Effect of Re Content over Fe-Based Catalysts in Hydrocarbon Production from CO ₂ -FT Reaction

The present work reports Mg-promoted Re/Fe catalysts supported on activated carbon for CO2-FT, evaluating the effect of the Re/Fe ratio. The catalysts were obtained by impregnation and characterized by N2-sorption, XRD, TPR, and XPS. Textural data indicate progressive porosity loss at high Re loading. XRD reveals Re, ReOx, and Fe phases, with angle shifts consistent with Re–Fe solid solution formation in fresh catalysts and lattice expansion/phase segregation after reaction. XPS showed that Re promotes surface Fe reduction/carburization (Fe0/Fe2+), while Re speciation dynamically evolves under reaction, with an increase in highly oxidized Re7+ after time on stream. The series shows a synergistic effect of activity and product selectivity on Re content. The Mg–Re/Fe-25% catalyst exhibits the highest selectivity toward hydrocarbon C2+ of 70% at 30% conversion and restrained CH4 formation while maintaining stable operation for >80 h. Comparison against a physical mixture of monometallic Fe and Re confirms that intimate Fe–Re interactions are required to promote FT pathways. Overall, the controlled incorporation of Re stabilizes reduced/carbide Fe species and tunes the Fe electronic structure, offering a rational handle to optimize CO2-FT performance and catalyst stability.