氧化锌催化木质素选择性解聚制备对香豆酸甲酯

Selective depolymerization of lignin to methyl p-coumarate catalyzed by metal oxides

  • 摘要: 木质素是自然界中含量最丰富的芳香族可再生碳资源,具有极高的利用价值。针对当前木质素解聚技术存在反应条件苛刻、产物选择性低等难题,构建了一种廉价的金属氧化物催化剂体系,研究了草本木质素选择性解聚制备对香豆酸甲酯的性能。考察了不同金属氧化物、反应温度、反应时间以及溶剂等因素对于对香豆酸酯收率和选择性的影响。研究结果表明,金属氧化物ZnO对于草本木质素选择性解聚制备对香豆酸甲酯的过程具有最佳的催化活性。在优化的反应条件下,可获得9.8%的对香豆酸甲酯收率和61.6%的选择性;通过对木质素解聚产物的分析并结合反应前后木质素的傅里叶红外光谱(FT-IR)和二维核磁(2D HSQC NMR)表征结果发现,木质素分子中H结构单元的选择性断裂是其催化解聚过程中对香豆酸甲酯收率和选择性高的主要原因。

     

    Abstract: As the most abundant and renewable aromatic source on the earth, lignin is a good alternative to fossil fuel on producing versatile petrochemicals and biofuel. However, current techniques for lignin conversion generally suffer from some key problems of harsh reaction condition and low selectivity of products. In this study, an efficient process was provided for selective depolymerization of herbaceous lignin to a fine chemical of methyl p-coumarate (MPC) by using cost-effective catalysts of metal oxides. The influences of different metal oxides, reaction temperature, time and solvent on the yield and selectivity of MPC were systematically investigated. The results showed that ZnO exhibited the best catalytic activity, where the yield and selectivity of MPC reached 9.80% and 61.6%, respectively, at the optimized reaction conditions. Furthermore, the results of products distribution and comparative investigation on the raw and unreacted lignin using FT-IR and 2D HSQC NMR spectra demonstrated that the efficient cleavage of the ester linkage in lignin was responsible for this good MPC yield and selectivity. Therefore, this work provides a new insight on producing fine chemicals from the renewable lignin.

     

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