Insights into the Active Phase and Reaction Mechanism on K-Promoted Mo₆S₈ Catalysts for Higher Alcohols Synthesis from Syngas

The production of higher alcohols from syngas represents a sustainable green energy conversion technology that contributes to reducing the dependence on fossil fuels. Among the various catalytic systems, potassium-modified molybdenum-sulfide-based catalysts have emerged as one of the most effective options. However, the precise composition and structure of the catalytically active phase in this system remain unclear, and the proposed mechanism needs to be verified by more experimental data. In this study, K-promoted Mo6S8 catalysts were prepared and their catalytic performance, active phase, and reaction mechanism were explored. Through experimental characterizations combined with the reported theoretical calculations, KMo6S8 was identified as the active phase of this catalyst system. The K-promoted Mo6S8 sample with K/Mo = 0.5 exhibited high C2+OH distribution and selectivity, 84.7 and 35.9%, respectively, comparable to the highest reported values of 88.7 and 41.8% under similar reaction conditions. In situ DRIFT spectroscopy combined with DFT calculations revealed that the enhanced catalytic performance originated from the efficient generation and synergistic interaction of the reaction intermediates CHx* and CHxO* on the KMo6S8 active phase.