Fischer-Tropsch synthesis: Synergistic effect of hybrid Pt-Cd additives on a 15%Co/Al₂O₃ catalyst

The study investigated a synergistic effect of the hybrid Pt-Cd additives on a cobalt catalyst. Adding 1%Cd to 0.5%Pt-15%Co/Al₂O₃ led to 90% activity loss and significantly increased CH₄ and CO₂ selectivities. HR-TEM/STEM micrographs revealed that a fraction of Cd nanoparticles deposited on large Co particles, resulting in the severe deactivation. More interestingly, the hybrid Cd-Pt additives were found to have a synergistic effect on the secondary reactions of 1-olefins; each modifier counteracted the other individual additive's role for the formation of olefins. For example, Cd suppressed the 1-olefin hydrogenation ability of Pt and Pt suppressed the 1-olefin isomerization ability of Cd. The XPS, TEM and NH₃-TPD studies revealed that the Pt-Cd dual additives provided unique electronic effect (e.g., Pt and Cd enhanced electronic backdonation and Pt blocked electron transfer), which improved 1-olefin selectivity and suppressed 2-olefin selectivity of the cobalt catalyst.