Valorizing Lignocellulose into Aromatic Compounds Via Oxidative Catalytic Fractionation and Transformation Strategy Catalyzed by Polyoxometalates

Abstract

Utilizing renewable resources as substitutes for fossil resources is a crucial pathway towards achieving sustainability, with biomass conversion being a significant avenue. Catalytic fractionation of lignocellulose represents an effective approach to biomass conversion, wherein lignin is selectively separated from lignocellulose and depolymerized into high-value aromatic monomers within the reaction system. However, existing technologies face challenges such as low product selectivity and difficult separation. Herein, we employ oxidative catalytic fractionation (OCF) using polyoxometalates (POMs) as catalysts and a methanol/water mixture as solvent to directly oxidize and catalyze lignin in pine wood lignocellulose into aromatic compounds under an O2 atmosphere, while preserving cellulose for subsequent utilization. The process yields up to 22.5% aromatic monomers, with vanillin and methyl vanillate as the main products (calculated based on Klason lignin). Our approach provides a novel perspective for achieving highly selective oxidative fractionation and depolymerization of lignin, thus contributing to the valorization of lignocellulose.

Keywords: Lignocellulose, Lignin, Oxidative catalytic fractionation, Polyoxometalates, Aromatic monomers