Effect of Re Content over Fe-Based Catalysts in Hydrocarbon Production from CO2-FT Reaction

Abstract

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 N-2-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 (Fe-0/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 C-2(+) 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.