Efficient Green Pre-Treatment of Coniferous Biomass Using Alkali-Assisted Deep Eutectic Solvents for Tall Oil Production and Lignin Component Separation

Abstract

With the growing global energy demand due to population expansion and industrial development, the efficient valorization of plant resources is critical for achieving carbon neutrality and carbon conversion. While significant progress has been made in the comprehensive utilization of lignocellulosic biomass through various novel pre-treatment methods, using lignocellulosic materials as raw materials to separate lipids while separating the three main components, especially from lipid-rich coniferous trees, still faces many challenges. This article presents a novel pre-treatment approach using alkali-assisted deep eutectic solvents (DES) in combination with the tall oil production process derived from sulfite pulping by-products, focusing on the production of tall oil and lignin components from black liquor. The results indicate that the optimal acidification conditions are a pH of 6 and a reaction time of 120 minutes at high temperature, yielding the best crude tall oil with linoleic acid at 79.9%, isoabietic acid at 28.5%, and dehydroabietic acid at 32.3%. Under weak acidic conditions, some lignin is affected by high temperatures, leading to the formation of small lignin fragments. However, under the protection of DES, a large amount of β-O-4 bonds is still preserved, which is beneficial for subsequent degradation. This newly designed pre-treatment process for biomass raw materials offers valuable guidance for achieving efficient green defatting and separation of the three main components of lignocellulosic materials.

Keywords: Tall oil, Deep eutectic solvent (DES), Alkali-assisted, Fractionation, Lignocellulosic material