基于热解-氨化耦合的木质素制备芳香胺反应机理和调控机制研究

Due to its complex composition and stability, lignin is difficult to be used effectively and largely abandoned. Aromatic amines are important petroleum-based chemicals with wide application. In this study, based on coupling pyrolysis and catalytic ammonization reactions, catalytic fast pyrolysis under ammonia atmosphere is proposed to make full use of the aromatic ring and oxygen-containing functional groups in lignin in order to realize efficient production of aromatic amines in one-step. In view of the problems of unclear reaction mechanism and catalyst structure-activity relationship in the conversion process, the effect of active nitrogen source on lignin pyrolysis under ammonia-rich atmosphere and its migration mechanism are investigated firstly. Then, through investigating the on-line pyrolysis of lignin model compounds with the help of quantum calculations, the selective enrichment mechanism of lignin and its cracked phenolic compounds to simple aromatic amines will be elucidated. Subsequently, the activity and selectivity of catalyst for catalytic ammonization reaction are studied by controlling the properties of catalyst, such as acidity-alkalinity, doping element type, pore structure, particle size, etc; the theoretical structure-activity relationship of catalyst in the pyrolysis- ammonization reaction is revealed through various characterization means. Finally, through full-factorial design of experimental method, the process parameters are optimized systematically to generate aromatic amines efficiently from lignin. This work is expected to provide theoretical guidance and practical basis for sustainable production of aromatic amines and high-value utilization of lignin.

木质素由于组成复杂、结构稳定，难以被有效利用而被大量废弃。芳香胺是一类具有广泛应用的重要化学品。本项目将热解和催化氨化反应耦合，充分利用木质素结构中的芳香环结构和含氧官能团（酚羟基等），实现木质素一步定向高效制备简单芳香胺。针对转化过程中存在的反应机制和催化剂构效关系不明确等问题，本项目首先通过富氨氛围木质素热解特性研究阐明活性氨源对木质素热解影响及氮迁移机制；随后通过模型化合物在线热解-氨化实验与量化计算结合，揭示木质素向简单芳香胺转化的反应路径和转化机制；进一步通过对催化剂的晶粒尺寸、孔道结构、酸碱性和骨架元素等性质进行调控，结合热解-氨化反应效果与催化剂表征结果，探究催化剂性质对木质素制备芳香胺的影响规律和构效关系；最终通过全因子设计法研究热解-氨化过程中的各种工况因素耦合对木质素热解氨化制备芳香胺的影响，从而为芳香胺的绿色可持续生产和木质素高值化利用提供理论指导和实践基础。

芳香胺（如苯胺，甲基苯胺，二甲基苯胺）是一类重要的工业化学品，可作为原料合成橡胶硫化促进剂、显影剂、染料、农药试剂、药品、炸药和二苯基甲烷聚氨酯(MDI)等材料和精细化学品。每年我国芳香胺市场交易额高达数百亿，其中苯胺每年生产和需求量最大。木质素，是数量上仅次于纤维素的第二天然高分子材料，在生物质中含量约为20-40%，也是自然界中唯一能够提供大宗可再生芳香基化学物的可再生资源。为了充分利用生物质中的含氧官能团，本报告通过氨气氛围催化快速热解的方法实现木质素一步定向制备具有高附加值芳香胺；通过对木质素热解中间体和产物分布规律进行分析，以及对催化剂的酸碱性、骨架元素（金属掺杂改性）、孔道结构和晶体颗粒大小等因素以及对反应温度、载气组成等因素系统调控实现氨气氛围选择性利用木质素结构中的芳香基官能团和含氧官能团并催化快速热解高效制备芳香胺，最终提出一条能够实现木质素高值化利用和芳香胺绿色、可持续生产的新路径。因此，以木质素为原料实现木质素的资源化和高附加值化利用具有重要的意义。