Identification of a diagnostic structural motif reveals a new reaction intermediate and condensation pathway in kraft lignin formation†,Chemical Science

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Identification of a diagnostic structural motif reveals a new reaction intermediate and condensation pathway in kraft lignin formation†
Chemical Science ( IF 7.6 ) Pub Date : 2018-07-11 00:00:00 , DOI: 10.1039/c8sc02000k
Christopher S Lancefield ₁ , Hans L J Wienk ₂ , Rolf Boelens ₂ , Bert M Weckhuysen ₁ , Pieter C A Bruijnincx _{1,

3}

Affiliation

Kraft lignin, the main by-product of the pulping industry, is an abundant, yet highly underutilized renewable aromatic polymer. During kraft pulping, the lignin undergoes extensive structural modification, with many labile native bonds being replaced by new, more recalcitrant ones. Currently little is known about the nature of those bonds and linkages in kraft lignin, information that is essential for its efficient valorization to renewable fuels, materials or chemicals. Here, we provide detailed new insights into the structure of softwood kraft lignin, identifying and quantifying the major native as well as kraft pulping-derived units as a function of molecular weight. De novo synthetic kraft lignins, generated from (isotope labelled) dimeric and advanced polymeric models, provided key mechanistic understanding of kraft lignin formation, revealing different process dependent reaction pathways to be operating. The discovery of a novel kraft-derived lactone condensation product proved diagnostic for the identification of a previously unknown homovanillin based condensation pathway. The lactone marker is found in various different soft- and hardwood kraft lignins, suggesting the general pertinence of this new condensation mechanism for kraft pulping. These novel structural and mechanistic insights will aid the development of future biomass and lignin valorization technologies.

中文翻译：

诊断结构基序的鉴定揭示了硫酸盐木质素形成中的新反应中间体和缩合途径†

硫酸盐木质素是制浆工业的主要副产品，是一种丰富但未充分利用的可再生芳香族聚合物。在牛皮纸制浆过程中，木质素经历了广泛的结构改性，许多不稳定的天然键被新的、更顽固的键所取代。目前，人们对牛皮纸木质素中这些键和连接的性质知之甚少，而这些信息对于其对可再生燃料、材料或化学品的有效增值至关重要。在这里，我们提供了对软木牛皮纸木质素结构的详细新见解，识别和量化了主要的天然单元以及牛皮纸制浆衍生单元作为分子量的函数。由（同位素标记的）二聚体和高级聚合物模型生成的从头合成硫酸盐木质素，提供了对硫酸盐木质素形成的关键机制理解，揭示了不同的过程依赖的反应途径。新型硫酸盐衍生的内酯缩合产物的发现被证明对于鉴定先前未知的基于高香草醛的缩合途径具有诊断意义。内酯标记物存在于各种不同的软木和硬木硫酸盐木质素中，表明这种新的缩合机制对于硫酸盐制浆具有普遍相关性。这些新颖的结构和机制见解将有助于未来生物质和木质素增值技术的发展。

更新日期：2018-07-11

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