The research progress on characteristics of lignin's chemical depolymerization products and its depolymerization mechanism

The research progress in recent years on the characteristics of lignin's chemical depolymerization products and the depolymerization mechanism were reviewed in this paper. Brief introduction was made of the lignin macromolecule formation process, structure unit, connecting way and the yield, composition, and of the characteristics in three-phase product(liquid phase, gas phase and solid phase) by hydrothermal depolymerization and hydrogenation depolymerization and catalytic oxygen depolymerization processes. The characteristics of liquidphase product by the process of different sources of lignin and different depolymerization methods were mainly discussed; the mechanism of chemical depolymerization was also reviewed. Finally, the existing problems in the current lignin's chemical depolymerization process were summarized, the forthcoming research direction for lignin depolymerization was put forward and the development of lignin utilization was prospected.