Heat of oxygen desorption

Measurements with a vacuum system of equilibrium oxygen partial pressures as a function of temperature indicate desorption energies. There is some difficulty in choosing a representative state of comparison. Generally, investigators evacuate at increased temperature for a long time. 

Of interest is the new flash technique applied by Halpern and Germain [153]. This technique reveals that mobile oxygen generally occurs in discrete binding states. The authors compared V205 and CuO with other catalysts mainly concerning total oxidation. 

Figueras et al. [Ill] emphasize the importance of the entropy of the oxygen bond, which can be considered as a measure of the surface mobility of oxygen. Unfortunately, their assumed positive correlation between entropy and selectivity is only based on two V2Os catalysts which differ with respect to the carrier (Si02 and A1203). 

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The most important properties used as a measure of the bonding strength are the heat of formation of the metal oxides, the heat of oxygen desorption, the reducibility of the metal oxide and the activation energy for isotope exchange between l802 in the gas phase and oxygen in the catalyst. 

Table 20.15 The OFe(OH)2 properties predicted via different quantum-chemical approaches Fe-O bond length, vibrational frequency, multiplet splitting and the heat of oxygen desorption, see Eq. 20.12...

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