Na-loaded MoO3 was reduced with H-2 in the presence of Pt, and its catalytic activity for heptane isomerization was studied. The isomerization activity decreased abruptly with increasing Na loading. The same tendency was observed in the dehydration of 2-propanol. In contrast, the catalytic activity for cyclohexene hydrogenation was improved by increasing amounts of Na. The physical properties of the H-2-reduced catalysts, such as the surface area and the valence of Mo, were changed very little by the Na content. The isomerization and dehydration activities were related to the concentration of acid sites, which was determined from NH3-TPD. Thus, the isomerization reaction of heptane over H-2-reduced Pt/MoO3 is concluded to occur due to the existence of acid sites. (c) 2006 Elsevier Inc. All rights reserved.