The lignin hydrothermal processing is an important option but a full understanding of the role played by the water molecules in the depolymerization of lignin is still lacking. In order to clarify the role of the water molecules in the depolymerization of lignin, the evolution of chemical bonds, microstructural changes, and possible mechanisms of product generation were compared during the pyrolysis process under vacuum and water conditions using Reactive Molecular Dynamics Simulation. Compared with vacuum conditions, the role of water changes with temperature, identifying three stages: promotion (1200–1800 K)-inhibition (2100–2400 K)-promotion (2700–3000 K). Also compared with vacuum conditions, hydrothermal processing can promote the cleavage of the ether bonds while inhibiting the destruction of carbocycles. Water molecules promote the depolymerization of lignin into more C₄-molecules, thereby generating more combustible gas resources. Based on the research results, the pyrolysis conditions of lignin can be flexibly controlled to obtain solids, liquids or gases.

木质素水热处理是一个重要的选择，但仍缺乏对水分子在木质素解聚中所起作用的充分了解。为了阐明水分子在木质素解聚中的作用，使用反应分子动力学模拟比较了真空和水条件下热解过程中化学键的演变、微观结构变化和产物生成的可能机制。与真空条件相比，水的作用随温度而变化，分为三个阶段：促进（1200-1800 K）-抑制（2100-2400 K）-促进（2700-3000 K）。同样与真空条件相比，水热处理可以促进醚键的断裂，同时抑制碳环的破坏。_4-分子，从而产生更多的可燃气体资源。基于研究结果，可以灵活控制木质素的热解条件以获得固体、液体或气体。