In Situ Encapsulated CuCo@M-SiO2 for Higher Alcohol Synthesis from Biomass-Derived Syngas

Higher alcohol synthesis (HAS) from biomass-derived syngas (CO/H-2) is of considerable interest but has a challenge to achieve a satisfying yield, as it is a competitive reaction between C-C coupling and CO insertion. Herein, we employed a solvent (dihydric alcohol) coordination-assisted impregnation strategy to synthesize a series of catalysts with Cu and Co encapsulated in ordered mesoporous SiO2 (denoted as CuCo@M-SiO2). This synthesis strategy could effectively anchor Cu and Co cations at a close distance owing to the solvent coordination effect. Additionally, the carbon derived from the thermal decomposition (inert atmosphere) of the solvent ligand portrayed a critical role in in situ reduction of Cu and Co species and synchronous confinement. It also helped structural dispersant ("spacer") and inhibited the aggregation of Cu nanoparticles (NPs). The as-prepared CuCo@M-SiO2 catalyst contained multiple types of synergistic active sites (Cu-0, Co-0, and Con+) that collaborated with each other to enhance the higher alcohol yield. It is confirmed that the CO conversion and higher alcohol selectivity were closely related to solvent-assisted ligands. Among the selected solvent ligands (ethylene glycol, 1,2-propanediol, and 1,4-butanediol), the CuCo@M-SiO2 catalyst derived from 1,2-propanediol-assisted impregnation exhibited a remarkably catalytic performance because of the appropriate confinement effect with smaller CuCo NPs. Notably, the CO conversion was as high as 82.2% with space-time yield toward 16.1 mmol gcat(-1) h(-1) of ethanol. A narrow alcohol distribution of C-1-C-3-mixed alcohols was over 97.2%. These synthetic strategies may provide new avenues for designing effective and stable catalysts for HAS.