Depolymerization of Lignin Catalyzed by Complex Metal Oxide in Supercritical Methanol北大核心CSCD

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. © 2018, Editorial Board of «Chemistry and Industry of Forest Products». All right reserved.