Synergistic Catalysis: A Powerful New Strategy for the Production of Lignin-Derived Aromatic Monomers

Efficient and selective conversion of lignin into aromatic monomers (AMs) is extremely essential for the economic feasibility of biorefinery. Nevertheless, the high catalytic efficiency of solid acid catalysts (SACs) for lignin conversion into AMs is remarkably weakened by the present of water produced during the above reaction leading to the deactivation and leaching of acidic sites. More importantly, the directional preparation of SACs with well-defined mesopores, hydrophobicity, and Bronsted-Lewis acidic sites still remains a grand challenge for hetero-geneous catalyst development. To overcome these limitations, a desired multifunctional poly(ionic liquid)s (MFPILs) with above-mentioned structural and chemical properties were successfully constructed by an innovative synergistic regulation-induced co-polymerization. Then, MFPILs exhibit more excellent catalytic performance than poly(ionic liquid)s containing Lewis acidic site, Bronsted acidic site, or hydrophilicity alone with 47.9% conversion of lignin and 24.6 wt% yield of AMs, which is the excellent yield reported for the catalytic hydroconversion of lignin using non-precious-metal catalysts. The high catalytic performance of MFPILs for the production of lignin-derived AMs are attributed to the synergistic co-catalysis of the hydrophobic micro -environment, Bronsted-Lewis acidic sites, and mesoporous confinement, which was further confirmed by water contact angle, H2 temperature programmed desorption, and adsorption experiment. Further, MFPILs featuring magnetic recovery properties can be recycled for at least 10 run times without a significant lower catalytic activity. The work not only sheds some light on fabricating the novel SACs, but also develops a powerful new strategy to produce lignin-derived AMs.