Thermal/oxidation processes

Vanoppen et al. [88] have reported the gas-phase oxidation of zeolite-ad-sorbed cyclohexane to form cyclohexanone. The reaction rate was observed to increase in the order NaY < BaY < SrY < CaY. This was attributed to a Frei-type thermal oxidation process. The possibility that a free-radical chain process initiated by the intrazeolite formation of a peroxy radical, however, could not be completely excluded. On the other hand, liquid-phase auto-oxidation of cyclohexane, although still exhibiting the same rate effect (i.e., NaY < BaY < SrY < CaY), has been attributed to a homolytic peroxide decomposition mechanism [89]. Evidence for the homolytic peroxide decomposition mechanism was provided in part by the observation that the addition of cyclohexyl hydroperoxide dramatically enhanced the intrazeolite oxidation. In addition, decomposition of cyclohexyl hydroperoxide followed the same reactivity pattern (i.e., NaY < BaY... 

The zero-emission energy recycling system (ZEROS) is a closed-loop thermal oxidation process that incinerates waste and recycles flue gas emissions for electrical co-generation. The technology uses a two-stage plasma torch combustion system, energy recovery system, and combustion gas cleanup systems. 

The thermal oxidation process is an essential feature of planar-device fabrication and plays an important role in the diffusion of dopants in Si. In the thermal oxidation process, Si reacts with either oxygen or water vapor at temperatures between 600 and 1250 °C to form Si02. The oxidation reaction may be represented by the following two reactions ... 

Process Variables. The thermal oxidation process is a direct function of process variables, including the condition of the silicon surface. The following are important factors that affect thermal oxidation ... 

The second step (eq. 4.5) is a thermal oxidative process. This initiates the reaction of ZDDP with oxygen, and enhances the decomposition. Since oxygen and/or hydroperoxide is present in the oil, decomposition is not a pure thermal degradation. The main products on the surface are zinc polyphosphates with minor amounts of zinc sulfides. As the rubbing continues, the polyphosphate layer comes into closer contact with water in oil and is hydrolyzed to give short-chain polyphosphates (eq. 4.6). 

Further investigation of the nature of these films4 has shown that there is about 2.7% Cl remaining in the completed film. Upon exposing them to a thermal oxidation environment, it was discovered that the interface between the oxide and silicon was etched and film adhesion was lost—the films flaked off. Apparently, the thermal oxidation process released bound chlorine in the oxide which then diffused to the interface where it attacked the silicon. 

The mechanism of action of an effective fire retardant acting in the vapor phase should inhibit one or both reactions (Equation 4.2 and Equation 4.3) because they have a paramount effect on the increase of the overall rate of thermal oxidation process occurring in the flame. Indeed, the reaction represented by Equation 4.2 increases radical concentration while reaction represented by Equation 4.3 increases the temperature. From a mass spectrometry study of species sampled in low-pressure flame,4 it is evident that the introduction of halogen species into a premixed CH4/02 flame leads to the production of the hydrogen halide, HX, early in the flame. It was also observed that the production of H2 is enhanced. This provides evidence for removal of H atoms from the flame and the predominant reaction is considered to be... 

Furthermore, the chemical structure of networks are changed by thermal oxidation reactions 17,23,24F These are rather important for epoxy networks with aliphatic amines since they usually take place in the presence of air at T 130 °C. In aromatic amine-based polymers this kind of reaction becomes important at T > 220° 240 °C 17-23>. The only exception are polymers with a large excess of epoxy groups in the initial mixture. For example, the polymer with P = 0.4 23) starts loosing its weight at 160 °C17 23,24). All polymers considered in this paper are prepared from mixtures with 0.6 P 1.6. Cure and post-cure treatment temperatures are below 190 °C. This means we may not consider thermal oxidation processes in our structural analysis of the networks. 

