Staged biorefinery of Moso bamboo by integrating polysaccharide hydrolysis and lignin reductive catalytic fractionation (RCF) for the sequential production of sugars and aromatics

Towards a waste-free biorefinery was of the lignocellulose valuable and sustainable conversion. In this study a staged biorefinery for lignocellulose conversion to maximum valuable products was proposed and experimentally demonstrated by using Moso bamboo (Phyllostachys heterocycla cv. Pubescens). It is an integrated sequential process including hemicellulose acidolysis with FeCl3 as the catalyst, reductive catalytic fractionation (RCF) of lignin with Pd/C and sulfuric acid as catalysts, and enzymatic hydrolysis of cellulose. The influence of acid FeCl3 catalyzed hemicellulose acidolysis on the subsequent RCF of lignin and enzymatic hydrolysis of cellulose were investigated and the optimized conditions for hemicellulose acidolysis were obtained. The yield of pentose, aromatic monomers, and glucose was respectively 85.8 wt%, 28.5 wt%, and 64.3 wt% relative to the initial hemicellulose, lignin, and cellulose contained in the Moso bamboo. The conversion and the products were analyzed and characterized using gas chromatography mass spectrometry (GC MS), Fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), and heteronculear single quantum coherence nuclear magnetic resonance (HSQC-NMR) spectrometry. The results indicated that hemicellulose acidolysis with FeCl3 resulted in the dissolution of some low molecular weight lignin and the cleavage of lignin-carbohydrate linkages of 2-O-Ac-β- d -xylopyranoside, while the connections of 3-O-Ac-β- d -xylopyranoside, phenyl glycoside and the β-ether linkages in lignin were remained. However, excessive removal of hemicellulose negatively influenced the stability of the lignin structure and delignification. RCF of lignin resulted to the hydrolysis of lignocellulose, yielded cellulose and aromatic monomers via the cleavage of β-ether bonds.