Palladium species were loaded into mesoporous Beta zeolite (Beta-H), and transmission electron microscopy images showed that the Pd particles are located in both mesopores and micropores. As a model reaction, the deep hydrogenation of bulky aromatic pyrene showed that the Pd/Beta-H catalyst exhibits higher activity than Pd/Beta, Pd/Al-MCM-41, and Pd/gamma-Al2O3 catalysts. The superior performance of the Pd/Beta-H catalyst is attributed to its unique porous structure and acidity. The mesoporous volume in Beta-H (0.17 cm(3)/g) is greater than that of Beta (0.06 cm(3)/g), which is advantageous for adsorption and mass transport of pyrene over Pd/Beta-H catalyst. The amount of acidic sites is greater on Beta-H (480 mu mol/g) than on Al-MCM-41 (280 mu mol/g) and gamma-Al2O3 (220 mu mol/g), which also favors improved catalytic activity in hydrogenation of pyrene over Pd/Beta-H catalyst. (C) 2007 Elsevier Inc. All rights reserved.