磷钨酸催化氧化木质素制备芳香醛的研究

A Study on the Catalytic Oxidation of Lignin and Preparation of Aromatic Aldehyde Compounds Carried by Phosphotungstic Acid

摘要: 木质素是唯一可大规模再生的芳香化合物资源，对木质素进行定向催化氧化解聚，可以制备得到芳香醛等化合物，用于重要的平台分子和精细化学品，有望为石油煤炭等不可再生资源的替代提供思路与方案。磷钨酸同时具备氧化性和酸性，其在有机溶剂中对木质素的催化氧化性能目前还未见有详细报道。本文通过正交实验设计等方法，讨论了磷钨酸对木质素模型分子的催化氧化性能，探讨了其催化机理。结果表明最优条件为甲醇：水(mL:mL) = 50:50，反应温度100℃，氧气压力1.5 MPa，反应时间3小时，转化率达到了91.3%。模型分子中的C-O键和C-C键均被催化断裂。在该条件下，将该催化剂应用于真实木质素的催化氧化反应中，得到的主要产物为酚类和芳香醛类，且产物分布较为集中。本文通过实验表明，磷钨酸对木质素的催化氧化解聚具有良好的活性和选择性，在木质素的转化与精制过程中具有良好的研究和利用价值。

Abstract: Lignin is the only large-scale renewable aromatic compound resource. Aromatic aldehyde com-pounds can be prepared to form the lignin via the directional catalytic oxidation and depolymeri-zation, which were utilized as the important platform molecules and fine chemicals. Through this way, a good solution was provided for the replacement of non-renewable resources, such as coal for oil. Phosphotungstic acid is a kind of heteropolyacid with both oxidation and acidity. The catalytic oxidation of lignin in organic solvents carried by phosphotungstic acid has not been reported in detail. In this paper, the catalytic oxidation properties of phosphotungstic acid on lignin model were discussed by orthogonal experiment design, and the catalytic mechanism was discussed. The results show that the optimal conditions are: methanol:water (mL:mL) = 50:50, reaction temper-ature 100˚C, oxygen pressure 1.5 MPa, the reaction time 3 hours, the conversion rate 91.3%. The C-O and C-C bonds in the model molecules are both cleaved. The optimal conditions are applied to the catalytic oxidation reaction of real lignin, and the main products are phenolic and aromatic aldehydes, and the product distribution is concentrated. The results of this paper show that phosphotungstic acid has good catalytic activity and selectivity in the process of lignin conversion and refined process, and also has good studying and using values.