Plug-Through Contactor Membranes (PCM) for the Fischer-Tropsch Synthesis
Specific features of the Fischer-Tropsch synthesis make crucial the following requirements to the reactor design, isothermal catalyst bed, high concentration of the catalyst in the reactor volume; high gas-liquid interface surface area, small effective size of catalyst grains, i.e., small effective diffusion length, and low pressure drop. The solution of the knotty problem of the trade between high concentration of the active component and mild mass-transfer limitations for the Fischer-Tropsch is suggested by using the heat-conductive plug-through contactor membranes (PCM). The PCM is a three-component mixture of a catalytically active substance, pore-producing agent, and reinforcing agent with a high heat conductivity which is sintered and reduced in H2 after mixing. The PCM is a three-modal porous structure, which is permeated by synthesis gas via the pores wider than 2-3 μm. PCM can combine high permeability (> 20 Darcy), high mechanical strength (> 20 kg/sq cm), and high heat-conductivity (> 4 w/(m K)). Therefore, it provides isothermicity and low pressure drop. The intense mass-transfer within transport pores, their high specific area (gas-liquid interface area), and small distance between two adjacent transport pores (effective diffusion length) weaken the mass-transfer constrains. This helps achieving high space-time yield of hydrocarbons (60-70 kg/cu m- hr at 0.1 MPa and 150-200 kg/cu m-hr at 2 MPa, 210°C, and high selectivity towards heavy hydrocarbons (α > 0.85) and olefins (propylene/propane ratio of 6:1-10:1). This is an abstract of a paper presented at the 227th ACS National Meeting (Anaheim, CA 3/28/2004-4/1/2004).