工业木质素热化学解构途径与含氧官能团演变规律研究

The generation of value-added chemicals or qualitied biofuel from lignin via an effective and selective thermochemical conversion strategy is the key to improve the efficiency of biomass utilization..This study focused on the mechanistic routes of critical chemical bonds cleavage (like carbon-oxygen, carbon-carbon) during the lignin thermal-chemical depolymerization process and the evolution laws of oxygen-containing functional groups (hydroxyl, carbonyl, carboxyl and methoxyl) derived from the pyrolysis products. To investgate the decomposition routes of representative technical lignin (alkali lignin, biomass-to-ethanol residue lignin) under different pyrolytic conditions and the change rule of oxygen-containing functional groups and their effects on the products formation, the experiment was carried out by various novel methods. These typical analysis methods included pyrolysis combination with in situ - FTIR, pyrolysis –GC/MS mass spectrometry, spin trapping and EPR for intermediates indentification, substrate addition with model compounds contrast, theoretical simulation and calculation, and advanced qualitative and quantitative analysis method for pyrolysis products..The aim is to understand the breakage of the key chemical bonds and restructuring mechanism of industrial lignin, the formation mechanism of oligomers in the liquid product and ways to control its content. It will also know the relationship between the pyrolysis product composition and the internal structure, the pyrolysis operating conditions, the catalyst addition. It will provide basic and theoretical direction to the improvement the yield and stability of liquid products form the thermochemical depolymerization of technical lignin, the reduction of oligomer content, and the achievement of efficient conversion and value-added utilization of technical lignin.

高效、定向热化学转化木质素，制备高附加值化学品或高品位液体燃料是提高生物质资源利用效率的关键。本研究从木质素大分子热化学解聚过程关键碳-氧、碳-碳化学键的断裂途径、羟基、羰基、羧基、甲氧基等含氧官能团的变化规律入手，采用热解-原位FTIR联用、热解-气相色谱-质谱联用分析、反应中间产物的快速捕集与EPR分析、底物添加和模型物对照、计算机模拟与量化计算、产物的先进定性定量分析等研究方法和手段，揭示碱木质素（AL）、纤维素乙醇残余木质素（ERL）等代表性工业木质素在不同热解条件下的解聚途径、含氧官能团的演变规律及其对产物形成的影响。旨在认识工业木质素关键化学键的断裂与重组机制、液相产物中寡聚物的成因与控制途径、明晰影响热解产物组成结构的内在因素及工况条件、催化剂添加等外在因素，为提高工业木质素热化学解聚液相产物的收率和稳定性、降低寡聚物，实现其高效转化和高值化利用提供研究基础与理论指导。

木质素的高效、定向解聚，制备高附加值化学品或高品位液体燃料是提高生物质资源利用效率的关键。本研究从木质素大分子关键化学键断裂途径，含氧官能团变化规律入手，揭示了工业木质素在不同热解条件下的解聚途径、含氧官能团对产物形成的影响。.合成了不同侧链取代的苯乙基苯基醚（PPE）型β-O-4二聚体，研究了其热化学稳定性以及热解产物的生成规律，采用EPR原位追踪了热解自由基的变化规律。从侧链活性取代基对β-O-4′结构热解路径和中间产物的影响入手，从分子层面探讨侧链取代基对其热解的诱变效应。结果发现：PPE的侧链烯化成PSE后其热解反应活性大大降低。PPE侧链Cα和Cβ被含氧活性官能团所取代后，β-O-4结构的反应活性明显增强，α-羰基化有利于热解产物富集和定向解聚，而α-羟基化更有助于提高β-O-4结构的热解反应活性；在β-羟甲基化的条件下，α-羰基化更有利于Cβ-O键的断裂。羟基化对β-O-4结构的热解自由基反应具有促进作用，α-羰基更容易诱导自由基的生成，导致自由基反应在相对较低温度下就可以发生。通过选择性修饰木质素的酚羟基、侧链α-氧化官能团，可以调控木质素热解油的产率。热解过程中酚羟基脱氢形成苯醌结构是木质素热解过程中热解焦炭形成的主要原因。同时，甲氧基通过重排反应带走邻位酚羟基的氢原子，促进了醌型结构的形成，因此，通过预处理选择性地脱甲基可以减少热解固相产物的产率。苯环引入给电子基团，增加苯环电子云密度，抑制酚羟基脱氢形成醌型结构，可以抑制木质素热解中间产物缩合，减少热解固体产物的形成。.木质素在一定量氢气或氩气氛围下热解，产物中含氧官能团较少。工业木质素在碱溶液体系下与氧化石墨烯（GO）作用，GO在木质素大分子间形成插层，可以显著提高热解油中单酚的产率。这些研究成果为从木质素结构调控、添加催化剂等途径提升热化学解聚液相产物的收率和稳定性、降低寡聚物含量，提供了研究基础与理论指导。