Selective C2+ Alcohol Synthesis from Syngas Boosted by MnOx-Doped CoFe Bimetallic Alloy Carbide Catalysts

Abstract

Direct synthesis of higher alcohols (HA) from syngas is an attractive route for converting nonpetroleum carbon feedstocks into high value-added fuels and chemical products. CoFe alloy carbide catalysts are promising for this reaction, but facilitating the alloy carbide formation is still challenging. Herein, a series of Mn-promoted catalysts with regulated proximity between Mn and CoFe₂O₄ were prepared. It was found that the manganese species with close intimacy greatly facilitated the formation of ε’-(Co_xFe_1–x)_2.2C, reaching a maximum content of 88.4 wt % over the Mn_0.25Co₁Fe₂ catalyst. A space-time yield toward HA of 137.9 mmol·g_(Co+Fe)^–1·h^–1 with stability over 300 h was achieved over this catalyst, ranking top among the literature. In addition, MnO_x also greatly promoted the CO dissociation. The closely interacted MnO_x and ε’-(Co_xFe_1–x)_2.2C sites benefited the coupling of CH_x* and CO*/CHO*, leading to the modification of the Anderson-Schulz–Flory law and the enhanced C₂₊ alcohols fraction in total alcohols up to 94.1 wt %. Moreover, the Mn content was also optimized. This promotional effect of manganese may provide possibilities for the use of CoFe alloy carbide catalysts in higher alcohol synthesis.