Synergistic effect of K and Zn on Fe-based catalysts for efficient CO hydrogenation.

Excessive emission of CO into the atmosphere has severely impacted the global ecological environment. Converting CO into valuable chemicals and fuels is of great significance for sustainable development. However, low activity and undesirable selectivity often result from the inherent inertness of CO. Herein, K- or/and Zn-modified Fe-based catalysts were prepared by an incipient-wetness impregnation method for CO hydrogenation a cascade reaction. The results indicate that K species exist as KO while Zn species exist as ZnFeO. In the CO hydrogenation pathway, KO facilitates the adsorption of CO and restrains the adsorption of H, accelerating the transformation of CO into C-C olefins rather than paraffins while Zn species promote the dispersion of Fe species, leading to improved activity. Synergistically, a K- and Zn-modified Fe-based catalyst (2Zn-10K-Fe/Al) shows excellent catalytic CO hydrogenation activity, achieving a CO conversion of 77% which is 1.8 times that (42%) of the unmodified Fe-based catalyst (Fe/Al). Our catalyst also shows a significantly promoted selectivity to C-C olefins of 17% in comparison with the Fe/Al catalyst (0%). It is envisioned that such a binary effect of elements might contribute to the low-cost and industrial production of Fe-based catalysts for selective CO conversion.