(72h) Sustainable Thermochemical Extraction of Lignins with Glycerol-Derived Solvents

Glycerol organosolv (GO) processing of lignocellulosic biomass has emerged as a thriving area of research in the last few decades to extract and isolate lignins. A byproduct of the biodiesel industry, glycerol is abundant, renewable, non-toxic, and not volatile, which has made it an eco-friendly and cost-effective solvent for biomass pretreatment. Also, various types of glycerol with various amounts of impurities have been explored for the fractionation of different kinds of biomass. However, glycerol is difficult to work with due to its very high viscosity. Hence, derivatizing glycerol present great opportunities for tuning the properties of glycerol and solving the issues associated with viscosity. Such glycerol-derived compounds (GDCs), especially glycerol ethers, present low toxicity and have been explored as solvents for carbon capture and polymer dissolution. Pine is a commercially grown softwood, and several varieties are amongst the most abundant type of terrestrial biomass in the Southeast US, with some estimating up to 40 million pine trees within the region. For more sustainable use of these vast biomass resources which will help boost the economy of the region, suitable solvents for pretreatment must be given priority and that is where these glycerol ethers could present great opportunities for extracting lignins from lignocellulosic biomass.

Hence, we tested different glycerol ethers for effectiveness in the extracting lignins from lignocellulosic biomass under relatively mild conditions (120 ⁰C ≤ T ≤180 ⁰C, 10 min < t ≤ 60 min). Sulfuric and acetic acid additives were applied in dilute concentrations (C≤40 mN). Lignin and some hemicellulose were dissolved in the solvents, and pulp residues were enriched with cellulose. Dissolved lignins were precipitated by simple aqueous, antisolvent precipitation. Using state-of-the-art analytical tools comprising microscopic, spectroscopic, x-ray diffraction methods, we analyzed the cellulose pulp fibers as well as the lignin-precipitates to elucidate the impact of reaction conditions on the cellulose pulp and lignin produced.