One could also include the thermal black method in the group of thermal-oxidative processes, with the distinction that energy generation and decomposition reaction are not simultaneous. However, the fact that the actual carbon black formation takes place in the absence of oxygen and at decreasing temperatures results in carbon black properties that are markedly different from those achieved with thermal-oxidative processes. 

The increasing amounts of chlorinated volatile organic compounds (VOC), such as 1,2-dichloroethane (DCE) and trichloroethylene (TCE), released in the environment, together with their suspected toxicity and carcinogenic properties, have prompted researchers world-wide to find clean effective methods of destruction [1]. The abatement of chlorinated volatile organic compounds by catalytic combustion has been widely utilised in several technical processes. The lower temperatures required for catalytic combustion result in a lower fuel demand and can therefore be more cost effective than a thermal oxidation process [2]. In addition, the catalytic process also exerts more control over the reaction products and is less likely to produce toxic by-products, like dioxins, which may be generated by thermal combustion [3]. 

Table 5.2 Mechanical and thermal-oxidative processes of VI improvers...

Commercial polymers are believed to contain reactive groups such as hydroperoxide, carbonyl, and unsaturated groups. These groups often play important roles for the thermal oxidation processes of the polymers (1,2,9,10,43,44). Therefore, one may consider also the effects of the oxidation products originating from these reactive groups at the very beginning of the oxidation, when the mechanism of the copper-catalyzed oxidation of the polymer was discussed. Further experiments on the effects of various oxidation products on the thermal oxidation of the polymer will be published. 

The purpose of the injection subassembly is to inject the sample at an average rate of about IpL/s and an instantaneous rate that never exceeds that which would starve the thermal oxidation process of oxygen and so cause incomplete combustion. Also, any carbonization of the sample within the injector must be avoided. The sample is driven by a flow of inert carrier gas (argon) that is controlled by a combination of a flow restricter (MMVl) and a pressure regulator (LPRl). The injector, which is a stainless steel tube, penetrates the pyrolysis tube to a depth where the temperature is high enough to ensure sample volatilization within the injector while avoiding... 

In practice, the choice of WI is based on the analysis of service, design, economic and other factors. An efficient means of improving wear resistance of the polyamide-steel 45 friction pair turns out to be inhibition of the thermally oxidative and destructive processes in the polymer surface layers to avoid the formation of corrosion-active oxide compounds. It is possible to break this unfavorable cycle by the introduction of antioxidants into the polymer composition, thus disabling macroradicals through the reactions of mechanochemical synthesis, polyamide alloying by functional additives forming separating layers or more thermally stable products, and so on [108]. Application of WI with this aim abates undesirable thermally oxidative processes in polyamide... 

The Tt, Td and of the materials based on CFD increase with the introduction of Cl except for VNHL-20, which shows a reduced CFD Tt, and Td, evidently due to its own low thermal resistance. The inhibitors are likely to assist in binding of formaldehyde formed during CFD destruction and lead to decomposition of the copolymer macromolecular chain. In compositions on a polyamide base. Cl inhibit thermally oxidative processes that accelerate thermal decomposition of the polymer, elevating Tt and Td by 5-10°C. 

In order to provide a more suitable model research is underway at several laboratories as well as the exploration of several novel film growth techniques. Integrated circuit manufacturing demands will continue to drive research at improving the thermal oxidation process step. 

Concerning the thermal oxidation process (Fig. 2b), the formation of metal oxide nanowires is achieved with the oxidation of a metal film in controlled environment. Pressure, temperature and atmosphere composition are crucial for the unidirectional... 

The diverse behavior of PP and PP/MWCNT nanocomposites with 1 wt%, 3 wt%, and 5 wt% of MWCNT(3). Figure 3 shows that the influence of MWCNTs on the thermal oxidation process resulted in higher thermal-oxidative stabihty of PP/MWCNT nanocomposites. It is possible to see a regular increase in the temperature values of the maximum mass loss rates (up to 60°C) for the PP/MWCNT as compared to pristine PP (Figure 3). 

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