Role of Lattice Oxygen

Unlike propene oxidation to acrolein or butene oxidation to maleic anhydride, oxygen is not incorporated into the selective oxidation product butadiene. However, water is formed together with butadiene, and it could conceivably be formed with lattice oxygen. There have been no isotopelabeling experiments to elucidate this. Similarly, it is not known whether the formation of any of the combustion products involves lattice oxygen. 

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In this study we examine the role of lattice oxygen from VPO catalysts in the oxidation of MEK. 

The use of isotopic techniques, especially 0/ 0 oxygen exchange, during mechanistic studies of the oxidative coupling of methane allows a great deal of information to be obtained concerning the role of lattice oxygen in the methane activation process. Ekstrom and Lapszewicz ... 

The role of lattice oxygen during the oxidative coupling reaction on many reducible metal oxides is interpreted in terms of a redox mechanism. 8ince a large number of diese catalysts can... 

Peil KP, Marcehn G, Goodwin JG, Jr, The role of lattice oxygen in the oxidative coupling of methane, in Wolf EE (ed.). Methane Conversion by Oxidative Processes-Fundamental and Engineering Aspects, Van Nostrand Reinhold, New York, pp. 139-145, 1992. 

The reason for the difference in the effectiveness between each of the crystal face to catalyze the ammoxidation of alkyl aromatics selectively is a result of the specific electronic character of the oxygen atoms associated with the vanadium atoms of the V2 O5 structure. As was learned about the role of lattice oxygen (0 ) in the selective ammoxidation of propylene to acrylonitrile (see above), hydrogen abstraction and oxygen insertion require oxygen atoms with nucleophilic character (79). On the other hand, nonselective oxidation is affected by electrophilic oxygen species, O2 and O . These are the intermediate species in the dissociative chemisorption and reduction of O2 to lattice (80). 

Dinse, A., Schomacker, R. and Bell, A. (2009). The Role of Lattice Oxygen in the Oxidative Dehydrogenation of Ethane on Alumina-Supported Vanadium Oxide, Phys. Chem. Chem. 

Saito K, Okuda K, Ikenaga N, Miyake T, Suzuki T (2010) Role of lattice oxygen of metal oxides in the dehydrogenation of ethylbenzene under a carbon dioxide atmosphere. J Phys Chem A 114 3845-3854... 

The 02 ion appears to play an important role in a number of photooxidation reactions (see Section VI,C) for example, the photo-oxidation of alkenes over TiOz. However, it seems likely that OJ is not, in many cases, active in the oxidation step but further conversion occurs to give a mononuclear species, not detected directly, which then oxidizes the adsorbed hydrocarbons. Photo-oxidation of lattice oxygen in the M=0 systems (e.g., V2Os supported on PVG) gives rise to an excited charge transfer state such as V4 + -0 . This excited state can react as O- either by addition to a reactant molecule or by an abstraction reaction (see Section V of Ref. /). In the presence of oxygen, 03 is formed which then reacts further with organic molecules. 

Sancier et al. (43) used oxygen-18 to examine the relative role of adsorbed versus lattice oxygen in propylene oxidation over a silica-supported bismuth molybdate catalyst as a function of temperature. At 400°C they observed the formation of predominantly acrolein[I60] rather than acrolein[I80], indicating significant participation of lattice oxygen. However, as the reaction temperature was decreased, the authors concluded that the role of adsorbed oxygen became more important. 

In other catalytic formulations, the role of Bi in the H-abstraction step may be played by Sb " and Te", while that of Mo in olefin chemisorption and NH insertion can be taken by Sb. The mobility of lattice oxygen, from... 

These results indicate that the isolated copper species on ZSM-5 have an activity for the decomposition reaction of NO different from that of the dimeric or polynuclear copper species, probably because there are different reaction mechanisms (237). The results obtained with the Cu(ll)ZSM-5 catalyst also suggest that Cu " ions promote the spontaneous low -tempera-ture dehydroxylation of nearby Brpnsted sites or the elimination of lattice oxygen anions which play a vital role in the decomposition of NO. When the dimeric or polynuclear species of Cu are present, the spontaneous elimination of the lattice oxygen bridging the two Cu"+ sites does not occur at low temperatures however, this reaction occurs at high temperatures. The activity for the decomposition of NO is nearly zero at about 573 K, but in the presence of O2 a different reaction mechanism is initiated and this results in the enhancement of NO conversion. Moreover, the presence of stronger Brpnsted sites in ZSM-5 can explain why only the CuZSM-5 catalyst exhibits much higher activity for the reduction of NO in NO-NH3-O2 reaction systems. 

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