A series of Pd catalyst supported on tungstated metal oxides (Pd/W-MOx) were prepared and applied for pyrene hydrogenation, and the role of acid sites of supports was investigated. Among Pd/W-MOx catalysts, Pd/W-TiO2 showed the highest activity which was comparable to those of Pd/BEA. Pd/Y and Pd/SiO2-Al2O3. As for the Pd catalysts supported on metal oxides without tungstate (Pd/MOx), the hydrogenation activity became higher with the increase in the acid amount of supports measured by calorimetric measurement of ammonia adsorption. The important role of acid sites on hydrogenation activity was demonstrated. On the other hand, the hydrogenation activity of Pd/W-MOx catalysts was not correlated to the acid amount of supports measured by ammonia adsorption. On-site generation of protonic acid on tungstated metal oxide supports was estimated from kinetic analysis of reduced W species in the presence of hydrogen by in situ UV-visible measurement. From a good correlation between the kinetic parameters of on-site protonic acid formation and the hydrogenation activity, the important role of protonic acid formation on tungstated metal oxide supports was clarified. (C) 2010 Elsevier B.V. All rights reserved.