Supercritical Water-induced Lignin Decomposition Reactions: A Structural and Quantitative Study

Abstract

The use of supercritical water for the decomposition of lignin and evaluation of its influence on lignin decomposition and conversion to various products was the thrust of the current study. Poplar alkali lignin (AL), corncob-to-xylitol residue lignin (XRL), and cornstalk-to-ethanol residue lignin (ERL) were the lignin species studied because they constitute the main residual lignins available in the biomass refinery industry. The lignins were characterized by elementary analysis, Fourier transform infrared spectrometry (FT-IR), phosphorus nuclear magnetic resonance ( 31 P-NMR), and X-ray diffraction (XRD), and their hydrothermal depolymerization products were analyzed by gas chromatography-mass spectrometer (GC-MS). The results showed that the residual lignin is a potential source for valuable aromatics. The XRL had the best total phenolics yield, 140 mg/g, while AL had the lowest, 90 mg/g. The maximum yields of phenol (28.94 mg/g) and 4-ethylphenol (36.21 mg/g) were obtained from XRL depolymerization at 375 °C for 30 min, and the optimal yields of guaiacol (14.34 mg/g) and 2,6-dimethoxyphenol (15.67 mg/g) were achieved by AL at 375 °C for 30 min. The information here provides some insights toward developing selective biorefinery methods for lignin-to-organic products conversion processes.

Deep Eutectic Solvents (DESs) for the Isolation of Willow Lignin (Salix matsudana cv. Zhuliu)

“…As shown in Table 5 , the DES-Lignin extracted from willow could be recognized as GHS lignin, and the G:H:S ratio was 2.59:1:4.73, indicating that the syringyl unit was dominant in DES-Lignin, which was consistent with the typical structure of hardwood lignin. It was interesting that the content of the total phenol hydroxyl group in DES-Lignin (0.915 mmol·g −1 ) was higher than that of poplar alkali lignin (AL) or other biorefinery lignins [ 37 ], suggesting that the DES-lignin had a higher potential reactivity.…”

Characterization of Wood-based Industrial Biorefinery Lignosulfonates and Supercritical Water Hydrolysis Lignin

“…There are three pathways to create value-added products from lignin: (i) Due to the large amounts of aromatic structures present in lignin, it can be depolymerized into aromatic or platform chemicals. Fragmentation of lignin into smaller aromatic compounds offers a significant market potential, but it is less developed than the use of lignin as a macromolecule [21]. (ii) Lignin as an unchanged macromolecule is used as additive or polymer blend [2].…”

Sequential fractionation of lignin-derived pyrolysis oil via extraction with a combination of water and organic solvents

“…Lignocellulosic biomass is a vital raw material for the sustainable production of fuels, chemicals, and energy. It consists of three major biopolymers that are ubiquitous in nature (Jiang et al 2016). Among those biopolymers, lignin is the second largest component of lignocellulosic biomass, accounting for 15% to 30% of the mass, and it is generally considered to be composed of three phenylpropane units.…”