Fischer–Tropsch synthesis (FTS) for the co-production of C 2 –C 4 olefins and clean fuels such as gasoline and middle distillate from syngas was investigated on four different iron-based catalysts in a fixed-bed and a bubbling fluidized-bed reactor. The catalysts were prepared by wet-impregnation using the Al 2 O 3 , SiO 2 and iron ore (FeO x ) supports with the active components of Fe, K and (or) Cu, and each K/FeCuAlO x catalyst was prepared by a co-precipitation method. Except for the catalyst impregnated on SiO 2 , CO conversion of the other catalysts is similar regardless of the type of reactor. However, the yield of light olefins in the range of C 2 –C 4 hydrocarbons and clean fuels is closely related to the formation of active iron carbide species and to surface acidity. The impregnated K/FeO x catalyst is found to be one of the promising catalysts to be applied in a bubbling fluidized-bed reactor for middle temperature FTS reaction due to its high resistance to catalyst attrition with a high catalytic performance.