Effect of pH on Hemicellulose Extraction and Physicochemical Characteristics of Solids during Hydrothermal Pretreatment of Eucalyptus

Zeguang Yang, Liming Cao, Yan Li, Min Zhang, Fanyan Zeng, Shuangquan Yao

Abstract


The effects of pH on residual solids (RS), total dissolved solids (TDS), carbohydrates, and lignin in eucalyptus during hydrothermal pretreatment were studied. The balance between RS and TDS was obtained at pH 4.0 in hydrothermal pretreatment with pre-adjustment pH. The yield of hemicellulose increased, and oligosaccharides dominated. Hemicellulose had the highest dissolution rate, and cellulose and lignin had the lowest dissolution rate at pH 4.0. The crystallinity index (CrI) and structural transformation of lignin was analyzed by X-ray diffraction (XRD) and nuclear magnetic resonance spectroscopy (NMR) with or without pretreatment. The CrI at pH 4.0 was 64.2% higher than that with the traditional hydrothermal pretreatment (62.1%). The β-O-4 bonds, OMe, and phenylcoumarane of lignin were protected. The highest hemicellulose extraction and minimal physicochemical structural changes were obtained at pH 4.0.

Keywords


Eucalyptus; Hydrothermal pretreatment; Pre-adjustment pH; hemicellulose; Lignin

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