Effect of palladium on iron Fischer-Tropsch synthesis catalysts

Studies were conducted to investigate the effect of Pd on the Fischer-Tropsch Synthesis (FTS) selectivity, activity and kinetics as well as on the water-gas shift activity of an iron catalyst. Two palladium promoted catalysts (Pd0.002/Fe100 and Pd0.005/Fe100) were prepared from a base Fe100/Si5.1 (atomic ratio) catalyst. Results of FTS over the two palladium promoted catalysts were compared to those obtained from the K/Fe/Si base catalyst and a Cu/K/Fe/Si catalyst. The results indicate that Pd enhanced the FT activity while the selectivity for CO2 and CH4 changed little compared to the results for the base catalyst and the Cu promoted catalyst. Palladium promotion had a negative effect on the C-2-C-4 olefin to paraffin ratio. Pd promotion led to a higher WGS rate than the other two catalysts at high syngas conversions. A higher WGS rate compared to the FTS rate was obtained only for the Pd promoted catalysts. The FTS rate constant for the Pd promoted catalyst is higher than the base catalyst but lower than for the Cu promoted catalyst.