The Oxidation Activity and Acid-base Properties of Mixed Oxide Catalysts Containing Titania. I. The TiO2–MoO3 and TiO2–V2O5 Systems

Abstract

Abstract The amounts of both the acidic and basic sites of two series of catalysts, TiO2–MoO3 and TiO2–V2O5, 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 acidity of TiO2–MoO3 catalysts is very high at Mo=40–60 atom%, though those of the TiO2-rich (Mo<30 atom%) and MoO3-rich (Mo>80 atom%) catalysts are fairly low. The acidity of the TiO2–V2O5 increases steadily with the V2O5 content. The basicity of the catalysts is remarkably enhanced by the introduction of a small amount of MoO3 or V2O5. It can be said that the catalysts are basic at Mo<20 atom% or V<10 atom%, while the MoO3-rich or V2O5-rich catalysts are acidic. The vapor-phase oxidation of 1-butene, butadiene,and acetic acid, the dehydration and dehydrogenation of isopropyl alcohol (IRA), and the isomerization of 1-butene 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.