林木基磁性固体酸一步催化木质纤维制备糠醛的构效关系及转化机制研究

The conversion of lignocellulose into furfural is considered as one of the important approaches for the high-value utilization of biomass. Based on the problems of low productivity, severe pollution, difficult recovery of catalysts and low utilization of raw materials during the furfural industrial production, this project is mainly to carry out the research on the one-step catalytic conversion of lignocellulose into furfural via woody-based magnetic solid acids. In view of the advantages of structural diversity and high carbon content of woody biomass, woody-based magnetic solid acids with the characteristics of highly efficient, environmental friendly and easy recycle will be synthesized from the forest biomass (Anthocephalus chinensis, Ficus microcarpa, Eucalyptus, Poplar, et al.), which combine the features of magnetism and solid acids. The efficient reaction system for the one-step conversion of lignocellulose into furfural will be established. The influences of the characterization of raw materials, pretreatment ways and the reaction conditions on the physicochemical properties and the catalytic performance of woody-based magnetic solid acids will be investigated, and the structure-function relationship of the prepared catalysts will be discovered. The effect of Lewis acid and Brønsted acid on the furfural production will be revealed. The depolymerization and conversion mechanisms of hemicelluloses will be clarified, and the kinetic model for the one-pot conversion of lignocellulose into furural also will be established. This study will provide theoretical and technique guidances for the improvement of furfural production process and the efficient utilization of lignocellulose.

由木质纤维素制备糠醛是生物质高值化利用的重要途径之一。基于目前糠醛工业生产存在的产率低、污染大、催化剂回收困难、原料利用率低等问题，本项目主要开展林木基磁性固体酸一步催化木质纤维素生成糠醛的研究。针对林木生物质结构多样和含碳率高的特点，以林木生物质（黄梁木、榕树、桉木、杨木等）为原料，将磁性机制和固体酸特性相结合，设计合成高效环保并易于重复利用的林木基磁性固体酸催化剂；建立木质纤维素一步法制备糠醛的高效反应体系；探讨林木生物质原料特性、预处理方式以及合成条件对林木基磁性固体酸催化剂理化性质以及催化性能的影响，构建林木基磁性固体酸催化剂的构效关系；揭示Lewis酸和Brønsted酸对糠醛生成的作用机制；阐明反应过程中半纤维素的解聚和转化机理；建立木质纤维素一步法制备糠醛的动力学模型。该研究为糠醛生产工艺的改良以及木质纤维素高效利用提供理论基础和技术指导。

糠醛是一种重要的平台化合物，广泛应用于医药、材料、石油化工等领域。本项目以桉树、毛竹、水稻秸秆为原料，合成了多种具有较高催化活性和重复利用性的磁性固体酸催化剂，并将其应用于一步异相催化木质纤维生成糠醛、低聚木糖、还原糖等平台化合物中，探讨了原料特性、预处理条件和合成条件对催化剂理化性质和催化性能的影响。研究结果显示，所合成的三种磁性固体酸催化剂在催化木质纤维转化中具有较高的催化活性和重复利用性能；稀酸稀碱预处理能有效提高催化剂的酸性和催化活性；自水解预处理能促进催化剂制备碳化过程中β-O-4键的断裂，碳化产物中G型木质素含量上升，品质提高，桉树基磁性固体酸催化剂的比表面积随着自水解预处理温度和时间的增加而增加；温水浸渍能有效提高生物质的转化效率。此外，本项目还构建了木质纤维素高效转化制备糠醛的新型反应体系，并揭示了影响水解过程的关键因素及速控步骤。研究结果显示，采用MIBK/H2O-NaCl-HCl混合体系对桉树进行处理可有效提高糠醛渣酶解制备还原糖的得率，当MIBK/H2O比例为5:5，HCl浓度为0.3M，在150oC下处理60min 糠醛得率最高；以固体酸为催化剂，采用两步法先后催化甘蔗渣生成糠醛和乙酰丙酸，得率分别达88.1%和62.1%；采用微量稀碱湿法混球磨及后续在温和条件下水热预处理以提高甘蔗渣和狼尾草的酶解糖化效率, NaOH浓度和原料化学成分对还原糖产率起着重要的影响。相关研究为推动糠醛工业的改良及促进木质纤维生物质的高效利用提供理论基础和技术指导。