(56d) Production of Middle Distillate Range Transportation Fuels From Synthesis Gas Using Fischer Tropsch Synthesis Technology Under Supercritical Phase Conditions

Fischer-Tropsch (FT) synthesis involves surface catalyzed polymerization reactions that inherently yield a high selectivity towards methane and a broad product distribution of gaseous light products, middle distillate hydrocarbons (olefins + paraffins), and heavy wax, as well as CO₂ and water.  Subsequent product upgrading via catalytic oligomerization and hydrocracking/isomerization can be employed to convert light olefin FT hydrocarbons into middle distillate range liquids, while also converting the long-chain hydrocarbons of heavy wax into fuel range products.  This results in a reduction in olefin selectivity and an enhancement of cold-flow properties. 

In an effort to further direct the FT product distribution towards middle distillate transportation fuel range products, we have undertaken a series of experiments where we have sequentially incorporated catalytic oligomerization and hydrocracking/isomerization stages subsequent to FT in single pass operation.  Moreover, we have utilized the enhanced heat transfer properties of supercritical fluid media in the FT and subsequent upgrading stages to reduce the selectivity towards CH₄ and CO₂.  Moreover, the use the supercritical solvent media provides prolonged catalyst life and activity maintenance.   In particular, this study involves a systematic investigation into the influence of the supercritical fluid reaction medium on the overall product distribution and selectivity towards fuel range products.