Comprehensive depolymerization of lignin from lignocellulosic biomass: A review

Converting biomass to produce renewable chemicals is one of the significant ways to realize the development of green chemistry and sustainable chemical industry. As the main component of lignocellulosic biomass, lignin is the most abundant natural polyphenol. Its unique phenolic properties and high carbon content make it potentially exploited. Biomass lignin depolymerization can be divided into thermochemical, chemical catalysis, electrocatalysis, and biological depolymerization methods. In this review, the catalytic reaction systems involved in different methods of lignin depolymerization were extensively described from various aspects, and the degradation products and reaction mechanisms were discussed and analyzed. The effects of novel green-deep eutectic solvents on biomass lignin depolymerization were reviewed in particular. Each method of biomass lignin depolymerization has its own advantages and disadvantages. The different sources of biomass lignin should be selected objectively according to its compositional structure, so as to achieve efficient biomass lignin depolymerization. In addition, the challenges and future development prospects of biomass lignin depolymerization were also discussed.