Diffusion in Internal Oxidation Reactions

2012 ◽  
Vol 323-325 ◽  
pp. 283-288 ◽  
Author(s):  
David J. Young
Keyword(s):  
Metal Oxide ◽  
Gas Phase ◽  
Internal Oxidation ◽  
Metal Matrix ◽  
Oxidation Reactions ◽  
Alloy Component ◽  
Interfacial Diffusion ◽  
Penetration Kinetics ◽  
Oxidation Theory ◽  
Solvent Metal

When an alloy component is selectively oxidised but cannot reach the surface quickly enough to form a scale, then internal oxidation results. In this process, a gas phase oxidant dissolves in an alloy and diffuses inwards, reacting with a dilute solute metal to precipitate metal oxide or carbide, etc. Penetration kinetics are parabolic, the rate being controlled by oxidant diffusion and the concentration of reacting metal. Rates are predicted from classical oxidation theory on the basis that the reaction product is exceedingly stable, no solute metal remains in the reacted alloy, and oxidant diffusion is via a solvent metal matrix. This paper is concerned with situations where these approximations fail: the development of low stability precipitates and the growth of elongated precipitates which allow interfacial diffusion of the oxidant. Effects on the rates of internal oxidation are discussed.

Gas phase interaction with catalytic oxidation reactions

1972 ◽  
Vol 326 (1565) ◽  
pp. 215-227 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Maleic Anhydride ◽  
Catalytic Oxidation ◽  
Gas Phase ◽  
Major Part ◽  
Oxidation Reactions ◽  
Mixed Gas ◽  
Kinetics Of ◽  
Oxidation Of Benzene ◽  
Homogeneous Decomposition

Studies of the catalytic oxidation of benzene to maleic anhydride and carbon dioxide over vanadia/molybdena catalysts show that the major part of the reaction involves interacting gas and gas-solid processes. The results are consistent with a mechanism in which a benzeneoxygen adduct is formed catalytically, desorbs and then reacts to give maleic anhydride entirely in the gas phase. On the basis of this proposed mechanism, the kinetics of individual reactions have been investigated in some depth. The over-oxidation of maleic anhydride has been found to be not significant under the conditions of reaction. The kinetic relationships governing the homogeneous decomposition of the adduct and the oxidation of the adduct to maleic anhydride and to carbon dioxide have been established. The results show that essentially all of the anhydride originates from mixed gas-solid/gas reaction while substantial amounts of carbon dioxide are produced entirely catalytically.

Catalytic CO Oxidation by Gas-Phase Metal Oxide Clusters

2019 ◽  
Vol 123 (43) ◽  
pp. 9257-9267 ◽  
Author(s):  
Xiao-Na Li ◽  
Li-Na Wang ◽  
Li-Hui Mou ◽  
Sheng-Gui He
Keyword(s):  
Metal Oxide ◽  
Co Oxidation ◽  
Gas Phase ◽  
Catalytic Co Oxidation ◽  
Metal Oxide Clusters

scholarly journals Dioxygen dissociation over man-made system at room temperature to form the active α-oxygen for methane oxidation

2020 ◽  
Vol 6 (20) ◽  
pp. eaaz9776 ◽  
Author(s):  
Edyta Tabor ◽  
Jiri Dedecek ◽  
Kinga Mlekodaj ◽  
Zdenek Sobalik ◽  
Prokopis C. Andrikopoulos ◽  
...  
Keyword(s):  
Gas Phase ◽  
Room Temperature ◽  
Practical Importance ◽  
Oxidation Reactions ◽  
Reaction Conditions ◽  
Oxidation Of Methane ◽  
Oxidation Properties ◽  
Enzyme Functionality ◽  
Methane Utilization ◽  
Selective Oxidation Reactions

Activation of dioxygen attracts enormous attention due to its potential for utilization of methane and applications in other selective oxidation reactions. We report a cleavage of dioxygen at room temperature over distant binuclear Fe(II) species stabilized in an aluminosilicate matrix. A pair of formed distant α-oxygen species [i.e., (Fe(IV)═O)2+] exhibits unique oxidation properties reflected in an outstanding activity in the oxidation of methane to methanol at room temperature. Designing a man-made system that mimicks the enzyme functionality in the dioxygen activation using both a different mechanism and structure of the active site represents a breakthrough in catalysis. Our system has an enormous practical importance as a potential industrial catalyst for methane utilization because (i) the Fe(II)/Fe(IV) cycle is reversible, (ii) the active Fe centers are stable under the reaction conditions, and (iii) methanol can be released to gas phase without the necessity of water or water-organic medium extraction.

Catalytic fluorination of 2-chloropyridine over metal oxide catalysts in gas phase in the presence of HF

2012 ◽  
Vol 413-414 ◽  
pp. 149-156 ◽  
Author(s):  
Cindy Cochon ◽  
Thibaut Corre ◽  
Stéphane Celerier ◽  
Sylvette Brunet
Keyword(s):  
Metal Oxide ◽  
Gas Phase ◽  
Oxide Catalysts ◽  
Metal Oxide Catalysts
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