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

摘要

The effect of Mn addition to gamma-Al2O3,alpha-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/gamma-Al2O3 and Ru/Mn/y-Al2O3 exhibited much higher CO conversion,C_5~+ selectivity and carbon chain growth probability than alpha-Al2O3and SiO2 supported catalysts.From the comparison between Ru/gamma-Al2O3 and Ru/Mn/gamma-Al2O3,Ru/gamma-Al2O3 was deactivated with time on stream;while Ru/Mn/gamma-Al2O3 showed stable activity and the deactivation rate was negligible.On the other hand,the deactivation was clearly observed over alpha-Al2O3 and SiO2 supported catalysts.From XRD and TEM results,moderate particle size of ruthenium on gamma-Al2O3 was found to be more active than highly dispersed ruthenium particles on alpha-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.