Sulfur (H2S, COS), halide (NaCl and KCl) compounds), the halogenated acids (HX, X = Cl, Br or F) and hydrogen cyanide (HCN) are common impurities present in biomass-derived syngas. Investigating the effects of HX and HCN on Fischer-Tropsch synthesis (FTS) catalyst behavior is important for developing the biomass to liquid (BTL) process, with the aims of lowering gas purification costs and improving catalyst lifetimes. So far, few studies have examined the impacts of HX and HCN contaminants.  The current investigation was undertaken to explore the sensitivity of a 100Fe/5.1Si/2Cu/3K FTS catalyst to HX and HCN impurities in syngas under industrially relevant conditions using a 1-L slurry-phase reactor. HX concentrations less than 1.7 ppm and HCN concentrations less than 6.0 ppm in syngas did not significantly impact the Fe catalyst activity; 5 ppm HX in syngas impacted the initial deactivation rate, but the catalyst activity stabilized following that interval.  At higher levels of HX (i.e., 20 ppm and above), rapid deactivation was observed. By comparing the deactivation trends and calculating the impact of each contaminant molecule on the deactivation of Fe sites, the results suggest that the larger molecules have a greater impact on the deactivation rate, with the following trend being observed: Br > Cl > F. The Fe catalyst was also found to be more sensitive to HX poisons at low temperature, further suggesting an adsorptive mechanism for poisoning.

Effects of halogenated acids and hydrogen cyanide in syngas on a precipitated iron Fischer�Tropsch synthesis catalyst

248th National Meeting (2014)

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