Laboratory of Biomass Conversion, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Kyoto, 611-0011, Japan.
Laboratory of Applied Radio Engineering for Humanosphere, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan.
ChemSusChem. 2020 Sep 7;13(17):4510-4518. doi: 10.1002/cssc.202000502. Epub 2020 May 15.
Model erythro, phenolic, and nonphenolic lignin β-O-4 dimer compounds are treated with copper oxide and H O at the electronic field maximum position of a single-mode 2.45 GHz microwave system equipped with a cavity resonator. The products obtained through microwave heating and oil-bath heating with the same reaction vessel and temperature profile are quantitatively compared. Dimer degradation is found to proceed through consecutive elementary reactions. The phenolic dimer is dehydroxylated and this is followed by the spontaneous cleavage of C -C and C-O-C bonds to produce guaiacol, vanillin, and vanillic acid. The reaction of the nonphenolic dimer produces veratric acid, veratraldehyde, and guaiacol. Microwave irradiation accelerates cleavage of the side chain and the oxidation of vanillin to vanillic acid. However, no acceleration of veratraldehyde oxidation to veratric acid or aromatic ring cleavage to produce dicarboxylic acids is observed. The selective acceleration of elementary reactions during the degradation of model lignin compounds indicates that microwaves interact with reaction intermediates that are sensitive to electromagnetic waves.
模型愈创木酚型、酚型和非酚型木质素β-O-4 二聚体化合物在配备有腔式谐振器的单模 2.45GHz 微波系统的电子场最大值位置，用氧化铜和 H O 处理。定量比较了通过微波加热和油浴加热在相同的反应容器和温度曲线下获得的产物。通过连续的基本反应发现二聚体降解。酚型二聚体脱羟，然后 C-C 和 C-O-C 键自发裂解生成愈创木酚、香草醛和香草酸。非酚型二聚体的反应生成藜芦酸、藜芦醛和愈创木酚。微波辐射加速侧链的裂解和香草醛氧化成香草酸。然而，没有观察到藜芦醛氧化成藜芦酸或芳环裂解生成二羧酸的加速。模型木质素化合物降解过程中基本反应的选择性加速表明，微波与对电磁波敏感的反应中间体相互作用。
