Thermal conversion of lignin to phenols: Relevance between chemical structure and pyrolysis behaviors

Abstract

In this study, the Fourier transform infrared (FTIR) spectrometry and the 13 C-1 H correlation two-dimensional (2D) heteronuclear single-quantum coherence (HSQC) nuclear magnetic resonance (NMR) were introduced to determine the chemical structure of soda alkali lignin (SAL) and Alcell organosolv lignin (AOL), and the relevance between chemical structure and pyrolysis behaviors was evaluated by thermogravimetric analysis (TGA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Results showed that the two lignin samples had similar functional groups and S/G ratio, excepting side-chain linkages. SAL was mainly cross-linked by β-β' linkages, while the main linkage within AOL was β-O-4'. This difference proposed that AOL had the worse thermal stability and was easier to be pyrolyzed to phenols than SAL. Herein, the pyrolysis transformation of SAL was always promoted by the increased temperature, whereas the generated phenols from AOL would be redecomposed at high pyrolysis

Metal Ion‐Catalyzed Hydrothermal Liquefaction of Calcium Lignosulfonate in Subcritical Water

“…1 and summarized in Tab. S1 in the Supporting Information, typical absorptions of lignin structure were clearly recognized, including O-H stretching vibration (peak 1), C-H stretching vibration in methyl and methylene groups (peaks 2 and 3), aromatic skeletal vibrations (peaks 4, 5, and 7), and aromatic ring breathing (peak 8) [29]. In addition, peak 9 (1042 cm -1 ) and peak 10 (652 cm -1 ) were assigned to the absorptions of S-O bonds [30,31], which benefited from the sulfonic groups.…”

“…This suggested that the neutral-alkaline condition was more favorable as compared to acid condition. Lignin is composed of three typical building units: p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) units [12,29,38]. Therefore, these phenolic monomers degraded from lignin under subcritical condition had the three different aromatic units.…”

Recovery and Utilization of Lignin Monomers as Part of the Biorefinery Approach

“…Pyrolysis is viewed as one of the most promising thermochemical technologies for lignin utilization [191,192]. The main compounds produced from lignin during fast pyrolysis are gaseous hydrocarbons (i.e., CO2, CO), volatile liquids (methanol, acetone and acetaldehyde), monolignols, monophenols (phenol, guaiacol, syringol, and catechol) and other monosubstituted phenols [188].…”

Catalytic Depolymerization of Alkali Lignin in Sub- and Super-critical Ethanol

“…(Pandey and Kim 2011;Wang et al 2013;Peng et al 2014;Liu et al 2016). However, the authors' previous research (Guo et al 2014(Guo et al , 2017 indicated that the phenols yields obtained from alkali lignin pyrolysis were approximately 60% liquid oil, while the solid product yield also reached 30%.…”