Thermal non-catalytic

Hi-Chloroff A thermal (non-catalytic) process for removing chlorine from chlorinated hydrocarbon wastes containing either low or high concentrations of chlorine. Developed by Kinetics Technology International. See also Chloroff. 

Small reformers R D areas include compact and low cost reformers (1-5 kW) to convert fossil fuels (natural gas, gasoline) or biomass fuels (ethanol) to hydrogen via different processes (steam reforming, partial oxidation, auto-thermal, non catalytic hybrid steam reforming). Improvements in reformer efficiency, capacities and response times, and integration of purification unit are also being studied. Examples of projects include ... 

The four tautomeric monocyclic azepines are formally interchangeable by a series of 1,5-H shifts. Often, e.g. the parent 1//-azepine (80AG(E)1016), this isomerization is acid-and base-catalyzed. Many examples however, are known to occur under thermal non-catalytic conditions, and the accepted order of stability of azepines (i.e. 3H>4H >2H > 1H) is based on such observations. For example, the 4//-azepine (57) on heating for a few minutes at 190 °C undergoes consecutive 1,5-H shifts to give ultimately the 3H -azepine (58) (72CB982). The facile interconversion of 2H-azepines to 3H -azepines is similarly explained (76JOC543). 

Catalytic incineration (complete air oxidation) for the purification of gas streams is now quite commonly used in many applications (1-7), being preferred in these over thermal (non-catalytic) incineration and adsorption methods. It can offer advantages over thermal incineration in terms of costs, size, efficiency of destruction, and minimization of thermal NOx by-product formation. The catalytic incineration systems are now commonly employed in such applications as exhaust emission purification from a variety of industrial processes (including manufacture of organic chemicals and polymers) and air-stripping catalytic processes used to clean contaminated water or soil. 

These remarkable materials owe their efficacy to their ability to form appropriate unstable intermediates which then channel the course of a reaction in ways that are improbable in thermal non-catalytic reactions. The action of catalysts therefore depends on a reaction between the reactant and an active site on the catalyst surface. Since catalysts can be solids whose activity resides on the surface, or homogeneously dispersed fluids, it is best to think of the active site as a reactive center on the catalytic molecule, even if the molecule turns out to be a crystal of solid material. 

The thermal (non-catalytic) cracking of plastics occurs by a radical mechanism. The initiating radicals are formed by the effect of heat The instabUily of macromolecules under heat treatment is often due to the presence of anomalous weak links in the polymer. In these cases, low molecular weight models of the normal chain unit are much more stable than the polymer [47]. 

Kaloidas VE, Papayannakos NG (1989) Kinetics of thermal non-catalytic decomposition of hydrogen sulphide. Chem Eng Sci 44(11) 2493-2500... 

Thermal non-catalytic rearrangement of di(0-vinyl) dioxime in DMSO (120°C, 30 min) furnishes monopyrrole, which further is transformed into dipyrrole only at a higher temperature (140°C, 30 min). 

It has been proposed that protonation or complex formation at the 2-nitrogen atom of 14 would enhance the polarization of the r,6 -7i system and facilitate the rearrangement leading to new C-C bond formation. The equilibrium between the arylhydrazone and its ene-hydrazine tautomer is continuously promoted to the right by the irreversible rearomatization in stage II of the process. The indolization of arylhydrazones on heating in the presence of (or absence of) solvent under non-catalytic conditions can be rationalized by the formation of the transient intermediate 14 (R = H). Under these thermal conditions, the equilibrium is continuously pushed to the right in favor of indole formation. Some commonly used catalysts in this process are summarized in Table 3.4.1. 

This comprehensive article supplies details of a new catalytic process for the degradation of municipal waste plastics in a glass reactor. The degradation of plastics was carried out at atmospheric pressure and 410 degrees C in batch and continuous feed operation. The waste plastics and simulated mixed plastics are composed of polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile butadiene styrene, and polyethylene terephthalate. In the study, the degradation rate and yield of fuel oil recovery promoted by the use of silica alumina catalysts are compared with the non-catalytic thermal degradation. 9 refs. lAPAN... 

