Hydrocarbons oxidation reactions

Reaction 21 is the decarbonylation of the intermediate acyl radical and is especially important at higher temperatures it is the source of much of the carbon monoxide produced in hydrocarbon oxidations. Reaction 22 is a bimolecular radical reaction analogous to reaction 13. In this case, acyloxy radicals are generated they are unstable and decarboxylate readily, providing much of the carbon dioxide produced in hydrocarbon oxidations. An in-depth article on aldehyde oxidation has been pubHshed (43). 

Hydrocarbon Oxidation. The oxidation of hydrocarbons (qv) and hydrocarbon derivatives can be significantly altered by boron compounds. Several large-scale commercial processes, such as the oxidation of cyclohexane to a cyclohexanol—cyclohexanone mixture in nylon manufacture, are based on boron compounds (see Cylcohexanoland cyclohexanone Eibers, polyamide). A number of patents have been issued on the use of borate esters and boroxines in hydrocarbon oxidation reactions, but commercial processes apparently use boric acid as the preferred boron source. The Hterature in this field has been covered through 1967 (47). Since that time the Hterature consists of foreign patents, but no significant appHcations have been reported for borate esters. 

Since the overall order of most hydrocarbon oxidation reactions can be considered to be approximately 2, Eq. (7.23) takes the form of the so-called Semenov expression... 

The lower catalytic activity shown by the Pt/Al203 catalyst is probably due to the greater tendency of this catalyst to promote the hydrocarbon oxidation reaction [59, 95]. 

Ionic liquids are characterized by low vapor pressure, permitting operation in a wide temperature range without causing detrimental effect to the catalyst or the ionic liquid. All of Co(II)-IL/Support catalysts were characterized by TGA. Figure 2 illustrates that the novel catalyst system was stable up to almost 360°C. This has allowed us to utilize this catalyst system for applications other than Just hydrocarbon oxidation reactions. 

Extending the definition of n-type and p-type reactions, as defined by Vol kenshtein (21) to the electron transfer step, it would seem that the only reaction given by Equation 1 is a p-type reaction. This reaction would be accelerated by the increase in the value of free hole concentration. On the other hand, all other reactions besides the one given by Equation 1 are n-type and would be accelerated by the increase in free electron concentration. Hydrocarbon oxidation reactions catalyzed by solid oxides are accompanied by oxidation and reduction of the catalyst and the degree of the stoichiometric disturbance in the semiconductor changes. The catalytic process in the oxidation of 2-methylpropene over copper oxide catalyst in the presence of Se02 can be visualized as ... 

Selective hydrocarbon oxidation reactions are characterised by both high activation energies and heats of reaction. If the desired partial oxidation products are to be safeguarded and the catalyst integrity ensured it is essential that close temperature control be maintained. In spite of the obvious attractions of the fluid bed for this purpose, mechanical considerations normally dictate that a multi-tubular fixed-bed reactor, comprising small diameter tubes between 2-4 cms. diameter, be used. 

The ranges of experimental variables covered (Table 1) span those of several hydrocarbon oxidation reactions, among which are o-xylene, benzene and n-butane. Only minor extrapolations are required in ethylene oxidation, and these are safely realised by the model developed in the second part of this paper. 

M0O3 phase in various environments. Hydrocarbon oxidation reaction conditions led to extensive disintegration of the bulk structure of the heteropoly acid. 

A photochemically driven reaction that mimics biological photosynthesis, electron-transfer, and hydrocarbon-oxidation reactions is described. The reaction occurs at room temperature and uses 2 as the ultimate oxidant. Most importantly, the reaction can be run for hours without significant degradation. This means that the oxidation of low molecular weight alkanes by O2, which proceeds at a lower rate than for hexane, can be investigated. Further studies are underway to determine the detailed reaction mechanisms involved in the photochemical reaction and the relative contributions of various oxidative pathways. Transient absorption and Raman spectrocopic techniques will also be applied to determine reaction rates. 

In its literal form, this reaction is only of academic interest because a molecule is unlikely to break up or isomerize irreversibly in two or more different ways. However, situations frequently encountered in practice are those of multistep parallel first-order decomposition reactions and of parallel reactions that involve coreactants but are pseudo-first order in the reactant A. An example of the first kind is dehydrogenation of paraffins, examples of the second kind include hydration, hydrochlorination, hydroformylation, and hydrocyanation of olefins and some hydrocarbon oxidation reactions. All these reactions are multistep, but the great majority are first order in the respective hydrocarbon, and pseudo-first order if any co-reactant concentration is kept constant. 

Cool-flames arise for some ranges of experimental conditions for many other hydrocarbon oxidation reactions. Chapter 6 presents many p-T ignition diagrams for different hydrocarbon fuels, all of which have a... 

Until recently it was further assumed that the hydrocarbon oxidation reactions have equilibrated prior to the onset of NO formation because the NO reactions are relatively much slower (5) at temperatures of stoichiometric hydrocarbon-air combustion and because they take place over an extensive portion of the mixing region. Fenimore (6) and Harris et al. (7) have conducted recent experimental studies of NO formation in atmospheric flat flames their data support this simplified picture for posf-combustion-zone formation. However, Fenimore (6) noted a substantial amount of NO was formed very rapidly in the flame front of methane-air and ethylene-air flames but not in CO-air or H2-air flames. Figure 1 shows Fenimores data on NO formation in four ethylene-air flames as a function of reaction time from the burner surface to the probe tip. The positive intercepts are indicative of flame zone or prompt NO. Fenimore subsequently postulated that reactions such as... 

Table 1 Fixed-bed. vs. fluidized-bed reactors for selective hydrocarbon oxidation reactions...

It is very difficult to establish kinetic laws for hydrocarbon oxidation first of all due to the high endothermicity of this reaction resulting in sintering of the catalyst, in surface changes, and in the intensification of side processes. This is probably the reason why the kinetics of a number of hydrocarbon oxidation reactions is insufficiently known, and the data reported in literature are scarce. 

To find out the nature of the effect of impurities on the selectivity of hydrocarbon oxidation reactions, Enikeev, Isaev and Margolis (102) attempted to find out the relationship between the electron work function of a modified catalyst and the reaction rates and activation... 

Moreover, the close parallelism between the reaction rate for C3 and C4 oxidation at 570 K and total oxygen adsorption in this series of LaBC>3 oxides obtained by Kremenic et al. (1985) indicates that these hydrocarbon oxidation reactions occur through a mechanism in which adsorbed oxygen is the dominant O species participating in the process. 

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