Softwood forestry waste is an abundantly available lignocellulosic feedstock which could be converted into value-added chemicals via fast pyrolysis. However, its prominent recalcitrant nature resulting from the tightly intertwining of cellulose, hemicellulose and lignin as well as the catalytic effect of alkaline and alkaline earth metals (AAEMs) in it make the valorization of target pyrolytic chemicals particularly challenging. Glycerol pretreatment is a novel process to disrupt the recalcitrant structure of lignocellulose by separating it into three fractions. However, pretreatment effect from conventional heating assisted glycerolysis is poor due to low heat transfer. Introduction of external fields such as ultrasonic and microwave radiation could effectively improve the pretreatment effect. Microwave heating enabled better pretreatment effect than conventional oil bath heating due to its rapid heat transfer and athermal effect. Turbulence effects of ultrasonic radiation enhanced uniformly mixing of feedstock with glycerol, therefore further improving the pretreatment effect. The optimal glycerol pretreatment effect was realized by ultrasonic radiation integrated with microwave heating process, with pine sawdust deconstructed into 53.09 wt.% cellulose-rich fraction, 14.64 wt.% hemicellulose-derived sugars and 12.46 wt.% organosolv lignin, simultaneously removing 91.7 wt.% AAEMs. This considerably facilitated the formation of target pyrolytic chemical (levoglucosan), whilst preventing the production of undesired low molecular weight oxygenates such as acids, ketones, aldehydes. The highest yield of levoglucosan reached up to 52.07 wt.%. Kinetic analysis revealed that, higher activation energy is required for the glycosidic cleavage-based concerted reactions of cellulose into levoglucosan than AAEM catalyzed ring-breaking into light oxygenates. This work introduces an efficient method to produce value-added chemicals from forestry waste whilst reducing its hazardous impact on environment.

软木林业废料是一种丰富的木质纤维素原料，可通过快速热解转化为增值化学品。然而，由于纤维素，半纤维素和木质素的紧密缠结以及碱金属和碱土金属（AAEMs）的催化作用，其显着的顽强性使其对目标热解化学品的价位化提出了特别的挑战。甘油预处理是通过将木质纤维素分为三个部分来破坏木质纤维素的顽固结构的新方法。然而，由于传热低，常规加热辅助甘油分解的预处理效果很差。引入诸如超声波和微波辐射的外部场可以有效地改善预处理效果。微波加热由于其快速的热传递和无热作用，比常规的油浴加热具有更好的预处理效果。超声辐射的湍流效应增强了原料与甘油的均匀混合，因此进一步提高了预处理效果。最佳的甘油预处理效果是通过超声波辐射与微波加热工艺相结合实现的，将松木屑分解为53.09 wt。％的富含纤维素的馏分，14.64 wt。％的半纤维素衍生糖和12.46 wt。％的有机溶剂木质素，同时去除了91.7 wt 。％AAEM。这大大促进了目标热解化学品（左旋葡聚糖）的形成，同时防止了产生不希望的低分子量含氧化合物，例如酸，酮，醛。左旋葡聚糖的最高产量达到52.07wt。％。％。动力学分析表明，与AAEM催化的开环成轻质的含氧化合物相比，基于糖苷裂解的纤维素向左旋葡聚糖的协同反应需要更高的活化能。这项工作引入了一种有效的方法，可以从林业废弃物中生产增值化学品，同时减少其对环境的有害影响。