Ru/Mn/Al2O3 and Ru/Al2O3 catalysts, which prepared with various ruthenium precursors into impregnation method, were investigated for Fischer-Tropsch (FT) synthesis in a continuous stirred tank reactor; and the catalysts were characterized by H2-chemisorption, TPR, XRD, TEM and XPS. On the basis of Ru/Mn/Al2O3 catalysts, Ru(Cl)/Mn/Al2O3 prepared with ruthenium chloride exhibited much higher catalytic activity and stability than those on Ru(A)/Mn/Al2O3 and Ru(N)/Mn/Al2O3, which were prepared with ruthenium acetylacetonate and ruthenium nitrosyl nitrate precursors. The order of the CO conversion was Ru(Cl)/Mn/Al2O3 Ru(A)/Mn/Al2O3 Ru(N)/Mn/Al2O3. This order was also agreed with the order of CO conversion on Ru/Al2O3 in various ruthenium precursors. One explanation is in characterization results that the particle size of Ru and the pore diameter of the support such as 8 nm can be performed to influence high FT activity. On the other hand, over Ru(Cl)/Mn/Al2O3 and Ru(Cl)/Al2O3 catalysts, lower activity and higher deactivation rate with reaction time on Ru(Cl)/Al2O3 were clearly observed, where Ru(Cl)/Mn/Al2O3 showed high resistance to catalyst deactivation. In this observation, manganese chloride can be formed by removing chlorine atoms from ruthenium chloride, thus increasing the concentration of metallic Ru active species on the catalyst surface and with inhibiting catalyst deactivation.

A series of Ru/Mn/Al2O3 catalysts with different concentrations of manganese were investigated on catalyst characterization and activity for Fischer-Tropsch synthesis in a continuous stirred tank reactor. The Ru/Al2O3 and Ru/MnO showed low catalytic activity and deactivation rate was clearly observed at 493 K and 2 MPa. On the other hand, the addition of small amount of manganese in Ru/Mn/Al2O3 (Mn/Al 1/19) improved catalytic performance for Fischer-Tropsch synthesis. In an investigation, we observed a pressure effect between 1 and 6 MPa over Ru/Mn/Al2O3, and this catalyst showed high CO conversion and high stability with time on stream at 4 and 6 MPa. At 4 MPa, CO conversion was estimated to be about 95%. The catalysts were characterized by BET surface area, BJH porosity, CO chemisorption, XRD, TPR, TEM and XPS. Characterization results suggest that a suitable ratio of manganese to aluminum in Ru/Mn/Al2O3 increases the concentration of active ruthenium metals and it can be associated with the formation of manganese chloride at the catalyst surface.

The effects of manganese salts on Ru/Mn/Al2O3 catalysts prepared by the impregnation method for FischerTropsch synthesis were investigated. The catalysts were named Ru/Mn(N)/Al2O3, Ru/Mn(A)/Al2O3, Ru/Mn(S)/ Al2O3 and Ru/Mn(Cl)/Al2O3 according to the manganese nitrate, manganese acetate, manganese sulfate and manganese chloride salts. In the slurry phase Fischer-Tropsch reaction, Ru/Mn(N)/Al2O3 showed high and stable catalytic performance for CO conversion and space time yield under the reaction conditions, whereas other catalysts were deactivated. The order of catalytic performance was Ru/Mn(N)/Al2O3Ru/Mn(A)/Al2O3 Ru/ Mn(Cl)/Al2O3 Ru/Mn(S)/Al2O3. The catalyst porosity, CO chemisorption, XRD, TEM, TPR and XPS were observed, which indicated that the similar size of Ru particle and pore diameter at 8 nm on Ru/Mn(N)/Al2O3 may increase the number of active Ru atoms on the catalyst surface due to the formation of manganese chloride, resulting in the high catalytic activity and stability for Fischer-Tropsch synthesis.