AEROGELS FROM LIGNIN OBTAINED BY LIQUID-HOT-WATER TREATMENT OF WHEAT STRAW

摘要

Aerogels can be principally synthesized from any material that can form a gel. This includes natural organic polymers, such as starch, alginate, cellulose, and other polysaccharides, which have a clear advantage of being biocompatible, biodegradable and renewable. The aim of this work is to apply this technique to lignin, another biopolymer but of phenolic nature, in order to obtain aerogels. Lignin is a natural polymer found in lignocellulosic material and represents the largest by-product in the manufacturing of lignocellulose-based ethanol. The lignin used in this work was obtained after enzymatic saccharification of liquid-hot-water-pretreated wheat straw from a second generation biorefinery. This phenolic biopolymer has been used as a renewable and biodegradable organic backbone for the production of porous materials. Due to its highly branched, three dimensional structure, lignin can form a colloidal solution with the appropriate selection of a crosslinker. In this work, alkaline aqueous solutions of lignin were chemically crosslinked with oligooxyalkylene diglycidylethers of different chain length and dried under scCO_2 after solvent exchange. The porous materials obtained in this way exhibit high surface area, high porosity, small density and good mechanical properties, which allow their use in different industrial applications, such as a natural product based insulation material, due to their relatively low thermal conductivity, which lies around the higher end of common insulation materials.