According to this scheme, the catalyst serves primarily to promote dehydrogenation. Cyclization of the hexatriene was shown years ago (JJ.) to occur thermally in the gas phase at temperatures well below these dehydrocyclization conditions. Thus, the overall reaction is projected to be the combination of several catalytic dehydrogenation steps and a non-catalytic cyclization step. This projection implies that the design of the catalytic reactor may be important in order to optimize the ratio of void space for cyclization and catalyst space for dehydrogenation. 

For PP degradation (Fig. 5), the non-acidic Ti-MCM41 and the Fe-ZSM-5 samples produced liquid hydrocarbons with yields about 90%, which is higher than that of non-catalytic thermal degradation. Similar results have been obtained for PS degradation, however, the activity of the catalyst with small pore sizes (ZSM-5) have had lower activity (no reaction observed below 350 °C). 

In actual in-situ coal gasification, numerous processes, i.e. oxidation, reduction, thermal cracking and a variety of catalytic as well as non-catalytic reactions, occur in overlapping zones, and to explore the chemistry of these reactions as single or consecutive unit processes is virtually impossible. It is, however, feasible to study the individual reactions under controlled conditions by simulating in-situ gasification in the laboratory. 

Plasmas can be classified as either thermal or non-thermal. " Thermal plasma is a highly energetic state of matter, characterized by thermal equilibrium between the three components of the plasma electrons, ions, and neutrals. However, it requires high-energy input to achieve high temperatures. Researchers at MIT used a non-catalytic thermal plasma technology to produce H2 from liquid hydrocarbons. Non-catalytic processes are beyond the scope of this work, and will not be discussed. 

The evolution of the dimensionless density profile across the soot layer is shown in Fig. 23. The initial gradual replenishment of the soot in the catalytic layer (at t = 140 s) is followed by sudden penetration events (t — 262 and 326 s) before the establishment of a steady state profile (at =531 and 778 s). Regarding the non-catalytic (thermal) layer only a gradual reduction of its thickness, accompanied by a very small reduction of its uniform density is observed. This simple microstructural model exhibits a rich dynamic behavior, however we have also established an experimental program to study the soot cake microstructure under reactive conditions. 

The catalysts which operate by means of an E2 mechanism give a high proportion of reaction products which are formed by the anti-elimination. This fact has been discussed in Sect. 2.1 and only few remarks need to be added here. Quantum chemical calculations [73] on the transition state of the dehydrochlorination of chloroethane, initiated by an attack of a basic species, confirmed the preference of the anti-elimination over the syn-mode. On the contrary, calculations on the transition state for non-catalytic (homogeneous) thermal elimination [201,202] confirmed the syn-elimination path. 

The future fortune of these radicals depends on the conditions of reaction proceeding for example, on the state of the reaction phase (liquid or gas), catalysts applied or thermal activation. The overall mechanism of non-catalytic H202 dissociation in a liquid is described by a selection of elementary reactions discussed in Chapter 6. 

In either case, in order to explain the molecular size shift and disappearance of the large molecules, we modified the model in two ways. First the molecular diameter of the asphaltene molecules are reduced by an amount directly proportional to their molecular volumes. Secondly, the disappearance of the large molecular-sized vanadium is treated as a non-catalytic first order reaction with a rate constant directly proportional to molecular volume. The vanadium which reacts thermally deposits... 

Vapor phase oxidation processes prevail over liquid phase processes, although the latter are sometimes used inlarge-scale chemical production when the products (i) can be easily recovered from the reaction medium, as interephthalic acid production, for example (ii) are thermally unstable (i.e., in the production of hydroperoxides and carboxylic acids, except for P-unsaturated compounds) and (iii) are very reactive at high temperature (i.e., epoxides, aldehydes and ketoses, with the exception of ethene oxide and formaldehyde). Liquid-phase oxidation is also preferred in fine chemicals production, although most processes are still non-catalytic. 

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