Fischer-Tropsch synthesis was conducted over carbon-supported iron catalysts at 260-280 degrees C and 2.0 MPa. Potassium addition enhances the selectivity to liquid hydrocarbons greatly. A high space time yield of total hydrocarbons of 450 g kg(-1) h(-1) was attained over K-promoted active carbon-supported catalyst. Ozone treatment of the active carbon surface is found to be effective for the catalyst durability. It is inferred that enlarged average pore diameter plays an important role for the stability by the smooth extraction of the waxy products. (C) 2013 Elsevier B.V. All rights reserved.