The nickel-niobia-silica interactions at low nickel contents

Nickel was impregnated in two Nb2O5/SiO2 samples. The first one contained s mall crystallites of niobia dispersed over silica and the second one a niob ia monolayer distributed quite uniformly over the silica substrate. These s ystems were submitted to different treatments (calcination and water vapor) in order to obtain different interactions between the nickel and niobia. A preferential interaction of the nickel with niobia was observed in both ni obia-silica Samples. The hydrogenation of benzene and dehydrogenation of cy clohexane were used to characterize the reduced surface nickel. Suppression in the catalytic activity was observed due to a strong metal-support inter action (SMSI) and nickel niobate formation. The extension of SMSI and nicke l niobate formation depend on the niobia-silica interactions, which are a f unction of sample preparation and treatment. (C)2000 Elsevier Science B.V. All rights reserved.