预处理是木质纤维材料高效转化为燃料乙醇的关键步骤之一。 通过预处理可以实现木质素及半纤维素等屏障性组分的大量移除, 增加纤维素酶对纤维素的生产性吸附, 从而有效提高后续的酶水解得率。 泡桐（Paulownia）年产量大、 生长周期短、 加工废料多, 是制备生物能源和其他化学品极具潜力的原料。 为实现泡桐木质生物质原料到生物乙醇的高效转化, 促进泡桐原料的高效酶水解, 故而对原料进行预处理以打破其原有的生物抗性, 降解并脱除酶水解屏障性组分, 暴露并保留更多纤维素组分。 本研究以泡桐作为实验材料, 使用乙酸协同亚硫酸钠对原料进行化学预处理, 分析不同处理方法对原料化学组分及结构特性的影响。 组分分析显示： 预处理后, 样品葡聚糖相对含量均有不同程度增加, 其中碱性亚硫酸钠协同处理泡桐增加最为明显。 数据显示, 碱性亚硫酸钠协同处理具有很好的脱木素作用, 同时可以降解溶出部分木聚糖组分, 因此其葡聚糖相对含量显著增加至67.48%（未处理泡桐的葡聚糖相对含量为46.81%）。 此外, 分别采用FTIR, XRD及XPS等表征方法对所有泡桐样品的理化结构进行分析, 以探究不同预处理对样品结构产生的影响。 FTIR分析表明： 碱性亚硫酸钠协同处理后木质素特征吸收明显减弱, 纤维素特征吸收增强, 表明木质素有一定脱除, 纤维素相对含量有所增加。 XRD分析显示： 预处理后泡桐纤维表面受到破坏, 木质素及半纤维素等无定型物质被部分脱除, 纤维素结晶度均有不同程度增加。 其中, 碱性亚硫酸钠协同处理后纤维素结晶度显著增加至58.98%（未处理材的纤维素结晶度约为40.23%）, 002峰位向右侧偏移, 衍射峰衍射强度明显增强, 峰形变高且尖锐程度增大； XPS分析表明： 碱性亚硫酸钠协同处理后, 样品表面碳水化合物含量增加, 表面木质素含量减少。 所有表征分析均显示碱性亚硫酸钠协同处理对泡桐结构破坏性最大, 木质素降解脱除程度最高, 纤维素保留程度最好, 这有助于增加纤维素酶对纤维素的可及性, 有效提高后续的纤维素酶水解效率, 进而促进泡桐原料到燃料乙醇的高效转化。 结构表征分析结果与化学组分规律保持一致。

Pretreatment is one of the key steps in the efficient conversion of lignocellulose into fuel ethanol. During the pretreatment process, a large amount of barrier components such as lignin and hemicellulose can be removed, which can effectively increase the productive adsorption of the cellulase to cellulose, thereby effectively improving the subsequent enzymatic hydrolysis yield. Paulownia has a large annual output, short growth cycle and high processing waste. It is a potential material for the preparation of bio-energy and other chemicals. In order to achieve high-efficiency conversion of paulownia woody biomass material to bioethanol, and promote efficient enzymatic hydrolysis of paulownia material, the raw material was pretreated to break its original biological resistance, degrade and remove enzymatic hydrolysis barrier components, expose and retain more cellulose components. In this work, Paulownia was used as the experimental material, and the raw material was chemically pretreated with acetic acid and sodium sulfite, analyzing the effect of different treatment methods on the chemical compositions and structural characteristics of samples. The composition analysis showed that the relative content of glucan in the samples increased to different degrees after pretreatment, and the alkaline sodium sulfite synergistic treatment of paulownia increased most obviously. The data showed that the alkaline sodium sulfite synergistic treatment had a good delignification effect and could degrade some xylan component, so the relative content of glucan was significantly increased to 67.48% (the relative content of glucan in the raw material was 46.81%). In addition, the physicochemical structures of all paulownia samples were analyzed by FTIR, XRD and XPS to explore the effects of different pretreatments on the structure of samples. FTIR analysis showed that the characteristic absorption of lignin was significantly weakened by the alkaline sodium sulfite synergistic treatment, and the characteristic absorption of cellulose was enhanced, indicating that the lignin had a certain removal, and the relative content of cellulose had increased; XRD analysis showed that the fiber surface of pretreated Paulownia was destroyed, the amorphous substances such as lignin and hemicellulose were partially removed, and the crystallinity of cellulose increased to varying degrees. Among them, after alkaline sodium sulfite synergistic treatment, the cellulose crystallinity increased significantly to 58.98% (the cellulose crystallinity of the raw material was about 40.23%), the peak position of 002 shifted to the right, the diffraction intensity of diffraction peak increased obviously, the peak shape became higher and the sharpness increased; XPS analysis showed that the surface carbohydrate content increased and the surface lignin content decreased after the alkaline sodium sulfite synergistic treatment. All the structural characterization analysis showed that the alkaline sodium sulfite synergistic treatment had the greatest destructive effect on the structure of Paulownia, the most lignin degradation and the best cellulose retention, which could increase the accessibility of cellulase to cellulose and effectively improve the subsequent cellulase hydrolysis efficiency, and thereby promote the efficient conversion of paulownia raw material to fuel ethanol. The results of structural characterization analysis were consistent with the chemical composition rules.