Effect of crystal phase and pore structure of Al2O3 support was examined in order to improve the activity of Co/Al2O3 catalysts for FT synthesis. Total 18 kinds of Al2O3 supports having different crystal phase and pore structures were prepared by the calcination of commercial boehmite and gibbsite under various conditions. Cobalt was loaded on these Al2O3 supports by the impregnation, drying and calcination. Activity of Co/Al2O3 catalyst for FT synthesis was evaluated with a continuously stirred tank reactor. Structure of Co particles and activity of Co/Al2O3 catalysts strongly depended on the pore structure (i.e. surface area and pore size) of Al2O3 support rather than the crystal phase. Among the examined samples, the highest activity was obtained over the catalyst, which was prepared from theta-Al2O3 having the moderate surface area (84 m(2) g(-1)). When Al2O3 supports having the moderate surface area were used, the formation of Co particles having high dispersion and relatively uniform size was promoted by pores of suitable size and led to the enhancement of overall catalytic activity. (C) 2014 Elsevier B.V. All rights reserved.