The chemisorption and hydrogenating properties of Ni/SiO2 catalysts prepared by the hydrazine method then calcined at 400 degrees C with various times were investigated. Metal dispersion and activity in benzene hydrogenation increased with increasing calcination time whereas desorbed amounts of hydrogen significantly decreased. Dilution of a calcined sample by the support led to a sharp increase of both hydrogen storage by the support and catalytic activity. Metal dispersion and hydrogen storage capacity influenced the reaction mechanisms of hydrogenation of benzene which, therefore, is believed to occur on the metal phase or/and on the support by the hydrogen spillover mechanism. The metal active phase would be composed of an ensemble of metallic and oxidized nickel species. (C) 2016 Elsevier B.V. All rights reserved.