High-value utilization of lignin is critical to improve the economic viability of integrated biorefineries. In this study, HBr was employed as a trifunctional catalyst to perform depolymerization, phenolation and demethylation of lignin in phenol to improve the reactivity of lignin and the obtained product was further directly used to prepare phenolic foams without purification. With the aid of microwave irradiation, a reduced reaction time and mild reaction conditions were achieved. The results showed that the phenolic hydroxyl content increased from 2.89 mmol/g to 5.90 mmol/g (increased by 104%) while the methoxyl group content dropped from the 4.75 mmol/g to 3.37 mmol/g (decreased by 30%) under the optimized conditions (10% HBr, 90 °C and 2 h). The structure changes of lignin were investigated by FT-IR, GPC, ¹H, ³¹P, and 2D HSQC NMR analyses. Due to the enhanced activity of lignin, the activation energy and characteristic curing temperature of the modified lignin-based phenolic resin (103.27 kJ/mol, 130.1 °C) was markedly lower than that of the unmodified lignin-based phenolic resin (113.48 kJ/mol, 139.4 °C) according to differential scanning calorimetry (DSC) analysis. Further characterization of the modified lignin-based phenolic foam showed it has better thermal insulation and mechanical properties than that of unmodified lignin-based phenolic foam, which provides a value-added application of lignin as insulating foam material.

木质素的高价值利用对于提高综合生物精炼厂的经济可行性至关重要。在这项研究中，HBr被用作三官能催化剂，以进行木质素在苯酚中的解聚，酚化和去甲基化，以改善木质素的反应性，所得产物无需纯化即可直接用于制备酚醛泡沫。借助微波辐射，可以缩短反应时间并降低反应条件。结果表明，在此条件下，酚羟基含量从2.89 mmol / g增加到5.90 mmol / g（增加104％），而甲氧基含量从4.75 mmol / g减少到3.37 mmol / g（减少30％）。优化的条件（10％HBr，90°C和2 h）。木质素的结构变化通过FT-IR，GPC，^{1进行了研究}H，³¹ P和2D HSQC NMR分析。由于木质素的活性增强，改性木质素基酚醛树脂的活化能和特征固化温度（103.27 kJ / mol，130.1°C）明显低于未改性木质素基酚醛树脂的活化能和特征固化温度（113.48 kJ / mol）。摩尔，139.4℃），根据差示扫描量热法（DSC）分析。改性木质素基酚醛泡沫的进一步表征表明，它具有比未改性木质素基酚醛泡沫更好的绝热性和机械性能，从而提供了木质素作为绝缘泡沫材料的增值应用。