Improved Fischer-Tropsch synthesis was carried out over Ru, Ni promoted Co/HZSM-5 catalysts to investigate the influence of promoters on the synthesis of gasoline-range hydrocarbons (GRHs, C-5-C-12 hydrocarbons). The catalysts were characterized by BET, XRD, TEM, H-2-TPR and NH3-TPD to clarify their physical and chemical properties. The catalytic activity for GRH production increased significantly with the addition of Ru or Ni promoter. CO conversion increased in the order Co/HZSM-5 < Ru-Co/HZSM-5 < Ni-Co/HZSM-5. Due to the higher reduction degree and weaker acid sites on the Ru-Co/HZSM-5 catalyst, CO conversion and GRH selectivity increased compared with the Co/HZSM-5 catalyst. Furthermore, the Ru-Co/HZSM-5 catalyst maintained its initial high activity and GRH selectivity after 150 h on stream at an optimum temperature of 540 K. The Ni-Co/HZSM-5 catalyst also showed high catalytic activity and GRH selectivity even at the relatively low temperature of 524 K. For all three catalysts, the content of iso-paraffin in the GRHs increased monotonically, almost linearly, with increase in temperature. For the NiCo/HZSM-5 catalyst in particular, the content of iso-paraffin in the GRHs increased very significantly. (C) 2013 Elsevier Ltd. All rights reserved.