Nano-ZSM-5-supported cobalt for the production of liquid fuel in Fischer-Tropsch synthesis: Effect of preparation method and reaction temperature

摘要

ZSM-5 zeolite is usually used to modify the product selectivity for Fischer-Tropsch synthesis (FTS). Here, we prepared a nano-ZSM-5 zeolite with a particle size of 80 nm. This zeolite was used as a support to prepare bifunctional Co-based FTS catalysts by incipient wetness impregnation [using water as a solvent (W-Co/H-ZSM-5) or alcohol as a solvent (A-Co/H-ZSM-5)] and an ultrasound-assisted impregnation method (U-Co/H-ZSM-5). These catalysts were characterized by X-ray diffraction (XRD), N-2-physical absorption, H-2 temperature-programmed reduction (H-2-TPR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The FTS catalytic performances of all catalysts were compared in a fixed-bed reactor. Characterization data revealed that the U-Co/H-ZSM-5 catalyst had the best cobalt dispersion, resulting in the most stable CO conversion. Moreover, the nanoscale relationship between the activity and acid sites enhances the hydrocracking ability, increasing the liquid fuel selectivity from 49.7% to 67.8% (no C20+ product was detected for U-Co/H-ZSM-5) for a reaction at 503 K. In addition, the CH4 selectivity increases as the reaction temperature increases from 483 K to 513 K, which is beneficial for producing liquid fuel products (67.8%) at a reaction temperature of 503 K.