Effects of Ruthenium Precursors on Ru/Mn/Al2O3 and Ru/Al2O3 Catalysts for Fischer-Tropsch Synthesis

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 H-2-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.