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Chemistry and Industry of Forest Products ›› 2018, Vol. 38 ›› Issue (4): 52-60.doi: 10.3969/j.issn.0253-2417.2018.04.009

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Depolymerization of Lignin Catalyzed by Complex Metal Oxide in Supercritical Methanol

YE Jiewang1,2, JIANG Jianchun1, JIN Zhenfu2, ZHANG Weigang2, ZHANG Xiaochun2   

  1. 1. Institute of Chemical Industry of Forest Products, Chinese Academy of Forestry(CAF), Nanjing 210042, China;
    2. Cooperative Innovation Center of Bamboo Resources and Efficient Utilization in Zhejiang Province, Zhejiang Agriculture & Forestry University, Lin'an 311300, China
  • Received:2018-02-06 Online:2018-08-25 Published:2018-08-10

Abstract: Cu-Ni doped layered double oxide (LDO) catalysts were prepared from hydrotalcite-like precursors. The effects of reaction conditions on the catalytic lignin depolymerization productswere investigated in supercritical methanol. The results showed that in the condition of n(Cu):n(Ni)=1:1, at 280℃ for 8 h,Cu0.5Ni0.5Mg3Al-LDO used as catalyst with 30% dosage, the monomer yield from lignin depolymerization was up to 67.5%, while the yields of tetrahydrofuran(THF) insoluble residue and charwere least. The liquid phase product were qualitatively and quantitatively analyzed by GC-MS, and it was observed that the yield of the cyclic compound was 64.43%, and the acyclic product was only 10.65%, indicating Cu/Ni-LDO catalyst can effectively break the bonds between the lignin structural units, while with a lowactivity to break the aromatic ring structure.Charforming reactions in lignin depolymerization were effectively suppressed by Cu/Ni co-doped LDO catalyst, and the monomer yield was significantly improved. Hydrogenolysis and hydrogenation reaction in lignin depolymerization were promoted obviously at higher temperature,leading to a higher monomer yield. The supercritical temperature of methanol showed a significant effect on the depolymerization of lignin:When the reaction temperature was higher than 240℃, the yield of monomer increased significantly and the yields of insoluble residue and char decreasedon the other hand. The degradation rate of lignin remained above 90% after the catalyst was recycled for three times. XRD, ICP and N2 adsorption and desorption experiments showed that leaching of Mg was the main cause for catalyst deactivation. Cu/Ni-LDO catalyst can effectively promote the depolymerization of lignin into small molecule monomer compounds in supercritical methanol medium.

Key words: lignin, depolymerization, layered double oxides (LDO), supercritical methanol, hydrogenation

CLC Number: