A Case Study Vanadia Catalysts

It is known that catalytic activity in selective oxidation of hydrocarbons can be related to the co-operative action of an oxidizing function and an acidic function. From this perspective, the determination of both the redox and the acidic 

NH3 adsorption calorimetry experiments performed on bulk V2O5 indicated a weak acidity, with an initial heat of adsorption of 70 kj moT and a large heterogeneity [125]. 

Regular pulses of pure ethane on bulk V2O5 maintained at 823 K in a microcalorimeter linked to a gas chromatograph provided kinetic data of theoretical significance, as weU as an insight into the mechanism of the reduction process. The results of this work carried out using mainly calorimetric techniques led to the conclusion that diffusion of oxygen from the bulk is predominant in the selective oxidation of ethane and that the redox process plays a more important role than the acidic sites in the case of unsupported vanadium pentoxide. 

Interaction with the support was enhanced after catalytic reaction, as indicated by the detection of new strong Lewis acid sites by DRIFT spectroscopy measure- 

The acid-base properties of V2O5/7-AI2O3 catalysts prepared by the impregnation method have been characterized by ammonia, pyridine and sulfur dioxide adsorption microcalorimetry. Sulfur dioxide adsorption made it possible to differentiate a vanadate layer from free alumina. 

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