Biphasic Separation Approach in the DES Biomass Fractionation Facilitates Lignin Recovery for Subsequent Valorization to Phenolics

Abstract

Herein, we demonstrate a sustainable technique for quality facile lignin recovery by adopting a biphasic separation approach during the deep eutectic solvent (DES) disintegration of biomass for subsequent valorization. The tetrahydrofuran (THF)/ aq NaCl combination influenced the attainment of biphasic layer separation, consequently accelerating the movement of DESsolubilized lignin to the organic phase and allowing for the easy recovery of lignin and solvents (both THF and DES) for reuse. The modified protocol facilitated ∼32% wt lignin per wt of sawdust with a 95% purity (based on a Klason analysis), which was nearly 88% of the lignin extracted to the potential lignin of sawdust. This was achieved through the fractionation of sawdust using a choline chloride and lactic acid combination at a 1:2 molar ratio under modest thermal conditions. The obtained results were ∼2-fold higher than those of the conventional DES protocol, employing the H 2 O−EtOH mixture for lignin precipitation using a similar wood substrate. All of the analytical characterization techniques, including 13 C NMR, Fourier transform infrared, gel permeation chromatography, and pyrolysis-gas chromatographymass spectrometry (Py-GC/MS), established the relevant structural and morphological characteristics, making the resultant lignin an adequate feedstock for the potential production of aromatic chemicals because of the dominance of the β-O-4 content and the limited residual constituents, including sugars and silica. Upon evaluating its suitability for phenolic chemical synthesis via hydrogenolysis, a ∼48% butylated hydroxytoluene yield was obtained as a dominant phenolic product over heterogeneous Ru@ V 2 O 5 . Overall, the findings indicated that DES is proficient in fractionating lignocellulose for the entire release of lignin (>90%). The maximum recovery of the released lignin was attributed to the superlative performance of the novel THF/aq NaCl combination through the influence of molecular interactions, such as hydrogen bonding and dipole−dipole interactions between the lignin and solvent, thereby establishing an alternative trend for quality lignin extraction for deriving phenolics.

Deep Eutectic Solvents for the Valorisation of Lignocellulosic Biomasses towards Fine Chemicals

“…FF is an important, renewable platform chemical from hemicelluloses, is considered to be one of the platform chemicals with the highest potential and can be used in many industrial fields. The yield of FF in the DES/MIBK biphasic system was much higher than that of the AlCl 3 -catalyzed hydrothermal pretreatment of Eucalyptus, in which the yield of FF was only 17.85% [91]. The optimum pretreatment conditions were 140 • C for 90 min, the maximum yield of FF registered was 70.3% and the maximum saccharification was 80.8%, which was much higher than that evaluated for the raw material.…”

Deep eutectic-like solvents: Promising green media for biomass treatment and preparation of nanomaterials

“…Among the rest, the potential of using the DESs as a green medium in biomass treatment and transformation is vast. That is to say, DESs can react with biomass, which can lead to the transformation (Majová et al 2017;Tian et al 2022), fractionation (Chen and Wan 2018), separation (Loow et al 2017;Kumar et al 2020), and modification (Smirnov et al 2020;Douard et al 2021) of biomass components. The separation of the main components -lignin and cellulose has been extensively studied (Smirnov et al 2020;Douard et al 2021).…”

Deep eutectic-like solvents: Promising green media for biomass treatment and preparation of nanomaterials

“…Among the rest, the potential of using the DESs as a green medium in biomass treatment and transformation is vast. That is to say, DESs can react with biomass, which can lead to the transformation (Majová et al 2017;Tian et al 2022), fractionation (Chen and Wan 2018), separation (Loow et al 2017;Kumar et al 2020), and modification (Smirnov et al 2020;Douard et al 2021) of biomass components. The separation of the main componentslignin and cellulose has been extensively studied (Smirnov et al 2020;Douard et al 2021).…”