Liquefaction of bamboo biomass and production of three fractions containing aromatic compounds

Abstract

Depolymerization of lignin to produce value-added aromatic monomers has attracted increasing attention since these monomers can be used as phenol replacement in production of phenolic resins. Here a one-pot depolymerization of bamboo lignin was investigated to obtain aromatic platforms with low molecular weight using acidic catalyst and ethanol. Three fractions (1#, 2#, and 3#) containing different molecular weight distributions of aromatic compounds could be efficiently extracted using water-organic solvent system via a stepwise fractionation process by gradual removal of solvent. The fractions distribution was found to be primarily dependent on the reaction temperature and time. When the temperature was increased from 160 °C to 200 °C, the yield of fractions containing aromatic products increased significantly from 19.1 wt% to 27 wt%, the same change trend was found by changing the time, and the yield of aromatic products increased from 22.4% to 26.7% with an increase of time from 10 min to 30 min. The bioproducts were characterized by using gas chromatography/mass spectrometry (GC–MS), gel permeation chromatography (GPC) and two-dimensional heteronuclear single-quantum coherence (2D HSQC NMR). As evidenced by GC–MS spectra, the three fractions were mainly comprised of phenolic derivatives, and the relative contents of phenolic compounds took up about 80% of the total area of each fraction. With the similar physiochemical properties of the fractions, aromatic platforms could provide a new paradigm of bamboo lignin utilization for renewable energy and value-added biochemicals.