Synergistic effects of ionic liquid plus alkaline pretreatments on eucalyptus: Lignin structure and cellulose hydrolysis

• Published in: Process biochemistry (1991) 2015-06, Vol.50 (6), p.955-965
• Main Authors: Xu, Ji-Kun, Sun, Yong-Chang, Sun, Run-Cang
• Format: Article
• Language: English
• Subjects: Cellulose; Cellulose hydrolysis; Ethanol; Ethyl alcohol; Eucalyptus; Hydrolysis; Ionic liquid; Ionic liquids; Lignin; Molecular structure; Pretreatment
• ISSN: 1359-5113; 1873-3298
• DOI: 10.1016/j.procbio.2015.03.014

•Ionic liquid and alkaline pretreatments were combined for woody biomass biorefinery.•The influence of this integrated biorefinery on lignin structure and subsequent cellulose hydrolysis was investigated.•A maximum yield of 35.0% was achieved for lignin prepared from the 1-allyl-3-methylimidazolium chloride pretreated feedstock.•Pretreatment improved the yield and purity of lignin and its physicochemical properties were modified slightly.•The synergistic pretreatment of eucalyptus led to significant improvement of cellulose hydrolysis. The structure of eucalyptus lignin after ionic liquid (IL) and alkaline ethanol pretreatment processes as well as the influences of this integrated biorefinery on subsequent cellulose hydrolysis were investigated. A maximum yield of 35.0% was achieved for lignin (L1) prepared from the 1-allyl-3-methylimidazolium chloride pretreated feedstock. The lignins prepared with ILs pretreatment contained lower amount of carbohydrates (0.78–2.13%) than milled wood lignin (MWL, 9.11%) and alkaline ethanol lignin (AEL, 2.29%), and exhibited inhomogeneous molecular weights distribution (Mw, 1395–3050g/mol) in contrast to MWL (Mw, 2765g/mol). The lignin preserved basic structure after pretreatment, but had relatively higher amount of β-O-4′ linkages, syringyl units to guaiacyl units (S/G) ratios, and other ending structures. The S/G ratios of lignin increase in the following order: MWL