Electrochemistry of Biomass-Derived Materials I. Characterization, Practionation, and Reductive Electrolysis of Ethanol-Extracted Explosively-Depressurized Aspen Lignin
作者:
HelenaL. Chum,
M. Ratcliff,
H.A. Schroeder,
D.W. Sopher,
期刊:
Journal of Wood Chemistry and Technology
(Taylor Available online 1984)
卷期:
Volume 4,
issue 4
页码: 505-532
ISSN:0277-3813
年代: 1984
DOI:10.1080/02773818408070665
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
The chemical characterization (functional group distribution) and spectroscopic properties (13C,1H, IR, UV-Vis) of a number of lignins obtained from ethanol extraction of explosively-decompressed aspen (Populus tremuloides) lignin (EEEDAL) are described. In this process mod is heated to ∼240°C by direct steam and fiberized by sudden decompression. Both mechanical and chemical degradation occur which lead to a decrease of the molecular weight of all of the natural polymers. The lignin fraction is soluble in alcohols; it has a low number average molecular weight (925) and is very reactive. EEEDAL was subjected to fractionation by differential solubility prior to and after electrolyses on mercury cathodes at −2.6 V vs. Ag/AgCl in methanol/tetraethyl-ammonium perchlorate. After recovery of 85–90% of the original weight of material used by precipitation with acid, followed by a series of extractions, the chemical and spectroscopic properties of each fraction were determined. The acid-insoluble fractions are more condensed than the acid-soluble fractions and have lower phenolic OH and lower aliphatic OH contents than the acid-soluble fractions. The acid-soluble fractions phenolic OH content approaches one per phenylpropane (5) unit of the Lignin. Electrolyses increase the amount of lower molecular weight, high phenolic content, acid-soluble lignins and changes the molecular weight distribution by decreasing the polydispersity of the resulting lignins. These low-molecular-weight lignins are chemically reactive (for instance, with formaldehyde) and can be used in the partial replacement of phenol in phenol-formaldehyde thermosetting resins.
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