Abstract: [Objective] Chemical pretreatment is a critical step for transforming a biomass to its value-added lignocellulosic biomass polymeric products, and the elucidation of pretreatment mechanism is important for improving the thermal treatment efficiency.[Method] Four-year-old bamboo was pretreated with acid, alkali and glycerine at 117℃ and 135℃,respectively. The structural features of the pretreated and the native samples were characterized and compared using a set of spectroscopy and wet chemistry methods including FTIR, XRD,respectively.[Result] The results showed that the holocellulose and cellulose yields increased significantly, and the lignin removal rate was better for dilute alkali (NaOH) pretreatment than that for dilute acid (H₂SO₄) and glycerin pretreatments. Furthermore, for the same solutions, the compositional changes of samples were more remarkable at 135℃ than those at 117℃, and the same degradation of hemicelluloses was observed for different processing.All of the pretreatment samples exhibited relatively low average degree of polymerization (DP) values, indicating that the pretreatment processing could change the super molecular structure.The X-ray diffraction results showed that after different chemical heat treatments, the 002 peak position was clearly offset, the crystalline width and half peak width decreased, but the crystalline intensity increased significantly, and the relative crystallinity declined at 117℃ and gradually increased at 135℃. The results obtained by Fourier infrared spectrum were consistent with those of the X-ray diffraction.[Conclusion] For both 117℃ and 135℃ pretreatment temperature in sand bath, alkali pretreatment effects were stronger than that of the dilute acid and glycerin. These results would provide foundation and basis for the research of energy transformation of lignocellulose raw material.

Key words: bamboo, pretreatment, Flourier infrared spectrum, average degree of polymerization, X-ray diffraction, thermogravimetric analysis