Intrinsic Mechanisms of Oxidation Reactions as Revealed by Gas-Phase Experiments

Author(s):  
Detlef Schröder ◽  
Helmut Schwarz

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.


2020 ◽  
Vol 6 (20) ◽  
pp. eaaz9776 ◽  
Author(s):  
Edyta Tabor ◽  
Jiri Dedecek ◽  
Kinga Mlekodaj ◽  
Zdenek Sobalik ◽  
Prokopis C. Andrikopoulos ◽  
...  

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.


2017 ◽  
Vol 41 (15) ◽  
pp. 7491-7505 ◽  
Author(s):  
S. Vijayakumar ◽  
C. B. Ramya ◽  
Avinash Kumar ◽  
B. Rajakumar

Cl atom initiated photo oxidation kinetics of cyclohexene and cycloheptene.


1997 ◽  
Vol 178 ◽  
pp. 45-60 ◽  
Author(s):  
A.G.G.M. Tielens ◽  
D.C.B. Whittet

IR spectra of sources associated with molecular cloud material show a variety of absorption features attributed to simple molecules, such as H2O, CO, CH3OH, CO2, CH4, and OCS in icy grain mantles. These identifications are reviewed. These molecules are formed through accretion and reaction of gas phase species on grain surfaces. The high abundance of CH3OH and CO2 point towards the importance of hydrogenation and oxidation reactions in this process. Observations also show that thermal outgassing is of great importance for the composition of interstellar ice mantles. Both these processes are discussed in some detail.


1994 ◽  
Vol 13 (10) ◽  
pp. 4072-4081 ◽  
Author(s):  
Matthew F. Ryan ◽  
Andreas Fiedler ◽  
Detlef Schroeder ◽  
Helmut Schwarz

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