木质纤维原料富含羟基, 可通过液化处理转化为具有较高反应活性的液态产物, 实现其高值化利用。 纤维原料的液化过程中存在降解和缩聚反应的竞争反应, 直接影响液化产物的特性。 为了研究枫香果实的液化反应过程, 以聚乙二醇和丙三醇(4∶1 V/V)为液化试剂, 对枫香果实进行不同时间(30, 60, 90, 120和150 min)的液化处理。 利用傅里叶红外光谱(FTIR)结合主成分分析(PCA)、 X射线衍射(XRD)分别对液化残渣和液化产物进行表征。 结果表明枫香果实的液化率随反应时间延长逐渐提升, 最高为88.79%。 基于液化率和羟值确定枫香果实的最佳液化时间为120 min, 此时液化率为87.91%, 液化产物的羟值为280 mg KOH·g-1。 FTIR和XRD分析表明液化反应初期以木质素和半纤维素的降解反应为主； 液化后期, 结晶纤维素开始降解, 同时伴随着缩聚反应的发生。 主成分分析发现, 不同液化时间得到的液化残渣的官能团分布相对独立, 可以作为判断枫香果实在液化过程中各组分降解的依据。 液化时间90 min为液化过程的转折点, 此时主导反应逐渐由降解转为缩聚反应。 此外, 为了探究枫香果实液化产物在聚氨酯泡沫应用上的可行性, 添加不同含量(10%, 20%和50%)的枫香果实液化产物成功制备得到了聚氨酯泡沫。 FTIR分析表明, 枫香果实的液化产物可代替多元醇制备聚氨酯泡沫, 且液化产物的添加并未改变聚氨酯泡沫的化学结构。 研究结果为进一步探究木质纤维资源的液化过程和枫香果实的液化利用提供了理论依据。

The conversion of lignocellulosic biomass with high content of hydroxyl groups to liquid substances with high reactivity through liquefaction was considered a promising route for realizing their high-value utilization. The competitive reaction of degradation and polycondensation in lignocellulosic biomass’s liquefaction process directly affects the liquefaction product’s characteristics. The liquefaction of Chinese Sweet Gum’s (Liquidambar formosana) fruit was carried out at various times (30, 60, 90, 120, and 150 min) using polyethylene glycol and glycerin (4∶1 V/V) as liquefaction reagents to investigate the degradation and polycondensation reaction process in liquefaction. Fourier infrared spectroscopy (FTIR) combined with principal component analysis (PCA) and X-ray diffraction (XRD) were used to characterize the liquefied residues and liquefied products. The results showed that the liquefaction efficiency gradually increased with the extension of the reaction time, and the highest liquefaction efficiency was 88.79%. The optimal liquefaction time was 120 min when the liquefaction efficiency was 87.91%, and the hydroxyl value of the liquefied product was 280 mg KOH·g-1. FTIR and XRD analysis showed that lignin and hemicellulose were priority degraded at the initial stage of the liquefaction reaction. The crystalline cellulose began degrading at a later stage, accompanied by a polycondensation reaction. Principal component analysis results suggested that the distribution of functional groups of the liquefied residues obtained at different liquefaction times was relatively independent, which could be used as the basis for judging the degradation time of each component in the liquefaction process. Moreover, the polycondensation reaction gradually became dominant after 90 min of liquefaction. In addition, to explore the feasibility of liquefaction products as biomass polyols in the polyurethane foam field, polyurethane foams were successfully prepared by adding different contents of liquefaction products (10%, 20%, and 50%). FTIR showed that liquefaction products could replace polyols in the preparation of polyurethane foam, and the addition of liquefaction products did not change the chemical structure of polyurethane foam. The study would provide a theoretical basis for further exploring the liquefaction reaction of lignocellulosic resources and the liquefaction utilization of L. formosana fruit.