A Monodisperse epsilon '-(CoxFe1-x)(2.2)C Bimetallic Carbide Catalyst for Direct Conversion of Syngas to Higher Alcohols

Higher alcohol synthesis (HAS) from syngas through non petroleum carbon resources is quite prospective but still challenging owing to the unsatisfactory selectivity and catalytic stability. Here, we proposed a monodisperse epsilon'-(CoxFe1-x)(2.2)C alloy carbide catalyst derived from CoxFe3-xO4 spinet oxide nanoparticles, which was applied in the HAS reaction. The Co/Fe molar ratio showed a significant impact on the evolution of active sites, and the catalyst with a Co/Fe molar ratio of 1/2 contained the highest epsilon'-(CoxFe1-x)(2.2)C content of 80.2%, which achieved the best selectivity and space time yield toward higher alcohols (HA) as high as 38.5% and 1.932 g g((Fe + Co))(-1) h(-1), outperforming most of the reported modified Fischer-Tropsch synthesis catalysts for HAS. Density functional theory calculations further confirmed that the formation of epsilon'-(CoxFe1-x)(2.2)C alloy carbide became more difficult when the Co/Fe ratio exceeds 1/2. It is demonstrated that the epsilon'-(CoxFe1-x)(2.2)C exhibited moderate bonding with CO, which is crucial for the balance between CO dissociation and CO insertion, thus increasing the HA selectivity. The Co1Fe2 catalyst with a robust CoFe alloy carbide structure exhibited stable catalytic performance for over 300 h because of the inhibition of phase separation and surface carbon deposition. These insights into the formation and properties of CoFe alloy carbide may provide possibilities for the development of bimetallic catalysts for HAS.

Automated summary

In this study, a monodisperse ε'-(CoxFe1-x)(2.2)C alloy carbide catalyst derived from CoxFe3-xO4 spinel oxide nanoparticles has been proposed for higher alcohol synthesis from syngas. The catalyst shows excellent selectivity and stability due to its alloy structure, which balances the CO dissociation and insertion reactions, and inhibits phase separation and surface carbon deposition, leading to superior catalytic performance.