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Lignin Conversion to Value-Added Small-Molecule Chemicals : Towards Integrated Forest Biorefineries

Abdelaziz, Omar Y. LU (2021)
Abstract
Lignin is the most abundant aromatic biopolymer on Earth and has significant potential as a feedstock for industrial use. Due to its intrinsic heterogeneity and recalcitrance, lignin has been regarded as a low-value side-product in the pulp and paper industry and in second-generation biorefineries. However, novel technologies are currently being explored to utilize lignin as a renewable resource for bio-based chemicals, fuels, and materials. The efficient valorization of lignin would also improve the economics and sustainability of forest-based industries. Deriving value from lignin, beyond low-value heat and power, is thus essential for the success of a global circular bioeconomy employing lignocellulosic biomass as a raw... (More)
Lignin is the most abundant aromatic biopolymer on Earth and has significant potential as a feedstock for industrial use. Due to its intrinsic heterogeneity and recalcitrance, lignin has been regarded as a low-value side-product in the pulp and paper industry and in second-generation biorefineries. However, novel technologies are currently being explored to utilize lignin as a renewable resource for bio-based chemicals, fuels, and materials. The efficient valorization of lignin would also improve the economics and sustainability of forest-based industries. Deriving value from lignin, beyond low-value heat and power, is thus essential for the success of a global circular bioeconomy employing lignocellulosic biomass as a raw material.
This thesis discusses the possibility of producing high-value chemicals from technical lignin streams via thermochemical–biological methods. The work deals with four major research themes: (1) providing insights into the physicochemical properties of technical lignins that could be valuable in designing routes for their valorization, (2) developing technologies for the thermochemical depolymerization of lignin under batch and continuous-flow conditions, (3) developing strategies for the biological valorization of lignin by combining thermochemical depolymerization with microbial conversion, and (4) assessing the techno-economic viability of lignin as a feedstock for sustainable chemical production in a biorefinery.
Comprehensive physicochemical characterization of technical lignins is crucial in the development of molecularly tailored lignin-based applications. Elucidating the structural and compositional features can facilitate the matching of technical lignin streams with suitable valorization strategies, including thermochemical depolymerization. Two thermochemical depolymerization approaches were investigated for the production of low-molecular-weight aromatics from technical lignin: base-catalyzed depolymerization and oxidative depolymerization. Both approaches were also found to be effective means of pretreatment enabling the microbial conversion of kraft lignin.
Continuous processing allowed hydrothermal lignin treatment at exceptionally short residence times, and this is anticipated to be an important stepping-stone toward technical lignin valorization. Membrane filtration appeared to be a practical method of separating complex depolymerized lignin mixtures for product fractionation and upgrading. Bimetallic catalyst systems based on Cu, Mn, and V improved the oxidative conversion of lignosulfonate and kraft lignins into value-added aromatic compounds. Techno-economic analysis underlined the viability of large-scale chemical production from kraft lignin by oxidative depolymerization, offering opportunities for process integration with traditional pulp mills. (Less)
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author
supervisor
opponent
  • Dr. Gosselink, Richard, Wageningen Food & Biobased Research, The Netherlands.
organization
publishing date
type
Thesis
publication status
published
subject
keywords
aromatic monomers, biorefinery, catalysis, kraft lignin, lignin depolymerization, lignin valorization, microbial conversion, renewable chemicals, techno-economic analysis
pages
169 pages
publisher
Department of Chemical Engineering, Faculty of Engineering (LTH), Lund University
defense location
Lecture hall KC:B, Kemicentrum, Naturvetarvägen 14, Faculty of Engineering LTH, Lund University, Lund.
defense date
2021-03-15 09:00:00
ISBN
978-91-7422-783-3
978-91-7422-782-6
language
English
LU publication?
yes
id
6988edf0-0e7c-401f-9461-1a02757582fa
date added to LUP
2021-02-15 08:37:15
date last changed
2021-04-01 16:49:33
@phdthesis{6988edf0-0e7c-401f-9461-1a02757582fa,
  abstract     = {Lignin is the most abundant aromatic biopolymer on Earth and has significant potential as a feedstock for industrial use. Due to its intrinsic heterogeneity and recalcitrance, lignin has been regarded as a low-value side-product in the pulp and paper industry and in second-generation biorefineries. However, novel technologies are currently being explored to utilize lignin as a renewable resource for bio-based chemicals, fuels, and materials. The efficient valorization of lignin would also improve the economics and sustainability of forest-based industries. Deriving value from lignin, beyond low-value heat and power, is thus essential for the success of a global circular bioeconomy employing lignocellulosic biomass as a raw material.<br/>This thesis discusses the possibility of producing high-value chemicals from technical lignin streams via thermochemical–biological methods. The work deals with four major research themes: (1) providing insights into the physicochemical properties of technical lignins that could be valuable in designing routes for their valorization, (2) developing technologies for the thermochemical depolymerization of lignin under batch and continuous-flow conditions, (3) developing strategies for the biological valorization of lignin by combining thermochemical depolymerization with microbial conversion, and (4) assessing the techno-economic viability of lignin as a feedstock for sustainable chemical production in a biorefinery.<br/>Comprehensive physicochemical characterization of technical lignins is crucial in the development of molecularly tailored lignin-based applications. Elucidating the structural and compositional features can facilitate the matching of technical lignin streams with suitable valorization strategies, including thermochemical depolymerization. Two thermochemical depolymerization approaches were investigated for the production of low-molecular-weight aromatics from technical lignin: base-catalyzed depolymerization and oxidative depolymerization. Both approaches were also found to be effective means of pretreatment enabling the microbial conversion of kraft lignin.<br/>Continuous processing allowed hydrothermal lignin treatment at exceptionally short residence times, and this is anticipated to be an important stepping-stone toward technical lignin valorization. Membrane filtration appeared to be a practical method of separating complex depolymerized lignin mixtures for product fractionation and upgrading. Bimetallic catalyst systems based on Cu, Mn, and V improved the oxidative conversion of lignosulfonate and kraft lignins into value-added aromatic compounds. Techno-economic analysis underlined the viability of large-scale chemical production from kraft lignin by oxidative depolymerization, offering opportunities for process integration with traditional pulp mills.},
  author       = {Abdelaziz, Omar Y.},
  isbn         = {978-91-7422-783-3},
  language     = {eng},
  month        = {02},
  publisher    = {Department of Chemical Engineering, Faculty of Engineering (LTH), Lund University},
  school       = {Lund University},
  title        = {Lignin Conversion to Value-Added Small-Molecule Chemicals : Towards Integrated Forest Biorefineries},
  url          = {https://lup.lub.lu.se/search/ws/files/94244794/AbdelazizOY_PhDthesis_2021.pdf},
  year         = {2021},
}