木质素原位氢解与精制过程中双功能水滑石类催化剂作用机制研究

High-valued application of industrial lignin is the bottleneck for the utilization of forest resources. In-situ hydrogenolysis coupled with refining for the conversion of industrial lignin to liquid fuel with high effective hydrogen carbon ratio (H/Ceff), is an effective pathway to achieve the full utilization of forest residues. Previous studies revealed that multicomponent metallic oxide materials based on hydrotalcite precursors could achieve the simultaneous hydrogenation, dehydration and isomerization during the catalytic hydrogenolysis and refining of lignin, which could lead to the obvious improvement of H/Ceff in the reaction products. Based on previous researches, a series of bifunctional non-precious metal catalysts based on hydrotalcite precursors will be prepared and introduced to the catalytic in-situ hydrogenolysis of industrial lignin assisted by microwave heating in complex solvents (mixture of phenols and hydrogen-donor solvent). Then the fundamental mechanisms and evolution regulations for the catalytic hydrogenolysis of lignin will be investigated considering the effect of complex solvents, catalysts and microwave heating. The catalytic hydrodeoxygenation mechanisms will be revealed by studying the refining of depolymerized lignin. The relations between the structural characteristics of catalysts (metal components, acid-base property, etc) and catalytic properties, as well as the change of H/Ceff before and after the catalytic hydrodeoxygenation will be investigated. The molecular transformation regulations will be illustrated by analyzing the product distributions, which will help to discover the transformation pathways of oxygen-containing functional groups (-OH, -OCH3, etc) in depolymerized lignin. Finally, the in-situ hydrogenolysis regulatory mechanism and refining mechanism will be illustrated over bifunctional hydrotalcite-based catalysts. This project will solve the basic scientific problem concerning the hydrogen transfer promoted by bifunctional hydrotalcite-based catalysts during the hydrogenolysis and refining of lignin, which will provide solid theoretical support for the full utilization of forest resources.

工业木质素的高值化利用是林木资源利用的瓶颈，通过原位氢解与精制制备高有效氢碳比液体燃料，是实现林木剩余物全质化利用的有效途径。木质素氢解与精制前期研究发现，水滑石作为前驱体制备的复合金属催化材料，能够同步实现酚类化合物加氢、脱水及异构化的基本反应规律，产物有效氢碳比显著提升。本项目在此基础上，制备系列双功能水滑石类非贵金属催化剂，研究催化剂酸碱性、金属协同作用与复合溶剂（酚类-供氢溶剂）在微波辅助下协同催化木质素氢解规律；研究木质素降解产物复杂酚类组分催化加氢脱氧过程机理，探索催化剂结构特性（金属组分、酸碱性等）在降解产物结构重整过程中的作用规律，揭示酚羟基、甲氧基等含氧官能团在加氢脱氧过程中的分子结构转变途径；阐明双功能水滑石类催化剂作用下的工业木质素原位氢解调控机制和产物精制过程机理。解决木质素原位氢解与加氢精制过程中催化剂促进氢转移的基础科学问题，为林木资源的全质化利用提供理论支撑。

木质素作为一种具有芳香结构的可再生资源，其催化转化制备液体燃料及精细化学品是生物质资源替代化石能源的重要途径。木质素资源化利用主要通过催化解聚与加氢精制来实现，木质素解聚主要包括热解、氧化降解和氢解等方法，均存在单酚收率低、后续转化利用困难等问题，而加氢精制存在依赖贵金属等问题。因此，针对上述难题，本项目提出创制基于铜基、镍基的高活性非贵金属类催化剂，并将微波作用引入木质素催化解聚与加氢精制。以工业木质素为原料，探索了超临界乙醇体系、微波-低碳醇溶剂体系木质素催化解聚，发展了定频微波-低碳醇溶剂协同铜基、镍基催化剂促进木质素氢解的新方法，发现在定频微波辅助木质素氢解过程中，微波响应催化剂协同原位氢可促进木质素解聚；能够在相对温和条件下（常压、120-160 ℃、40-80 min）实现木质素催化解聚制备解离多酚/单酚。在解离木质素催化转化方面，申请人初步发展了木质素解离多酚（酚类二聚体等）二次催化解聚新路径，发现NiLa双金属催化剂可同步实现酚类二聚体中不同C-O键（α-O-4、β-O-4、4-O-5等）断键及解聚所得单酚类同步催化转化，为木质素资源化利用受限于解离产物单酚收率低的难题提供了新思路。申请人在本项目中取得了好于预期的研究成绩，相关成果共发表学术论文 10 篇（其中，1区论文4篇，2区论文2篇，IF>5以上论文5篇）；申请发明专利 2 项。