The natural Na-type montmorillonite (Na-MMT) suspended in the 20 wt% HNO3 aqueous solution at concentrations between 2-20 wt.% was activated at 70-104 degrees C for a period, respectively. The thus obtained materials were abbreviated as acid-MMT-m-t/T, where m, t and Tare the concentration of Na-MMT suspension (wt.%), time (h), and temperature (degrees C) during the acid activation, respectively. The Co-Ru/acid-MMT (20 wt.% Co and 0.1 wt.% Ru) was prepared by the incipient impregnation method. The materials were characterized by XRD, FT-IR, XRF, N-2 adsorption-desorption at low temperature, H-2-TPR, H-2-TPD, oxygen titration, and NH3-TPD techniques. In comparison to the results of the Na-MMT, the structural, textural, and acidic properties of the acid-MMTs were clearly changed, the extent of which is strongly dependent on the acid activation conditions. For the first time, the acid-MMT with desired properties were obtained using a high ratio of Na-MMT suspension, such as 10 wt.%, leading to a significantly improved process efficiency of the acid activation. The structural and compositional changes of acid-MMTs gave significant impacts on the reduction behavior of Co-Ru/acid-MMT catalysts. Moreover, the addition of Ru to Co/acid-MMTs decreased the peak temperatures of the two-step reduction of Co3O4 to Co via the CoO intermediate, leading to an increased extent of reduction of cobalt. The catalysts were comparatively investigated for Fischer-Tropsch (FT) synthesis in a fixed-bed reactor under the conditions of H-2/CO = 2, W/F = 5.0 g . h . mol(-1), 235 degrees C, and 1.0 MPa. Results showed that the CO conversion was decreased in the order of Co-Ru/acid-MMT-2-12/104 > Co-Ru/acid-MMT-10-12/104 > Co-Ru/acid-MMT-20-12/104 >> Co-Ru/acid-MMT-2-12/70 > Co-Ru/acid-MMT-2-4/70 > Co/acid-MMT-2-4/70. Moreover, all of the Co-Ru/acid-MMT catalysts showed clearly higher selectivity of C-5-C-12 hydrocarbons and lower selectivity of C-21(+) hydrocarbons compared with Co/SiO2 catalyst. The Co-Ru/acid-MMT-2-12/70 showed about 46% C-5-C-12 selectivity at a reasonable CO conversion level. (C) 2014 Elsevier B.V. All rights reserved.