@Article{jrm.2023.025279,
AUTHOR = {Penghui Li, Zhengwei Jiang, Chi Yang, Jianpeng Ren, Bo Jiang, Wenjuan Wu},
TITLE = {Degradation of Alkaline Lignin in the Lactic Acid-Choline Chloride System under Mild Conditions},
JOURNAL = {Journal of Renewable Materials},
VOLUME = {11},
YEAR = {2023},
NUMBER = {5},
PAGES = {2233--2248},
URL = {http://www.techscience.com/jrm/v11n5/51700},
ISSN = {2164-6341},
ABSTRACT = {Lignin is a natural polymer, second only to cellulose in natural reserves. Degradation is one of the ways to achieve
the high-value transformation of lignin. Deep eutectic solvent (DES) thermal degradation of lignin can be used as
an excellent green degradation method. This paper introduces the degradation mechanism and effect of the lactic
acid-choline chloride DES system in dissolving and degrading alkaline lignin, and the final solvent recovery. It can
also be found from the scanning electron microscope (SEM) images that the surface of the degraded solid product
is transformed from smooth to disordered. Fourier transform infrared (FTIR) spectroscopy and <sup>1</sup>
H-NMR spectroscopy were used to characterize the changes in lignin functional groups during DES treatment. The results
showed that the content of phenolic hydroxyl groups increased after degradation, indicating that the β-O-4 ether
bond was broken. The molecular weight of the degraded lignin was observed by gel permeation chromatography
(GPC), and the lignin residue with low molecular weight and narrow polydispersity index was obtained. The lowest average molecular weight (Mw) reached 2512 g/mol. The ratio of oxygen to carbon atoms in lignin increased
substantially during degradation as measured by X-ray photoelectron spectroscopy (XPS), probably because DES
treatment was accompanied by many oxidation reactions, which led to significant structural changes in lignin and
a large number of ether bond breakage reactions during the reaction. The main final degradation products are
aromatic monomers, vanillin, butyrovanillone, etc.},
DOI = {10.32604/jrm.2023.025279}
}