廉价金属催化体系中木质素定向氢解及其调控机制研究

As lignin is the only renewable nonfossil resource in nature which can offer aromatic chemicals, catalytic depolymerization of lignin into phenols are of highly strategic and scientific significance from the viewpoint of the utilization of lignin resource for producing energy fuels and chemical feedstocks under current background of global severe oil competition. It is difficult to achieve catalytic depolymerization of lignin in a selective fashion, because this complicated chemical transformation always gives various products and the regulation mechanism for selective depolymerization is still unclear. In this project, selective hydrogenolysis of lignins into phenols is expected by using noval catalytic systems designed on the basis of clarification of selective bond activation mechanism of lignin. This would provide theoretical roots and key technical support for valorization of lignin. The reactivity, selectivity and regulation mechanism for core skeletons and linkages in lignin will be explored through the reactivity and mechanistic study of model compounds. The selective hydrogenolysis of lignins derived from various plants using nonprecious metal catalysts are to be investigated, leading to formation of low-molecular-mass aromatic chemicals having different functional groups. The utilization of lignin-based low-molecular-mass compounds is expected to expand in energy, chemical industry and pharmaceuticals, by development derivatization and valorization of these molecules. It is proposed to establish a new protocol for sequential utilization of biomass components through catalytic depolymerization of lignin selectively.

木质素是自然界唯一能提供可再生芳香基化合物的非化石资源，通过催化降解转化为苯酚类有机分子作为能源和化工原料，对于在当今国际能源竞争激烈的情况下具有重要的战略和科学意义。木质素催化降解的化学过程复杂、产物众多，对降解路径的选择性调控机制缺乏认识，难以实现木质素的定向催化降解。本项目提出依托木质素选择性键活化机理导向的金属催化反应体系，实现木质素定向催化氢解及选择性调控，为实现木质素高值化利用提供基础理论及关键技术支撑。通过木质素模型化合物反应及机理研究，揭示木质素核心骨架及连接键反应活性、选择性及控制机制；创建以廉价金属为催化剂的木质素氢化降解体系，实现多物种来源木质素的选择性氢解，制备具有不同官能团、性能的木质素单分子产物；开发木质素基单分子的衍生化及高值化反应体系，拓展其在能源、化工、医药等领域的应用；创建以木质素选择性催化降解为核心步骤的生物质原料全组分分级利用新方案。

木质素是自然界最丰富的可再生芳香碳氢资源，木质素通过降解转化为适用于下游生产的单分子芳基化合物是其高值化的基点，是双碳背景下构建非石化芳香化学品的重要路径与方案。然而，木质素自身结构的复杂性及反应活性的多样性，导致木质素定向降解为酚类单体十分困难，当前采用的贵金属催化剂也限制了未来的产业化应用。本项目针对木质素催化降解为酚类单体过程中面临的化学过程复杂、产物多重化难以分离，降解路径的选择性调控机制不明确、催化剂高效高选择性与低成本的匹配等问题，开展了系统性研究。项目设计了新型同位素氘标记的木质素模型化合物，通过对其反应性研究及产物分子氘元素追踪，排除了已报道所有机理在常规及本课题发展的催化体系中的适用性，提出并阐明了木质素协同断键新机制；创建以钼、镍等廉价金属为活性中心的木质素氢解催化体系，实现源于阔叶材、针叶材及草本植物的多种木质素的选择性氢解，定向制备了含不同官能团且易分离纯化的酚类单体，并将其应用于功能高分子材料制备；通过植物筛查工作，确定价格低廉、产量丰富的大戟科植物种子（麻风、石栗、油桐、蓖麻）果壳中富含C-型木质素，率先完成C-型木质素与传统木质素地拆解与分离，设计制备原子级分散的金属催化剂，实现了C-木质素高效选择性降解为丙烯基邻苯二酚的转化过程。本项目已公开发表SCI收录论文14篇，中文核心论文2篇，包括12篇中科院一区top论文，论文被引用361次（基于google scholar统计）。申请国家发明专利6件，授权3件。培养了6名博士研究生，6名硕士研究生。在本项目资助下，两名项目组成员获得职称晋升，项目负责人于2019年入选中组部“万人计划”科技创新领军人才。与预期目标相比较，本项目超额完成了任务。