Carbon monolith supported Fe-Based catalyst Boosts olefins production performance of Fischer-Tropsch synthesis via enhanced Mass-Transfer effect

Even though the carbon-based Fischer-Tropsch synthesis (FTS) catalysts deliver excellent performance owing to the outstanding physicochemical property of carbon materials, the poor mechanical strength and difficulty in formability are the bottlenecks for their practical and industrial applications, especially in a fixed-bed reactor. To tackle this obstacle, we propose a stepwise heat treatment protocol to successfully fabricate a biomass-derived monolithic carbon material with favorable mechanical strength. The carbon monolith can be employed as promising Fe-based active sites carrier to boost the olefins production performance of FTS. Compared with the powdered counterpart under the same reaction conditions (260 °C, 3 MPa, CO:H₂ = 1:2, GHSV = 3000 mL g_cat⁻¹h⁻¹), the catalytic activity of the monolithic catalyst is significantly increased from 37.2 % to 64.3 % while maintaining the high selectivity of olefin products (68.1 %), therefore the maximum olefin space–time yield approaching to extremely high value of 666 mg g_Fe3O4^-1h⁻¹ (260 °C, 3 MPa, CO:H₂ = 1:2, GHSV = 6000 mL g_cat⁻¹h⁻¹). Multiple characterizations reveal that the formation of interconnected monolithic structure can be attributed to the dehydration-polymerization reaction between the biomass carbon and binder. Based on the heat and mass transfer simulations, it is obvious that the monolithic catalyst possesses superior mass and heat transfer performance and better reactants diffusion behaviors, which contribute to the formation of more χ-Fe₅C₂ active phase for C-O bond activation and C-C bond coupling. This work will shed new light on the rational design of highly efficient monolithic FTS catalyst with remarkable strength for practical application at large scale.