Redox properties, of metal oxides

Acid-Base Properties of Metal Oxides 617 Redox Property of Metal Oxides 619 Synthesis 619 Sol-Gel Technique 620... 

Redox Properties of Metal Oxides and Catal3iic Implications... 

It was found that acidic or basic properties of metal oxides are not directly connected to their hydrogenolytic power, but redox properties seem to play a more important role.19... 

A unique property of metal oxides is their ability to also exchange O ions with adsorbates this property makes them very useful as partial oxidation catalysts. Such ion transport is a type of redox reaction in that charge (here in the form of an 0 ion) is really transferred from the substrate to the adsorbate. A simple example of a redox reaction with O ion transfer is the oxidation of CO ... 

Formic acid is a popular molecule for probing the catalytic properties of metal oxides [23-28], The selectivity of its decomposition has frequently been used as a measure of the acid-base properties of oxides. This is a tempting generalization to make oxides that produce dehydration products (H2O and CO) are described as acidic oxides, while their basic counterparts produce dehydrogenation products (H2 + CO2). It has been shown that in many cases the product selectivity is better connected to the surface redox behavior of the oxide [29], Thus, more reducible surfaces produce higher yields of CO2, Consequently, particular attention has been paid in surface science studies to the interaction between adsorbed formate ions (the primary reaction intermediate) and surface metal cations, as well as to the participation of lattice oxygen anions in the surface reaction mechanism,... 

The high selectivity of RLH-catalysts to olefins is a result of a definite combination of surface oxygen state, oxygen / metal cations ratio, redox properties of metal cations and acidity-basicity balance. Further studies are needed in order to understand the role of the support and the proper functioning of RE-Alkali-Halogen systems in oxidation of low paraffins. 

Finally some remarks will be included on the redox properties of metal phthalocyanines (V Pht) because a comparison with the metallo-porphyrins yields some information as to how the different metal oxidation states are stabilized in the porphyrin cavity. Closely related porphyrins are the tetrabenzoporphyrins and the ms-tetraaza-porphy-rins, which produce absorption spectra similar to those of phthalocyanines. 

The ease of the redox reactions of metal cations in the framework suggests that metal cations can be easily substituted into the framework of aluminophosphate molecular sieves. The changes in the coordination of Al ions in the framework by the adsorption of some gases such as H2 have also been reported by some researchers. This has not been observed for aluminosilicate zeolites. Although no investigation has been performed on the influence of the framework environment on the catalytic properties of aluminophosphate molecular sieves, there is a possibility that the restricted redox properties of metal cations in the framework catalyze reactions which proceed over free metal cations, as with oxides or ion-exchanged zeolites. 

Electrochemical reactions that lead to a degradation of the metal-polymer interface are influenced by the following properties the electron transfer properties at the interface, the redox properties of the oxide between the metal and the polymer and the chemical stability of the interface with respect to those species, which are formed during the electron transfer reaction. 

Oxidation state is correlated with the redox properties of metal ions. Thus, the metals in the highest oxidation state are oxidizing agents, whereas the metals in the lowest oxidation state are reducing agents. Between these extreme situations, the metals in intermediate oxidation states are redox ampholytes. 

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