(127b) Glycerol-Derived Compounds As Bio-Based Solvents for Organosolv Pulping of Lignocellulosic Biomass

Lignocellulose is a highly-abundant, renewable bio-composite derived from plant tissues and has drawn significant scientific attention as a feedstock for “green” chemicals and materials. Lignocellulose is comprised of three major biomacromolecules: cellulose (40 – 60 %), hemicellulose (10 – 40 %) and lignin (15 – 30 %). Historically, chemical pulping (e.g., kraft) of lignocellulose has followed “cellulose-first” approaches that prioritize procuring cellulosic fractions. During kraft pulping, macromolecular lignins are degraded into smaller, alkaline-soluble species that form “black” liquors, which are incinerated to generate low-grade heat and recoup pulping chemicals. Nevertheless, lignins are the most abundant, biogenic source of aromatic chemicals and their valorization into value-added products could enhance the economic viability of biorefineries.

“Lignin-first” biorefining is facilitated by organosolv pulping, a solvothermal process (100-250 °C) that applies organic solvents and chemical additives to extract lignins (50-90 wt%). However, organosolv pulping has been commercialized sparingly due to volatile organic solvents necessitating specialized, high-pressure equipment (10-35 bar). Glycerol-derived compounds (GDCs) are a new class of biobased solvents synthesized from glycerol, an ample and inexpensive byproduct of the biodiesel industry. GDCs possess tailorable molecular structures and solvent properties (e.g., high boiling points). As such, GDCs constitute a new class of organosolv solvents that promote lignin-first biorefining.

The present study investigates GDC organosolv pulping under mild conditions for extracting lignins. The influence of GDC structure, additives, and process conditions (e.g., temperature, time) on the biorefining of lignocellulose into cellulose and lignin product fractions are evaluated. Physical and chemical phenomena governing GDC organosolv pulping of lignocellulosic biomass are elucidated through characterization of cellulose and lignin product fractions by a suite of wet chemistry, spectroscopic, and microscopic methodologies. The outcomes of the present investigation advance the development of environmentally-cogent and scalable organosolv processes for valorizing lignocellulose into feedstocks for value-added, biobased materials.