In the Fischer-Tropsch (FT) synthesis, the catalytic behavior of Co-loaded powdered oxidized diamond (O-Dia) catalyst having a surface area of 24 m(2)/g was examined. The catalytic activity of 9 wt% Co-loaded oxidized diamond catalyst exhibited a high CO conversion of 44.5% at 250 degrees C with a total pressure of 1.0 MPa containing 1:2 CO and H-2 mixed gas, and a space velocity of 4500 h(-1). This conversion is much higher than that of Co-loaded SiO2 catalyst of two different surface areas, where CO conversions of 38.4% and 12.2% were obtained for SiO2 having a surface area of 190 m(2)/g and 12 m(2)/g, respectively. The effect of cobalt precursor salt was examined, and an increased CO conversion was obtained with the use of cobalt acetate as a source of Co. A much higher dispersion of Co with the use of cobalt acetate was observed by temperature-programmed reduction, CO adsorption, and TEM observations. A weaker interaction between the O-Dia surface and cobalt oxide seems to contribute to higher catalytic activity for the FT synthesis. (C) 2011 Elsevier Ltd. All rights reserved.