Preparation of aerogels from wheat straw lignin by cross-linking with oligo(alkylene glycol)-α,ω-diglycidyl ethers

• Lignin from Liquid Hot Water pretreatment was used as building block for aerogels.
• Lignin was crosslinked using oligo(alkylene glycol)-α,ω-diglycidyl ethers.
• Density (ρ) and surface area (A) varied with lignin and crosslinker concentration.
• Lowest ρ = 0.15 g cm−3, highest A = 120 m2 g−1 and thermal conductivity 50 mW m−1 K−1.

Lignin is one of the most abundant by-products of pulp and paper manufacturing and second-generation biorefineries. Presently it is mainly used for energy production, but it is evident that higher added-value utilization options would be beneficial. One possible process is to use lignin as building block for chemical synthesis. In this work, lignin was used as a raw material for the production of aerogels as special class of porous materials. Lignin obtained from Liquid Hot Water (LHW) pretreatment of wheat straw has been cross-linked with oligo(ethylene glycol)- and oligo(propylene glycol)-α,ω-diglycidyl ethers of varying length, aiming at the preparation of lignin-based hydrogels and their conversion to aerogels. The effect of cross-linking conditions, such as lignin concentration, cross-linker-to-lignin ratio, gelation temperature and solvent exchange conditions, on the textural properties of the resulting aerogels were studied. The obtained aerogels had a surface area of up to 120 m2 g−1, bulk density as low as 0.15 g cm−3 and a thermal conductivity of about 50 mW m−1 K−1.

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