Research Progress in Application of Lignin and Its Derivatives Supported Metal Catalysts in Organic Synthesis

Abstract

The attention of biomass-based catalysts has been continuously increased due to the proposal of carbon neutralization development concept. The use of lignin as a support for transition metal catalysts for the preparation of heterogeneous catalysts in the field of organic synthesis can greatly improve the utilization value of lignin. The extensive presence of oxygen-containing functionalities in the lignin structure provides a variety of binding sites for the loading of metal catalysts, and metal particles can be efficiently captured by physical adsorption/deposition, ion exchange, and electrostatic complexation with hydroxyl functional groups. The structure of lignin is firstly introduced, and the methods for preparing heterogeneous catalysts are then described. Lignin and its derivatives supported metal catalysts catalyzed Click reaction, Glaser reaction, Huisgen [3＋ 2] cycloaddition reaction, Heck reaction, Suzuki reaction, Sonogashira reaction, Stille coupling, Michael addition/dehydration tandem, Electrophilic ring-opening reaction, Fridel-Crafts type reaction, ethylene polymerization and other reactions. Thus, at the end of this review, the existing problems and development trends are prospected. Keywords functionalized lignin; lignin-supported metal catalyst; heterogeneous catalysis; organic synthesis; green chemistry 木质素一词最早由 Schulze [1] 于 1857 年提出, 来源 于拉丁语"lignum", 意思是木头. 它是植物界中仅次 于纤维素的一类重要的有机高聚物. Adler [2] 于 1977 年 提出了第一个全木质素结构, 木质素被认为是一类具 有多种官能团的高度聚合物, 其中包括甲氧基、羧基、 烷基、羰基、醇羟基和酚羟基. 由于木质素结构的多 样性和复杂性, 运用高效、精确的各种表征方法确定 木质素的结构, 进而掌握它的物理和化学性质对于实 现木质素的有效利用极为重要. 超滤、蒸气压渗透法、 质谱法、静态/动态光散射和凝胶渗透色谱法(GPC)通 常用于测定分子量(包括 M w 和 M n ), 元素分析用于测 量各种元素的含量(碳、氢、氧、硫和磷等), 傅里叶变 换 红 外