Separation of F-T Wax from Ultra-fine Iron Catalysts

Fischer- Tropsch Synthesis (FTS) is an established catalytic process for producing hydrocarbons and other chemicals from coal and natural gas. Still, many barriers exist for FTS to become an economical alternative for the production of hydrocarbon fuels. For coal-based FTS, the syngas produced typically has a lower H2/CO ratio as compared to that of natural gas. Thus, iron catalysts exhibit many advantages over other traditional FTS catalysts in terms of water gas shift activity, costs, and availability. Slurry-phase FTS is the preferred reaction medium since the process is highly exothermic. Consequently, heavy wax products must be separated from catalyst particles before being removed from the reactor system. Achieving an efficient wax product separation from iron-based catalysts is one of the most challenging technical problems associated with slurry-phase FTS. The separation problem is further compounded by catalyst particle attrition and the formation of ultra-fine carbide particles. Numerous separation processes have been proposed in the literature based on a variety of filtration media along with washing/cleaning techniques. Some limited fundamental studies have shown that attrition resistance of iron-based catalysts depends on the type of activation the catalyst receives. However, these studies have not attempted to correlate the change in filtration properties of catalyst slurries with physical and chemical changes of the particles under real-world conditions. Therefore, in the proposed research program, we intend to "bridge" the gap between industrial filtration techniques and fundamental chemical/physical changes of iron-based catalyst particles under FTS conditions.