Mn effect and characterization on gamma-Al2O3-, alpha-Al2O3- and SiO2-supported Ru catalysts were investigated for Fischer-Tropsch synthesis under pressurized conditions. In the slurry phase FischeF-Tropsch reaction, gamma-Al2O3 catalysts showed higher performance on CO conversion and C-5(+) selectivity than alpha-Al2O3 and SiO2 catalysts. Moreover, Ru/Mn/gamma-Al2O3 exhibited high resistance to catalyst deactivation and other catalysts were deactivated during the reaction. From characterization results on XRD, TPR, TEM, XPS and pore distribution, Ru particles were clearly observed over the catalysts, and gamma-Al2O3 catalysts showed a moderate pore and particle size such as 8 nm, where alpha-Al2O3 and SiO2 showed highly dispersed ruthenium particles. The addition of Mn to gamma-Al2O3 enhanced the removal of chloride from RuCl3 which can lead to the formation of metallic Ru with moderate particle size, which would be an active site for Fischer-Tropsch reaction. Concomitantly, manganese chloride is formed. These schemes can be assigned to the stable nature of Ru/Mn/gamma-Al2O3 catalyst. (c) 2008 Elsevier B.V. All rights reserved.