Acidic and Catalytic Properties of Niobium Pentaoxide

The surface acidic property of Nb2O5·nH2O and its catalytic activities for the isomerization of 1-butene, the polymerization of propylene and the dehydration of 2-butanol were examined. The activities were high on Nb2O5·nH2O evacuated at moderate temperatures(100–150 °C) in all of the reactions and decreased drastically on evacuation at higher temperatures (400–500 °C). The surface of Nb2O5·nH2O showed a strong acidic character (H0≤−5.6) even after heating in air at 100 °C, but the strong acid sites disappeared on heat treatment at higher temperatures. The active sites on the catalysts heat-treated at moderate temperatures were ascribed mainly to Brönsted acid sites on the basis of the IR study of adsorbed pyridine.