The properties of molybdenum catalysts prepared by temperature-programmed decomposition Of Mo(CO)(6) adsorbed on de-aluminated Y zeolites were studied as a function of the silica-alumina ratios and sodium contents of the zeolite supports. The effect of the gas stream during activation was also studied. The catalysts were tested in benzene hydrogenation, and the catalysts and zeolite supports were characterized by several methods, including temperature-programmed decomposition of adsorbed n-propylamine, N-2 adsorption and Si-29 NMR. The highest hydrogenation activity was obtained with the catalysts activated under a 20% (v/v) CH4/H-2 gas mixture using temperature programming up to 923 K. Activity increased with decreasing protonic acidity of the zeolite support. Catalyst stability increased in the same direction due to production of alkylation products in the more acidic zeolites. (c) 2006 Elsevier B.V. All rights reserved.