Influence of the biomass-source and the extraction process on lignin properties and γ-valerolactone induced conversion of biomass towards valuable lignin monomers

Abstract

With a rising demand in fossil-based chemicals and their derived products, alternatives have to be developed from bio-based materials to meet the declining fossil resources. Lignocellulosic biomass is widely seen as a promising alternative, especially on the topic of bioplastics. However, challenges still lie in complete and efficient valorization of biomass and converting its components into suitable products. For this purpose, the tailoring of the lignin structure through extraction method and choice of biomass have to be studied extensively. The green solvent γ-valerolactone (GVL) was shown to facilitate efficient fractionation of all main components of lignocellulosic biomass in our previous study. To further build on this process of a GVL-based extraction process at mild conditions, lignin from different process conditions and biomass types was extracted, and subsequent hydrogenolysis experiments were conducted to decompose especially lignin oligomers with high ether contents into specific monomers. The structure of the products, referring to lignin oligomers and monomers, largely depends on the biomass type of origin of the lignin and the extraction process. The product characteristics from several biomass sources were analyzed using NMR spectroscopy, UV/Vis spectroscopy, and chromatography techniques. Default extracted lignin and lignin extracted with an aldehyde-assisted process led to a broad spectrum of lignin with different properties, indicating the influence of the extraction process on the extracted lignin properties. The present study examines the production of lignin oligomers and monomers with different properties from lignocellulosic biomass after two different selective extraction and decomposition processes using the green solvent GVL. These products can be used for different applications depending on their post-extraction properties that originate from its biomass source and the extraction/degradation process.