Lignin valorization is strongly dependent on a right strategy for converting lignin into value-added products. Conversion of lignin into monomeric degradation products is one of the important avenues. In this study, chemical mechanisms and monomeric product compositions in hydrolysis (acidic and alkaline), hydrogenolysis, catalytic oxidation, electrochemical oxidation and reduction, photochemical and enzymatic degradation of native and technical lignins, and lignin model compounds are comparatively analyzed. The effect of the structure of a phenylpropane unit in lignin on the chemical reactivity of α-O-4 and β-O-4 bonds in cleavage reactions is also described. Published experimental data suggest some form of activation to be a necessary prerequisite for the splitting of a β-O-4 bond in all chemical reactions under consideration, the nature of which is dependent on the reagents and reaction conditions. Thus, in catalytic oxidation processes, a benzyl hydroxyl group is converted into carbonyl group at the first stage. Chemical transformation involving the α-position in a phenylpropane unit is a usual trigger of further lignin depolymerization. The yield of monomeric products of hydrogenolysis of native lignin is close to the theoretical one, reaching 23% in softwood and 51% in hardwood; in alkaline hydrolysis as well as oxygen and nitrobenzene oxidation of native lignin, the trend is the same that is explained in this study. On the other hand, the yield of monomeric products from isolated samples and technical lignins is much lower. A loss of arylether bonds in the process of lignin separation from wood and in wood pulping explains this difference.

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木材化学加工中芳醚键的木质素增值和断裂：小型综述

木质素的增值很大程度上取决于将木质素转化为增值产品的正确策略。将木质素转化为单体降解产物是重要的途径之一。在本研究中，对天然和工业木质素的水解（酸性和碱性）、氢解、催化氧化、电化学氧化和还原、光化学和酶降解以及木质素模型化合物的化学机制和单体产品组成进行了比较分析。还描述了木质素中苯丙烷单元的结构对裂解反应中 α-O-4 和 β-O-4 键的化学反应性的影响。已发表的实验数据表明，某种形式的活化是所有正在考虑的化学反应中 β-O-4 键分裂的必要先决条件，其性质取决于试剂和反应条件。因此，在催化氧化过程中，苄基羟基在第一阶段转化为羰基。涉及苯丙烷单元中 α 位的化学转化是进一步木质素解聚的常见触发因素。天然木质素氢解单体产物收率接近理论值，针叶木可达23%，硬木可达51%；在碱性水解以及天然木质素的氧和硝基苯氧化中，趋势与本研究中解释的相同。另一方面，来自分离样品和工业木质素的单体产品的产率要低得多。在从木材中分离木质素和制浆过程中芳醚键的丢失解释了这种差异。