Publication
Title
Selective C(aryl)-O bond cleavage in biorenewable phenolics
Author
Abstract
Biorefining of lignocellulosic biomass via a lignin first approach delivers a range of products with high oxygen content. Besides pulp, a lignin oil rich in guaiacols and syringols is obtained bearing multiple C(aryl)-OH and C(aryl)-OMe groups, typically named phenolics. Similarly, technical lignin can be used but is generally more difficult to process providing lower yields of monomers. Removal of the hydroxy and methoxy groups in these oxygenated arenes is challenging due to the inherently strong C-O bonds, in addition to the steric and electronic deactivation by adjacent -OH or -OMe groups. Moreover, chemoselective removal of a specific group in the presence of other similar functionalities is non-trivial. Other side-reactions such as ring saturation and transalkylation further complicate the desired reduction process. In this overview, three different selective reduction reactions are considered. Complete hydrodeoxygenation removes both hydroxy and methoxy groups resulting in benzene and alkylated derivatives (BTX type products) which is often complicated by overreduction of the arene ring. Hydrodemethoxylation selectively removes methoxy groups in the presence of hydroxy groups leading to phenol products, while hydrodehydroxylation only removes hydroxy groups without cleavage of methoxy groups giving anisole products. Instead of defunctionalization via reduction transformation of C(aryl)-OH, albeit via an initial derivatization into C(aryl)-OX, into other functionalities is possible and also discussed. In addition to methods applying guaiacols and syringols present in lignin oil as model substrates, special attention is given to methods using mixtures of these compounds obtained from wood/technical lignin. Finally, other important aspects of C-O bond activation with respect to green chemistry are discussed. Selective removal of the hydroxy, methoxy or both groups in biorenewable oxygenated arenes (derived from lignin depolymerization) provides, respectively, anisoles, phenols and benzenes.
Language
English
Source (journal)
Chemical Society reviews. - London
Publication
Cambridge : Royal soc chemistry , 2024
ISSN
0306-0012
DOI
10.1039/D3CS00570D
Volume/pages
(2024) , p. 1-63
ISI
001204799300001
Pubmed ID
38634517
Full text (Publisher's DOI)
UAntwerpen
Faculty/Department
Research group
Project info
Sustainable reduction reactions in water via in situ hydrogen gas production.
Next generation lignocellulosics biorefinery concepts and implementation (Next-BIOREF).
Selective sustainable hydrodeoxygenation of bioaromatics (Selective HDO).
Publication type
Subject
Affiliation
Publications with a UAntwerp address
External links
Web of Science
Record
Identifier
Creation 02.05.2024
Last edited 16.05.2024
To cite this reference