Depolymerisation of lignin to well-identified aromatic chemicals has been recognized as one of the most promising ways to valorise lignin. Widely investigated hydrogenolysis and oxidative depolymerisation strategies selectively disrupt labile interunit C - O linkages (e.g., β − O − 4 linkages) but are ineffective on the disruption of robust interunit C - C linkages (e.g., methylene linkages) in condensed technical lignins. Herein, an efficient phenol-assisted depolymerisation (PAD) process was developed to selectively celave methylene linkages in condensed lignins. In the process, phenol not only served as a solvent to facilitate lignin dissolution but also scavenged methylene linkages from condensed lignin polymers to facilitate the depolymerisation. Results showed that scavenging C-induced methylene moieties resulted in monomers without a side chain whereas scavenging formaldehyde-induced methylene moieties led to monomers with side chains. Lignin monomers (or monophenols) yields up to 40 % and bisphenols yields up to 42 % could be achieved via the new PAD process, which were better than those resulting from existing depolymerisation methods. Besides, the residual polyphenols could be used to synthesize lignin-formaldehyde adhesives for plywood applications. We anticipate that this practical lignin valorisation method would create additional revenue for the pulp industry and enable economic biorefineries.

中文翻译：

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苯酚辅助将缩合木质素解聚为单酚/多酚和双酚


木质素解聚为明确的芳香族化学物质已被认为是木质素增值最有前途的方法之一。广泛研究的氢解和氧化解聚策略选择性破坏了缩合工业木质素中不稳定的单元间C - O 连接（例如，β - O - 4 连接），但对破坏稳定的单元间C - C 连接（例如，亚甲基连接）无效。在此，开发了一种有效的苯酚辅助解聚（PAD）工艺来选择性地裂解缩合木质素中的亚甲基键。在此过程中，苯酚不仅充当促进木质素溶解的溶剂，而且还从缩合木质素聚合物中清除亚甲基键以促进解聚。结果表明，清除C诱导的亚甲基部分产生没有侧链的单体，而清除甲醛诱导的亚甲基部分则产生具有侧链的单体。通过新的 PAD 工艺，木质素单体（或单酚）收率高达 40%，双酚收率高达 42%，优于现有解聚方法。此外，残留的多酚可用于合成用于胶合板应用的木质素-甲醛粘合剂。我们预计这种实用的木质素增值方法将为纸浆行业创造额外收入并实现经济的生物精炼。