FeMn@HZSM-5 capsule catalyst for light olefins direct synthesis via Fischer-Tropsch synthesis: Studies on depressing the CO₂ formation

For Fe-based Fischer-Tropsch synthesis catalyst, how to decrease CO₂ formation is a big challenge. In this work, a capsule catalyst (FeMn@HZSM-5) with FeMn as core and HZSM-5 as shell was prepared and used for Fischer-Tropsch to olefins (FTO) reaction, compared with bare FeMn catalyst and several hybrid catalysts by physically mixing FeMn and HZSM-5 in different ways. Among these catalysts, the FeMn@HZSM-5 capsule catalyst showed the best catalytic performance with the highest light olefins selectivity and the lowest CO₂ selectivity. Compared with FeMn catalyst, the CO₂ selectivity of FeMn@HZSM-5 catalyst decreased more than 10%. However, the CO₂ selectivity of other physically mixing catalysts was similar to that of bare FeMn catalyst, indicating that randomly adding HZSM-5 had no effect on depressing the CO₂ formation. Benefiting from the HZSM-5 shell, the FeMn@HZSM-5 capsule catalyst could effectively affect the diffusion of H₂O and thus suppress the water-gas shift reaction in FTO reaction.