中文摘要：

木质素是自然界中含量巨大的天然酚类聚合物,其总量仅次于纤维素。由于其结构复杂性,仅有不到2%的木质素用于工业生产,因此实现木质素的高效综合利用是目前该领域的难题,而木质素的氧化还原转化为芳香化合物是目前一个重要且有前景的手段：木质素氧化解聚能显著降低其主要化学键键能,促进木质素转化为香草醛、紫丁香醛和高香草醛等高度官能化的单体;而木质素还原解聚可将其结构中含氧官能团脱除,转化为低氧/无氧木质素生物油,可作为高热值生物燃油,且在反应中能显著抑制缩合反应的进行。本文简要介绍了木质素的结构单元以及联接方式,同时从反应条件和催化剂等方面全面综述了国内外木质素氧化还原解聚的最新研究进展,并对其反应机理进行了详细探讨。在此基础上,针对当前木质素解聚过程中的难题提出了未来该领域的研究重点和方向。

英文摘要：

Lignin is a natural phenolic polymer and the second most abundant component next to cellulose in almost all plant biomass.However,only 2%of lignin is applied to industrial production due to the complexity of lignin structure.Therefore,the importance of comprehensive utilization of lignin should be addressed.It is a very important and promising approach for oxidative and reductive depolymerization of lignin polymer into aromatic compounds in lignin valorization.Oxidative depolymerization of lignin can significantly reduce the bond energy of main chemical bonds in lignin,which promotes the conversion of lignin into highly functionalized lignin monomer,such as vanillin,syringaldehyde,homovanillin.The reductive depolymerization can remove the oxygen-containing functional groups of the lignin and facilitate the transformation of lignin into low-oxygen and oxygen-free bio-oil,which can be applied to high caloric value bio-fuel.Besides,condensation reaction is conspicuously suppressed during reductive depolymerization.A brief introduction of the lignin structure unit,connecting and the recent progress in oxidative and reductive depolymerization of lignin are reviewed intensively.In addition,the catalytic mechanism for the depolymerization of lignin is also discussed.Furthermore,forthcoming research emphasis and directions of lignin depolymerization are proposed at the end of the review based on existing problems in this area.