Formation of C2 oxygenates and ethanol from syngas on an Fe-decorated Cu-based catalyst: insight into the role of Fe as a promoter

Abstract

In this study, the formation mechanism of C₂ oxygenates and ethanol from syngas on Fe-decorated Cu bimetallic catalyst was investigated using density functional theory (DFT) calculations together with microkinetic modeling. The results showed that CH₂ was the most favored monomer among all the CH_x (x = 1–3) species over the FeCu bimetallic catalyst, which was more favorable than CH₃OH formation. Namely, the FeCu catalyst exhibited a good selectivity toward CH₂ formation instead of CH₃OH formation in syngas conversion. Starting from the CH₂ monomer, CH₂CO and CH₃CO via CO insertion into CH₂ and CH₂CO hydrogenation were the major products instead of C₂ hydrocarbons or methane, CH₃CO was successively hydrogenated to ethanol via CH₃CHO and CH₃CH₂O intermediates. Moreover, the microkinetic modeling showed that the FeCu bimetallic catalyst had a high selectivity toward ethanol rather than methanol and methane. Further, the addition of Fe into the Cu catalyst promoted CH_x formation by accelerating C–O bond cleavage, suppressed methanol formation, and facilitated C₂ oxygenate formation rather than methane formation, suggesting that the synergetic effect between Fe and Cu played an important role in the formation of C₂ oxygenates and ethanol. In addition, it is believed that the insights derived from this study can provide clues for the catalyst design of oxygenate synthesis and other bimetallic catalytic systems.