Microstructured Al-fiber@meso-Al2O3@Fe-Mn-K Fischer-Tropsch catalyst for lower olefins

A thin‐sheet Al‐fiber@meso‐Al2O3@Fe‐Mn‐K catalyst is developed for the mass/heat‐transfer limited Fischer–Tropsch synthesis to lower olefins (FTO), delivering a high iron time yield of 206.9 µmolCO gFe−1 s−1 at 90% CO conversion with 40% selectivity to C2‐C4 olefins under optimal reaction conditions (350°C, 4.0 MPa, 10,000 mL/(g·h)). A microfibrous structure consisting of 10 vol % 60‐µm Al‐fiber and 90 vol % voidage undergoes a steam‐only‐oxidation and calcination to create 0.6 µm mesoporous γ‐Al2O3 shell along with the Al‐fiber core. Active components of Fe and Mn as well as additives (K, Mg, or Zr) are then placed into the pore surface of γ‐Al2O3 shell of the Al‐fiber@meso‐Al2O3 composite by incipient wetness impregnation method. Neither Mg‐modified nor Zr‐modified structured catalyst yields better FTO results than K‐modified one, because of their lower reducibility, poorer carbonization property, and fewer basicity. The favorable heat/mass‐transfer characteristics of this new approach are also discussed. © 2015 American Institute of Chemical Engineers AIChE J, 62: 742–752, 2016