Effect of Mn addition on activity and resistance to catalyst deactivation for Fischer–Tropsch synthesis over Ru/Al2O3 and Ru/SiO2 catalysts

The effect of Mn addition to γ-Al2O3, α-Al2O3 and SiO2 supported Ru catalysts was investigated on catalytic activity, stability and selectivity in slurry phase Fischer–Tropsch reaction under pressurized conditions. At 493 K and 2.0 MPa, Ru/γ-Al2O3 and Ru/Mn/γ-Al2O3 exhibited much higher CO conversion, C5+ selectivity and carbon chain growth probability than α-Al2O3and SiO2 supported catalysts. From the comparison between Ru/γ-Al2O3 and Ru/Mn/γ-Al2O3, Ru/γ-Al2O3 was deactivated with time on stream; while Ru/Mn/γ-Al2O3 showed stable activity and the deactivation rate was negligible. On the other hand, the deactivation was clearly observed over α-Al2O3 and SiO2 supported catalysts. From XRD and TEM results, moderate particle size of ruthenium on γ-Al2O3 was found to be more active than highly dispersed ruthenium particles on α-Al2O3 and SiO2 supports. The effect of manganese addition would be associated with both the enhancement of surface concentration of ruthenium and a predominant interaction with surface chlorine over ruthenium, as estimated by XPS measurements.