Carbon Nanotubes–MnOx Nanocomposite as Support for Iron‐Based Catalysts for the Fischer–Tropsch Synthesis of Liquid Fuels

A facile one-pot hydrothermal method is developed to synthesize a series of carbon nanotubes–manganese oxide nanocomposites (CNTs–MnOx) with different morphologies and Mn valence states. These nanocomposite materials are then utilized as catalyst supports in iron-based Fischer–Tropsch synthesis (FTS) for the production of liquid fuels. Experimental results indicate that Fe/CNTs-K-190 (iron catalyst supported on the CNTs treated with KMnO4 at 190 °C) and Fe/CNTs-KU-190 (iron catalyst supported on the CNTs treated with KMnO4 and urea at 190 °C) display higher FTS activity than the Fe/CNTs-K-110 (iron catalyst supported on CNTs treated with KMnO4 at 110 °C) and Fe/CNTs-KU-110 (iron catalyst supported on CNTs treated with KMnO4 and urea at 110 °C). This might be due to the weak metal–support interaction and high MnO content, and the poorer stability than Fe/CNTs-K-110 and Fe/CNTs-KU-110 catalysts with nanosheet morphology might be related to the structural collapse of the nanocubes or nanorods due to MnO evolution during the FTS process. The CNTs–MnOx nanocomposite-supported iron FTS catalysts in particular display unparalleled high C5+ selectivity (over 90 %) and very low CH4 selectivity (below 4.6 %). The unique CNTs–MnOx nanocomposites may open a new window for the understanding, design, synthesis, and optimization of iron catalysts toward high-efficiency transport fuel production.