethylene, ethane, carbon dioxide, nitrous oxide, propylene, propane, and ammonia were used to volatilize hydrocarbons found in heavy petroleum fractions. 

Figure 6. Effect of temperature on the weight loss of sulfided iron oxide sorbents in sulfur dioxide atmosphere.

Figure 2.23. Effect of temperature on the activity of tyrosinase (0.148 mg) and 8-Mn02 (2.0mg) at an initial pH of 6.0. Reprinted with permission from Naidja, A., Huang, R M.,Dec, I, and Bollag, J.-M. (1999). Kinetics of catechol oxidation catalyzed by tyrosinase or 8-Mn02. In Effect of Mineral-Organic-Microorganism Interactions on Soil and Freshwater Environments, Berthelin, I, Huang, R M., Bollag, J.-M., and Andreux, F., eds., Kluwer Academic/ Plenum Publishers, New York, 181-188.

Figure 8.3. Effect of temperature on the kinetics of Cr(III) oxidation in moist Hagerstown silt loam soil. [From Amacher and Baker (1982), with permission.]...

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