2,6-Lutidine adsorbed IR spectroscopy has been employed to study the property of acidic sites on MoO3 and Pt/MoO3. The results showed that both catalysts possess doublet adsorption bands at 1605+1585 cm(-1), ascribed to Lewis acid sites, and duo-doublet bands at 1660+1650 and 1640+1630 cm(-1), ascribed to hydroxyl groups: these indicate an OH defect structure of MoO3 and Mo-OH Bronsted acidic sites. All Bronsted acid sites were strong enough to retain outgassing at 473 K, while a considerable number of relatively weak and medium acid sites as well as strong Lewis acid sites existed. The addition of Pt slightly altered the ratio of Lewis/Brtinsted acid sites and distribution of Lewis acid sites. The XRD result confirmed the formation of molybdenum oxyhydride (MoOx)(-)(H-y)(+) on the hydrogen treated Pt/MoO3, whereas the hydrogen adsorption on 2,6-luddine pre-adsorbed catalysts showed the formation of protonic acid sites over Pt/MoO3. These results strongly suggested that the interaction of molecular hydrogen with Pt/MoO3 formed acidic Bronsted (MoOx)-(Hy)(+) via a hydrogen spillover mechanism. In fact, no (MoOx)(-)(H-y)(+) and protonic acid sites were observed on Pt-free MoO3. The presence of (MoOx)(-)(H-y)(+) enhanced the activity of Pt/MoO3 in the cumene hydrocracking in which the rate conversion of cumene increased by about 30%, while the apparent activation energy decreased by approximately 28 kJ/mol. (C) 2013 Elsevier B.V. All rights reserved.