CO hydrogenation over Fe-promoted Rh–Mn–Li/SiO2 catalyst: The effect of sequences for introducing the Fe promoter

• Sequential and co-impregnation methods were employed for the preparation.
• The interaction of Rh and Fe changed by different impregnation sequences.
• FeOx achieved closer contacts with the RhOx as the Fe layer in the Rh and Mn below.
• The closer interaction could lead to an increase in the Rh–Fe interface.
• The increase in Rh–Fe interface is conducive to synthesize C2 oxygenates.

The effects of different impregnation sequences for the precursors of iron and other metals (Rh, Mn, Li) on the catalytic properties of Fe-promoted Rh–Mn–Li/SiO2 catalysts for the synthesis of C2+ oxygenates were investigated. The means of N2 adsorption–desorption, XRD, H2-TPR, in-situ FT-IR, and TPSR were used to characterize the physics-chemical properties of the catalysts. The results showed that when the iron was impregnated and calcined first followed by Rh–Mn–Li impregnation, it would availably inhibit the reduction of Rh and Mn oxides; however, if the iron was impregnated second onto a calcined Rh–Mn–Li/SiO2 catalyst, it was more conducive to the dissociation and spillover of hydrogen, which could partly promote the reduction of Rh and Mn oxides. Based on the IR description and catalytic performance of the catalysts for CO hydrogenation, it is conceivable that the facile transformation of dicarbonyl Rh+(CO)2 into H–Rh–CO and Rh–CO–Fe is responsible for the higher selectivity of C2+ oxygenates over the catalyst, in which Fe was impregnated and calcined first followed by Rh–Mn–Li impregnation.