Rational highly dispersed ruthenium for reductive catalytic fractionation of lignocellulose.

Abstract

Producing monomeric phenols from lignin biopolymer depolymerization in a detachable and efficient manner comes under the spotlight on the fullest utilization of sustainable lignocellulosic biomass. Here, we report a low-loaded and highly dispersed Ru anchored on a chitosan-derived N-doped carbon catalyst (RuN/ZnO/C), which exhibits outstanding performance in the reductive catalytic fractionation of lignocellulose. Nearly theoretical maximum yields of phenolic monomers from lignin are achieved, corresponding to TON as 431 mol_phenols mol_Ru^-1, 20 times higher than that from commercial Ru/C catalyst; high selectivity toward propyl end-chained guaiacol and syringol allow them to be readily purified. The RCF leave high retention of (hemi)cellulose amenable to enzymatic hydrolysis due to the successful breakdown of biomass recalcitrance. The RuN/ZnO/C catalyst shows good stability in recycling experiments as well as after a harsh hydrothermal treatment, benefiting from the coordination of Ru species with N atoms. Characterizations of the RuN/ZnO/C imply a transformation from Ru single atoms to nanoclusters under current reaction conditions. Time-course experiment, as well as reactivity screening of a series of lignin model compounds, offer insight into the mechanism of current RCF over RuN/ZnO/C. This work opens a new opportunity for achieving the valuable aromatic products from lignin and promoting the industrial economic feasibility of lignocellulosic biomass.