Chemisorption homolytic

It is proposed that hydrated or dehydrated titaniumperoxo compounds are formed in TS-1 by H2O2 chemisorption on the titanyl (Ti 0) group, and that these complexes constitute the actual oxidants [96]. In the particular case of alkane oxidation, a homolytic reaction mechanism is proposed, as is tentatively represented in scheme 6 [114]. 

A.B. Anderson, Z.Y. Al-Saigh W.K. Hall (1988). J. Phys. Chem, 92, 803-809. Hydrogen on M0S2. Theory of its heterolytic and homolytic chemisorption. 

If the experimental conditions prior to recording the UV diffuse reflectance spectra are such that exclusively the saturation limited irreversible heterolytic H2 chemisorption (I) may occur, the intensity loss of the absorption band at 270 nm is small (Fig.6d) as compared to the pretreatment in terms of UV induced homolytic H2 splitting (Figs. 6b and c). This shows that the majority of the 3-coordinated O anions which exhibit a uniform UV excitation at 270 nm, are not able to split H2 heterolytically in the dark. For this purpose the specific site must — as discussed above — fulfill an additional requirement, namely, of being constituent of a low coordinated anion vacancy. 

Adsorption of reactants on the surface of a catalyst represents the first elementary step in a catalytic reaction cycle. Chemisorption and physisorption are two kinds of adsorption, and differ according to the type and strength of bond. In physisorption, the adsorption bond is due to the rather weak van der Waals interactions between permanent or induced dipoles. Chemisorption occurs if a real chemical bond is formed between the substrate and the adsorbate. Molecules may adsorb intact or dissociate on the surface. Catalytic reactions almost always involve the dissociation of at least one of the reacting molecules. In certain highly stable molecules, such as methane or ethane, chemisorption is not possible without the rupture of a C-H bond. Dissociation of molecules on metals leads to predominantly neutral fragments (homolytic bond splitting), whereas on oxides, the dissociation... 

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