From lignin to chemicals: Hydrogenation of lignin models and mechanistic insights into hydrodeoxygenation via low-temperature C-O bond cleavage
File(s)
Accepted version
Author(s)
Type
Journal Article
Abstract
The catalytic hydrogenation of a series of lignin model compounds, including anisole, guaiacol, 1,2-dimethoxybenzene, 4-propyl-2-methoxyphenol, and syringol, has been investigated in detail, using a Ru/C catalyst in acetic acid as the solvent. Both hydrogenation of the aromatic unit and C–O bond cleavage are observed, resulting in a mixture of cyclohexanes and cyclohexanols, together with cyclohexyl acetates due to esterification with the solvent. The effect on product composition of the reaction parameters temperature (80–140 °C), pressure (10–40 bar), and reaction time (0.5–4 h) has been evaluated in detail. The lignin model compound 4-propyl-2-methoxyphenol was converted to 4-propylcyclohexanol in 4 h at 140 °C and 30 bar of H2 pressure with 84% conversion and 63% selectivity. Mechanistic studies on the reactivity of reaction intermediates have shown that C–O bond cleavage under these relatively mild conditions does not involve a C–O bond hydrogenolysis reaction but is due to elimination and hydrolysis reactions (or acetolysis in acetic acid solvent) of highly reactive cyclohexadiene- and cyclohexene-based enols, enol ethers, and allyl ethers.
Date Issued
2019-03-01
Date Acceptance
2019-01-01
Citation
ACS Catalysis, 2019, 9 (3), pp.2345-2354
ISSN
2155-5435
Publisher
American Chemical Society
Start Page
2345
End Page
2354
Journal / Book Title
ACS Catalysis
Volume
9
Issue
3
Copyright Statement
© 2019 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Catalysis, after peer review and technical editing by the publisher. To access the final edited and published work see https://dx.doi.org/10.1021/acscatal.8b04714
Sponsor
Engineering & Physical Science Research Council (EPSRC)
The Coca-Cola Company
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000460600600067&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Grant Number
EP/K014676/1
4504238214
Subjects
Science & Technology
Physical Sciences
Chemistry, Physical
Chemistry
lignin
hydrogenation
hydrogenolysis
ruthenium
biomass
hydrodemethoxylation
AQUEOUS-PHASE HYDROGENATION
TEREPHTHALIC ACID
ACETIC-ACID
BIO-OIL
SELECTIVE HYDROGENATION
HETEROGENEOUS CATALYSTS
RU-H2O SYSTEM
VINYL ETHERS
PH DIAGRAM
BIOMASS
Publication Status
Published
Date Publish Online
2019-01-25