Increasing Liquid Fuels Selectivity in Fisher-Tropsch Synthesis From CO2-Rich Syngas

Fischer-Tropsch (FT) synthesis is a classic polymerization reaction in which a mixture of hydrogen and carbon monoxide (syngas) is converted to hydrocarbons and liquid fuels in presence of a metallic catalyst. FT synthesis could be considered as a promising technology to produce clean liquid fuels since it is able to match with different feedstocks including coal, natural gas, and biomass. While natural gas- and coal-based FT plants have already become a matured technology and been operated around the world, biomass-based plants are still under study and development. The ideal H₂/CO ratio of syngas entering a FT reactor is about 2.1. However, this ratio for the syngas derived from a biomass gasification reactor is often around 1. Such syngas usually contains significant amount of CO₂. Typical FT catalysts and processes cannot efficiently utilize CO₂. In this study, we have examined the possibility of utilizing CO₂ in two different feedstock: CO₂/H₂ and CO₂/CO/H₂. Performance and hydrocarbon distribution of different cobalt and iron based FT catalysts have been examined under a variety of FT synthesis conditions to study the effects of CO₂ presence in syngas feedstock on the efficiency and selectivity of a FT process and possible conditions for utilizing CO₂ in hydrocarbon production.