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Effects of aluminum chloride-catalyzed hydrothermal pretreatment on the structural characteristics of lignin and enzymatic hydrolysis

Shen, Xiao-Jun, Wang, Bing, Huang, Pan-Li, Wen, Jia-Long, Sun, Run-Cang
Bioresource technology 2016 v.206 pp. 57-64
Eucalyptus camaldulensis, Fourier transform infrared spectroscopy, X-ray diffraction, aluminum, aluminum chloride, biomass, cellulose, crystal structure, enzymatic hydrolysis, glucose, hemicellulose, high performance liquid chromatography, lignin, lignocellulose, nuclear magnetic resonance spectroscopy, scanning electron microscopy, temperature
In this study, Eucalyptus camaldulensis was pretreated with 0.02M aluminum chloride (AlCl3) at 140–180°C to obtain digestible substrates for glucose and lignin. The effects of AlCl3-catalyzed hydrothermal pretreatment on the degradation of carbohydrates, structural changes of lignin, crystallinity, morphologic changes, and cellulose conversion of the pretreated biomass have been investigated by HAPEC, HPLC, FT-IR, XRD, CP/MAS NMR, SEM, and 2D-HSQC NMR. Results showed that the pretreatment significantly removed hemicelluloses and cleaved β-O-4 linkages of lignin at high temperatures. Under an optimum condition (at 170°C for 1h), almost all of hemicelluloses were removed and most of β-O-4 linkages in lignin were cleaved, and 77.8% cellulose conversion of the pretreated biomass was achieved, which was 7.3-fold higher than that of the original biomass. In short, this process was regarded as a promising approach to achieve an efficient conversion of lignocellulosic biomass to fermentable glucose and residual lignin.