High oxidation rate

Molybdenum High melting point less dense than tungsten or tantalum moderately ductile at room temperature Extremely high oxidation rate (volatile oxide)... 

When variable-valence metals are used as catalysts in the oxidation of hydrocarbons, the chain termination via such reactions manifests itself later in the process. This case has specially been studied in relation to the oxidation of paraffins to fatty acids in the presence of the K Mn catalyst [57], which ensures a high oxidation rate and a high selectivity of formation of the target product (carboxylic acids). As the reaction occurs, alcohols are accumulated in the reaction mixture, and their oxidation is accompanied by the formation of hydroxyperoxyl radicals. The more extensively the oxidation occurs, the higher the concentration of alcohols in the oxidized paraffin, and, hence, the higher is the kinetic... 

In the field of wastewater treatments, thermally activated persulfate has also been proposed and tested in a process called direct chemical oxidation (DCO) (Anipsitakis and Dionisiou 2002). In addition, the available literature contains promising experimental results at high-temperature range (110-390°C). These results demonstrate that use of this oxidant permits high oxidation rates to be achieved, i.e., the elimination of 4-chloro-3-methylphenol is completed with a very short reaction time (3 < i/2 < 59 s) (Kronholm et al. 2001). 

Figure 3 shows the decay in the concentration of S(IV) for rain water collected at Hiyoshi, Yokohama. Five mL of 2.5 mM (S(IV) solution was added to 195 mL of rain water, and the initial concentration of S(IV) was adjusted to 62.5 pM. The decay of S(IV) concentration was linear as seen in Figure 3. This is consistent with a first order reaction with respect to S(IV). A difference of oxidation rate between filtrated and non-filtrated samples was observed. The high oxidation rates in the non-filtrated rain water is assumed to be due to the presence of suspended particulate matter.

The high oxidation rates of EPA and DHA and the instability of their hydroperoxides caused the rapid formation of secondary products such as volatile aldehydes and other compounds, which, in turn, impart flavor reversion in fish oils (56). The hydroperoxides produced from autoxidation of EPA (73) and DHA (74) have been identified but not quantified. They form eight and ten isomers, respectively. Noble and Nawar (75) analyzed the volatile compounds in autoxidized DHA and identified a number of aldehydes. Most of the aldehydes identified could be explained by the p-scission of alkoxy radicals generated by the homolytic cleavage of each isomer of the hydroperoxides as shown in Figure 9. 

A small correction of a few percent must be applied to fluxes calculated from equation 7, because every 60- mL sample is replaced with lake water from outside the chamber. The Mn concentration of this lake water has also been analyzed. The measured fluxes vary between 5.5 mmol/m2 per day in July and a minimum of 0.5 mmol/m2 per day in April. We therefore conclude that the high oxidation rates in summer are balanced by similar Mn reduction rates at the sediment-water interface and that pore water analyses on the millimeter scale would be required to quantify the steep Mn(II) gradients during summer. 

Straightforward application of an oxidation catalyst to a flow through monolith will result in the oxidation of adsorbed hydrocarbons and partly the graphitic nuclei of the soot. This system is able to reduce particulate emissions up to 50 % and is considered to be an intermediate solution [1]. The ultimate goal will be the complete removal of the soot. In general, in soot oxidation two sohds, namely catalyst and soot, and a gas phase are involved. The interaction between the catalyst and the soot under practical conditions is poor. To achieve sufficiently high oxidation rates, this contact between catalyst and soot has to be improved [2]. 

In air, carburising atmospheres and sulphidising/oxidising atmospheres all alloys showed excellent corrosion resistance due to the formation of protective oxide scales. It was found that the concentration of aluminium or chromium does not significantly effect the corrosion behaviour in any of these environments. 10 wt% aluminium, probably even less, are sufficient to enable the formation of protective Al203-scales even at temperatures as low as 650°C. Overdoping with reactive elements (mischmetal), however, causes high oxidation rates in air and should be avoided. 

Thus a connection to regions of higher oxygen partial pressure is obtained and instead of nitrides titanium oxide is formed at the metal/oxide interface. As a consequence local temporary regions of high oxidation rate are formed within the scale which may lead to nodules observed on the surface of the oxide scale. At higher temperatures such cracks arc not found possibly because of an increased plasticity of the aluminium depleted subsurface zone or because of a rapid healing rate due to enhanced diffusion... 

Given the high oxidation rates of silicon-terminated multilayer films, other capping layer materials have been studied extensively. Oxidation can be appreciably reduced with protective capping layers. Extended lifetimes have been reported for ruthenium (Ru)-capped and carbon-capped ML mirrors. Ruthenium... 

Very high oxidation rates can be expected when an alloy yields a scale consisting of a melt providing fast flow of ions and a sohd phase providing easy flow of electrons. A model experiment for such a case was also proposed by Wagner [122]. When Ni is covered by a borate melt, oxidation can take place only by dissolution and diffusion of oxygen in the melt to the metal surface. 

Local cell action can lead to high oxidation rates, when by close contact of oxides and melt a large area is presented for the cathodic reaction. The oxides provide the fast transport of electrons and the melt the fast transport of ions. Transport of electrons is possible also by cations that are oxidized at the surface of a melt and reduced at the interface melt/alloy, for example, Fe +-Fe ", and so... 

Catalytic NH3 oxidiser with platinum-based catalyst This is necessary to achieve high oxidation rate Escape of unreacted ammonia if catalyst malfunctioning occurs Catalyst arrester is necessary to minimise the loss of catalyst... 

Lucarini and co-workers have determined the distribution of the nitroxide radicals in UV-irradiated PP containing a hindered amine stabilizer by one-dimensional (ID) ESRI. The spatial variation of nitroxide intensity in the thicker samples irradiated for longer times was explained by the diflnsion-limited oxidation (DLO) concept. The DLO regime and high oxidation rates lead to narrow penetration depth of oxygen. Recently, Marek et al. ° reported ID ESRI experiments on polystyrene and polypropylene plaques exposed to thermal aging and UV irradiation. 

---