木质素基芳香醛类化合物的制备及其转化研究进展

Progress in the Preparation and Transformation of Lignin-based Aromatic Aldehydes

芳香醛化合物是合成染料、香料、农药、药品等精细化学品的重要原料。木质素是木质纤维素生物质中第二大组分,也是目前唯一可以生产芳香性化合物的可再生资源。催化氧化可在温和条件下转化木质素为具有高度官能化的芳香醛(对羟基苯甲醛、香草醛、紫丁香醛等),是实现木质素资源化利用的有效途径之一。首先介绍了木质素的结构特性和解聚机理,总结探讨了木质素结构对芳香醛制备的影响;进而从催化氧化解聚方式(湿式氧化与碱性硝基苯氧化,带均相和非均相催化剂的催化氧化解聚,光催化氧化以及电催化氧化)和催化剂类型(金属盐与金属卟啉、杂多酸等均相催化剂,金属氧化物及钙钛矿型氧化物等非均相催化剂)详细介绍当前木质素氧化解聚制备芳香醛的最新进展。此外,还对芳香醛升级转化制备2-甲氧基-4-甲基苯酚、芳腈、芳香酰胺及新型有机高分子材料等高附加值产品的具体研究情况进行总结。最后总结当前木质素氧化解聚研究存在的问题,并提出未来可能的发展方向。

Aromatic aldehydes were important raw materials for the synthesis of fine chemicals such as dyes,spices,pesticides and drugs.Lignin was the second largest component in lignocellulosic biomass,and was the only renewable resource for producing aromatic compounds.Catalytic oxidation could transform lignin into highly functionalized aromatic aldehydes(e.g.,p-hydroxybenzaldehyde,vanillin,syringaldehyde,etc.) under mild conditions,which was regarded as one of the effective ways to realize the resource utilization of lignin.Firstly,the structural characteristics and depolymerization mechanism of lignin were introduced,and the effects of lignin structure on the production of aromatic aldehydes were summarized and discussed.Then,recent progress in the preparation of aromatic aldehydes by oxidative depolymerization of lignin was introduced in detail from the methods of catalytic oxidative depolymerization methods(e.g.,wet oxidation and alkaline nitrobenzene oxidation,catalytic oxidative depolymerization with homogeneous and heterogeneous catalysts,photocatalytic oxidation and electrocatalytic oxidation) and types of catalysts(e.g.,metal salts and metal porphyrins,heteropoly acids and other homogeneous catalysts,metal oxides and perovskite oxides and other heterogeneous catalysts).Moreover,the upgrading and conversion of aromatic aldehydes into high value-added products such as 2-methoxy-4-methylphenol,aromatic nitrile,aromatic amides and new organic polymer materials were further summarized.Finally,the existing problems in the current research on lignin oxidative depolymerization were summarized,and the possible development direction in the future was proposed,which laid a foundation for lignin oxidative depolymerization and high value-added utilization.