Research progress on mechanism and methods of lignin separation
Lignin can be used to obtain many kinds of fuels,chemicals and materials through rational processing and conversion.Extracting lignin by gentle method is the premise of realizing the high value utilization of lignin.In this paper,the separation methods and research progress of lignin in recent years are reviewed,with emphasis on the separation mechanism of various separation methods and the composition and structure characteristics of lignin.The advantages and disadvantages,applicability and industrial application of different separation methods are summarized.Acid method promotes the hydrolysis of ether bond in polysaccharide polymer to depolymerize hemicellulose and cellulose.Alkali method mainly cracks the ether and ester bond between lignin and carbohydrate.Acid method and alkali method are mature as traditional lignin separation methods,but they are easy to cause the self-polymerization of lignin.Organic solvent method mainly destroys the β-aryl ether bond,and its separation condition is mild,which can better retain the original structure and reactivity of lignin.New green solvent systems such as ionic liquid and deep eutectic solvent have dual functions of solvent and reaction medium,and have received extensive attention.The coupling of separation methods and the assistance of physical,chemical or biological technology will play an important role in optimizing the separation process of lignin and exploring the high-value utilization of lignin.