Oxidation Reactions in the Gas Phase

Oxidation Reactkns in the Gas Phase.— With a sound theoretical and experimental base established, the direct measurement of reaction temperatures has been applied in the study of oxidation reactions, and a hierarchy of complicity has been revved. Least complex among the systems studied appear to be the explosive oxidations of hydrazine and methylhydrazine. Both appear overwhelmingly thermal in origin  

Yet more complexity and variety of behaviour is found in the oxidation of hydrocarbons and related species. Such reactions again ndiibit multiplidty of ignition limits but in addition show oscillatory modes of reaction both in the slow reaction and in ignition phenomena. It is only within the past ten years that these systems have been successfully interpreted in the light of current theoretical ideas. These ideas we reserve until Section S. 

3 How may Stationary-state Conductive HieOTy be Extended to Complex Reactant Geometries  

In his first studies of the Fourier equation for temperature distribution in a reactive system, Frank-Kamenetskii restricted his attention to three shapes, the infinite slab, the infinite cylinder, and the sphere. For these three geometries (class A) the Laplacian operator can be expressed in terms of a single co-ordinate, and the steady-state problem is reduced to solving the ordinary differential equation 

Accurate general extensions of solutions to these problems are few. In 1960, Parks tackled the numerical solutions for the heat balance equation in the cube and the equicylinder in the Frank-Kamenetskii limit (e = 0) his work leads to dor = 2.52 and 2.78 respectively. More recently, Anderson and Zienkiewic have made numerical computations on both stationary and transient problems in various arbitrary geometries by means of finite-element methods. 

---

A simple model for the formation and growth of an aerosol at ambient conditions involves the formation of a gas product by the appropriate chemical oxidation reactions in the gas phase. This product must have a... 

With this in mind we found it worthwhile to investigate this oxidation reaction in the gas phase over a solid catalyst, thereby avoiding the formation of the by-products mentioned above. In this paper we describe some catalyst screening experiments and the development of a process using an heterogeneous catalyst. As will be shown, copper oxide based catalysts exhibit high... 

Thus, the experimentally determined ability of hydrogen peroxide to induce oxidation reactions in the gas phase is also observed for liquid-phase oxidation of substrates. 

The by-product, NO, then must be oxidized to NO2 for it to be reabsorbed. Because this oxidation reaction in the gas phase is time dependent, NO2 removal efficiency usually is limited to about 80% in a single fume scrubber when water is the scrubbing liquid. 

BrCl can be prepared by the reaction in the gas phase or in aqueous hydrochloric acid solution. In the laboratory, BrCl is prepared by oxidizing bromide salt in a solution containing hydrochloric acid. 

Some of the earliest experimental studies of neutral transition metal atom reactions in the gas phase focused on reactions with oxidants (OX = O2, NO, N2O, SO2, etc.), using beam-gas,52,53 crossed molecular beam,54,55 and flow-tube techniques.56 A few reactions with halides were also studied. Some of these studies were able to obtain product rovibrational state distributions that could be fairly well simulated using various statistical theories,52,54,55 while others focused on the spectroscopy of the MO products.53 Subsequently, rate constants and activation energies for reactions of nearly all the transition metals and all the lanthanides with various oxidant molecules... 

The model for phase transitions and chemical reactions takes into account thermal destruction of dust particles, vent of volatiles, chemical reactions in the gas phase, and heterogeneous oxidation of particles influenced by both diffusive and kinetic characteristics. 

Two chemical reactions in the gas phase were considered generalized volatiles component L oxidizing (unidirectional) and carbon monoxide CO oxidizing... 

Fig. 7.9 Heat flux and heat of reaction in the gas phase and in the condensed phase for an oxidizer-rich AP-HTPB propellant at low pressures below 0.1 M Pa.

Ethylene adds hypochlorous acid more readily than it adds either moist chlorine or hydrogen chloride. Bubbled into chlorine water, it is converted completely into ethylene chlorohydrin, and by the hydrolysis of this substance glycol is obtained. Ethylene chlorohydrin is important also because of its reaction with ammonia whereby mono-, di-, and triethanolamine are formed, substances which are used in the arts and are not without interest for the explosives chemist. Ethylene may be oxidized catalytically in the gas phase to ethylene oxide which reacts with water to form glycol and with glycol to form diglycol which also is of interest to the dynamite maker. 

For both the OVPO process and the MCVD process the correct temperature setting during the course of the respective process steps has an important bearing on the quality of the final preform. The reason is that both processes consist of a first step where reactions in the gas phase lead to soot particles which settle out afterwards, and of a second step where the soot is melted to a transparent glass. In the first step the efficiency for oxide formation critically depends on the temperature of the gas and differs from one oxide to another11. The second step is sensitive to temperature... 

A particular function of a catalyst can be initiation of radicals desorbing from the catalyst into the gas phase where they act as homogeneous catalysts in chain reactions. Such a mechanism is very likely to operate in methane coupling at high temperatures with basic oxide catalysts (No. 2) acting on methane molecules leading to methyl radicals that start chain reactions in the gas phase [11],... 

Fig. 7.21 Simplified scheme of interrelated photo-initiated oxidation and secondary radical reactions in the gas phase (atmospheric...

This book is about homogeneous reactions, that is, all kinds of reactions that occur within a single fluid phase. The term excludes reactions at interfaces, among them reactions of solids with fluids, heterogeneous catalysis, and phase-transfer catalysis. It does not exclude reactions in which a dissolved reactant is resupplied from another phase, as is the case, for example, in homogeneous hydrogenation or air oxidation reactions in the liquid phase in contact with a gas phase. 

---