碳化钨催化木质素芳醚键选择氢解研究

Lignin is a complex three-dimensional amorphous polymer with relatively intractable property. To make use of this biomass resource, this project put forward a new route for the production of aromatic compounds via selectively hydrocracking of lignin over tungsten carbide catalyst, which exhibits noble metal-like behavior in catalysis. Based on our previous progress in conversion of cellulose to ethylene glycol, this project will first take aryl ether dimeric lignin model compounds as the substrates to study the activation mechanism of aryl ether bonds over tungsten carbide; in the meantime, we will explore the effect of the monomer structure on the cleavage of the aryl ether bonds. By characterizing the changes in the evolution of the tungsten carbide phase as well as the particle size distribution coursed by adding small amount of a second metal, the synergistic effect between transition metal and tungsten carbide will be explored. Under optimized reaction conditions with the best catalyst, this project will further focus on the direct hydrogenolysis of lignin with the aim to produce renewable aromatic compounds. Through in-situ physical and chemical characterization in a versatile autoclave with crystal window, this project will explore the reaction multiphase behaviour, the changes of thermodynamic parameter and the structure of the catalyst, as well as the formation of the intermediates and the products, in the aim to control the products selectivity and understand the complex mechanism of lignin hydrogenolysis process. This project will set up some theoretic rules in the development of non-noble metal catalysts for biomass conversion and will drive our technology nearer to cost-efficient production of chemicals from lignocellulose.

针对木质素复杂的结构及顽固的化学性质，提出用具有类贵金属性质的碳化钨催化木质素选择氢解制备芳香化合物的新思路。在前期碳化钨催化纤维素制乙二醇研究基础上，本项目从具有?-O-4及其它芳香醚键的木质素模型化合物出发，研究不同芳醚键在碳化钨催化剂上的活化机理，考察木质素单体结构对氢解活性的影响规律。深入研究第二金属组分对碳化钨的晶相、分散度及表面性质的影响，阐明过渡金属组分与碳化钨催化剂的协同作用机制，制备出廉价的高活性和高选择性催化剂。在优化条件下，重点研究木质素直接选择性氢解反应。借助具有原位表征功能的可视高压反应装置，探测反应过程中相行为、热力学参数、催化剂结构变化及中间物种的生成和转化，实现对木质素氢解行为的调控。结合模型反应结果，阐明木质素催化氢解机理，最终实现木质素定向解聚制芳香化合物。本项目的实施将对木质纤维素资源全组分高效利用起到推动作用，同时为发展非贵金属催化技术提供参考。

针对木质素复杂的结构及顽固的化学性质，本项目发展了用具有类贵金属性质的碳化钨催化木质素选择氢解制备芳香化合物的新思路。以木质素选择性氢解制酚类化合物为研究目标，通过模型反应并结合多种现代物理化学表征手段，从分子水平角度研究了木质素芳醚键在碳化钨催化剂上的活化机制和反应路径，阐明了不同钨物相在木质素氢解中的作用；深入研究了不同来源的木质素结构、化学组成对碳化钨催化氢解活性的影响规律；探索了钨基双金属催化剂的制备方法及在木质素氢解反应中的活性，阐明了过渡金属组分与钨的协同作用机制。通过对活化机制及木质素转化机理的深入认识，制备出高活性、廉价的非硫化态碳化钨催化剂和钨基双金属催化剂，实现木质素高选择性催化氢解制备芳香化合物。此外，本项目以碳化钨为氢解催化剂，借助“氧化-氢解”两步法解聚策略，实现真实木质素选择转化为含羰基的芳香化学品，提出了新的科学认识：解聚效率相对于一步氢解法有明显下降，但氧化-氢解的两步策略可显著改变产物选择性。深入探索了获得以上反应结果的根本原因。本项目还发展了均（多）相铼催化剂用于木质素催化高效解聚。以上进展为新型高选择性非贵金属催化剂研制和木质素高效转化利用提供了理论基础和重要参考。