The oxidation activity and acid-base properties of SnO2-based binary catalysts: I. The SnO2V2O5 system

The amounts of both the acidic and basic sites of a series of SnO₂V₂O₅ catalysts with different compositions were measured by studying the adsorption of the basic and acidic molecules in the gas phase, using both the static and pulse methods. The acidities of the catalysts are fairly low in the low range of V₂O₅ content (V < 20 atom%); the acidity per unit of weight shows a maximum at about V = 40–50 atom%, but the acidity per unit of surface area increases continuously with the V₂O₅ content. On the other hand, the pure SnO₂ has a fair basicity, and the introduction of a smal amount of V₂O₅ (V = 2–20 atom%) to SnO₂ remarkably enhances the basicity. It can be said that the SnO₂-rich (V < 20 atom%) catalysts are basic, while the V₂O₅-rich catalysts are acidic. The vapor-phase oxidation of 1-butene and butadiene, the isomerization of 1-butene, and the dehydration and dehydrogenation of isopropyl alcohol (IPA) were carried out in the presence of an excess of air, and the relationship between the catalytic behavior and the acid-base properties was investigated. It was concluded that the activities and selectivities can be relatively well explained by the acid-base properties between the catalyst and the reactant.