FeOx clusters confined in ZSM-5 as a high-performance catalyst for Fischer-Tropsch synthesis of lower hydrocarbons

Abstract

Under the dual pressures of oil depletion and low-carbon transition, Fischer-Tropsch synthesis (FTS) technology offers a viable option for producing high value-added lower (C₂-C₄) hydrocarbons from non-oil sources. However, conventional Fe-based catalysts often suffer from deactivation due to carbon deposition and sintering. Here, we report a unique Fe-ZSM-5 catalyst synthesized by doping Fe into ZSM-5, which demonstrates excellent FTS catalytic performance. During high-temperature template removal, Fe species migrated from the zeolite framework to form highly dispersed FeO_x clusters (∼2 nm). Upon treatment by syngas, these FeO_x clusters aggregate to form uniformly small-sized Fe₅C₂@C core-shell particles distributed on ZSM-5 support. The confinement effect of the inter-crystalline structure effectively prevents the sintering of Fe₅C₂. The smaller Fe₅C₂ particles exhibit controlled CO dissociation, reducing the concentration of activated carbon species (C*), and the carbon shells (∼6.5 nm) limit the departure of C*, effectively suppressing carbon deposition. This unique structure enables stable catalytic activity for over 100 hours with maintained product selectivity. The Fe-ZSM-5 catalyst achieved a C₂-C₄ hydrocarbons selectivity of 54.52 %, nearing the 56 % theoretical limit of the Anderson-Schulz-Flory (ASF) distribution. Additionally, the hydrophobic carbon shell prevents excessive oxidation of Fe₅C₂, reducing CO₂ selectivity by ∼56 % compared to conventional Fe/ZSM-5 catalysts, significantly enhancing atomic utilization efficiency and aligning with the principles of green development.