Self-hydrogen Supplied Catalytic Fractionation of Raw Biomass into Lignin-derived Phenolic Monomers and Cellulose-rich Pulps

Lignocellulosic biomass is one of the most well-studied and promising green carbon sources. Fullest utilization of lignocellulosic biomass in hydrogen-free and mild conditions to produce phenolic monomers while preserving cellulose-rich pulps is challenging and has far-reaching significance. Here, we report an innovative strategy to convert lignocellulosic biomass into lignin oils and cellulose-rich pulps without exogenous hydrogen under mild conditions over Pt/NiAl2O4 catalyst. In this process, the structural hydrogens in hemicellulose are acted as hydrogen source to realize the fractionation and depolymerization of lignin into phenolic monomers while keeping cellulose intact, which is named self-hydrogen supplied catalytic fractionation (SCF). By using water as solvent, theoretical yield of phenolic monomers (46.6 wt%, with propyl(ethyl) end-chained syringol and guaiacol as main products) is achieved at 140 oC for 24 h, with 90 % cellulose intact in birch sawdust. This H2-free process can be extended to other biomass (hardwood, softwood and grass) and can be scaled up. The Pt/NiAl2O4 catalyst also shows good stability in recycling as well as a regeneration treatment. This work provides a new strategy to achieve high utilization of lignocellulosic biomass for sustainable biorefinery by using water as solvent without exogenous hydrogen under mild conditions.