Fischer–Tropsch Synthesis at High Conversions on Al2O3-Supported Co Catalysts with Different H2/CO Levels

Fischer-Tropsch experiments with different H2/CO ratios at high CO conversions have been carried out over an alumina-supported 20wt%Co-0.5wt%Re catalyst in a stainless steel fixed-bed reactor at 210 oC and 20 bar and with H2/CO ratios between 1.04 and 2.56. The results indicate that for H2/CO ratios above 2.1, CO conversion levels up to at least 85% can be obtained without significant short-term deactivation or loss of selectivity towards heavier hydrocarbons. Except for very low conversion anomalies, the data collapse into a single trendline for selectivity to C5+ products versus average hydrogen partial pressure in the reactor irrespective of the H2/CO feed ratio. The present results are important for development of small scale biomass to liquids plant based on a once-through process concept in order to avoid recycle streams

Fischer-Tropsch conversion of biomass-derived synthesis gas to liquid fuels

Recent and ongoing research on Fischer-Tropsch catalysts for biomass conversion typically focus on the effects of impurities common in bio-derived synthesis gas, and also on the effect of different synthesis gas compositions expected from biomass gasifiers. Cobalt and iron catalysts share the sensitivity towards some, but not all of the impurities. The most profound difference is the strong negative effect of alkali, alkaline earth and nitrogen containing compounds on cobalt catalysts while these impurities have a negligible or no effect on iron catalysts. CO2 appears to mainly act as a diluent in cobalt-based processes while iron catalysts respond differently to this component depending on catalyst design. In particular, iron catalysts containing Al2O3 as a structural promoter display a high stability, C5+ selectivity and activity in CO2 rich synthesis gas