Heterogeneous reactions, oxides

Exothermic oxidation—reduction reactions provide the energy released in both propellant burning and explosive detonation. The reactions are either internal oxidation—reductions, as in the decomposition of nitroglycerin and pentaerythritol tetranitrate, or reactions between discrete oxidizers and fuels in heterogeneous mixtures. 

Butane-Based Fixed-Bed Process Technology. Maleic anhydride is produced by reaction of butane with oxygen using the vanadium phosphoms oxide heterogeneous catalyst discussed earlier. The butane oxidation reaction to produce maleic anhydride is very exothermic. The main reaction by-products are carbon monoxide and carbon dioxide. Stoichiometries and heats of reaction for the three principal reactions are as follows ... 

Similar heterogeneous reactions also can occur, but somewhat less efticientiy, in the lower stratosphere on global sulfate clouds (ie, aerosols of sulfuric acid), which are formed by oxidation of SO2 and COS from volcanic and biological activity, respectively (80). The effect is most pronounced in the colder regions of the stratosphere at high latitudes. Indeed, the sulfate aerosols resulting from emptions of El Chicon in 1982 and Mt. Pinatubo in 1991 have been impHcated in subsequent reduced ozone concentrations (85). 

The cathode reaction involves reduction of silver oxide to metallic silver [7440-22-4J. The reaction is a two-phase, heterogeneous reaction producing a substantially constant voltage during discharge. Some manganese dioxide may be added to the cathode, as in the case of mercury oxide cells. 

Heterogeneous reactions these various processes are cyclic and continuous, taking place in all sections of the boiler from the economizer to the condensate lines and including suspended ferric oxide and cupric oxide particles. Unless the hydrazine overfeed is extremely substantial (say, six to seven times theoretical), these latter reactions tend to predominate ... 

To describe hypergolic heating, Anderson and Brown (A10) proposed a theoretical model based upon spontaneous exothermic heterogeneous reactions between the reactive oxidizer and a condensed phase at the gas-solid interface. In these studies, the least complex case was considered, i.e., the one in which the solid phase is instantaneously exposed to a stagnant (nonflowing) gaseous oxidizer environment. This situation can be achieved experimentally provided the sample to be tested is suddenly injected into the desired environment in a manner designed to minimize gas flow. 

Fig. 20. Heterogeneous reactions occurring at oxidizer-particle-polymeric-binder interface (A6).

The chemical properties of oxide surfaces have been studied by several methods, including oxygen exchange. This method has been used to investigate the mechanisms of heterogeneous reactions for which oxides are active catalysts [36]. The dimerization step does not necessarily precede desorption and Malinin and Tolmachev [634], in one of the few reviews of decomposition kinetics of solid metal oxides, use this criterion to distinguish two alternative reaction mechanisms, examples being... 

Many important industrial reactions rely on heterogeneous catalysts, yet there are inherent drawbacks to heterogeneous reactions. Such reactions occur only when the reactants contact the solid surface of the catalyst. Catalysis can be much more efficient when the catalyst is dissolved in the solvent where the reaction occurs. Unfortunately, the main catalysts used by industry, metals and metal oxides, are not soluble in traditional solvents. 

In conclusion, we note that the appearance of hydrogen atoms in the gas volume in catalytic reaction of dehydration of alcohol at low pressures observed in [25] by the sensor technique confirms that dehydration of alcohol on the surface of the zinc oxide catalyzer yields hydrogen atoms. In other words, this heterogeneous reaction does not result in production of hydrogen molecules through the process... 

Temperature according to thermodynamics prediction, nickel oxide is reducible by hydrogen at all practical temperatures. However, this heterogeneous reaction,... 

Heterogeneous reactions facilitated by supported reagents on inorganic oxide surfaces have received attention in recent years, both in the laboratory as well as in industry. Although the first description of the surface-mediated chemical transformation dates back to 1924 [13], it was not until almost half a century later that the technique received extensive attention with the appearance of several reviews, books and account articles [14—22],... 

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