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Lignin for Energy, Chemicals and Materials II
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Lignin for Energy, Chemicals and Materials II

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Materials Chemistry".

Deadline for manuscript submissions: closed (31 August 2021) | Viewed by 15875

Special Issue Editor

Dr. Claudio Gioia

E-Mail Website
Guest Editor
Department of Civil, Chemical, Environmental and Materials Engineering, Alma Mater Studiorum, University of Bologna, Via Terracini 28, 40131 Bologna, Italy
Interests: biobased monomers; polymers from renewable resources; chemical modification of lignocellulosic compounds; lignin based thermosetting resins; chemical valorization of food waste for the production of bio-materials

Special Issue Information

Dear Colleagues,

Lignin is the second most abundant natural renewable polymer after cellulose. It is currently being produced in large quantities as a byproduct of chemical pulping and cellulosic ethanol processes. According to the International Lignin Institute, about 40–50 million tons of Kraft lignin (KL) are generated each year, globally, in the form of “black liquor”. While combustion of black liquor to regenerate pulping chemicals and to produce steam and power is an integral part of the Kraft process, a small portion of lignin can be removed without compromising mill material and energy balances. Meanwhile, the production of ethanol, butanol, and platform chemicals (e.g., lactic, succinic and other organic acids) from cellulosic sugars is growing. For this to achieve extensive commercial success on a worldwide basis, value-added applications are needed for the hydrolysis lignin byproducts that are generated from lignocellulose hydrolysis processes.

Many studies have been conducted on lignin utilization. Similar to other carbonaceous solid fuels, lignin can be a source for energy and fuels (e.g., combustion/co-combustion of lignin for energy, pyrolysis or hydrothermal liquefaction of lignin for bio-oils/liquid biofuels, or gasification of lignin for syngas/hydrogen). The presence of various functional groups (aromatic ring-free positions and hydroxyl groups) on lignin structure, biodegradability, antioxidant, flame retardance, and reinforcing capability make it a potential candidate for the production of bio-aromatic chemicals (e.g., vanillin, phenols and antioxidants), bio-based polymeric materials (e.g., resins and polymers), and carbon fibers for use as reinforcement fillers in thermoplastic polymers, lightweight composite materials, as well as graphene for use in supercapacitors for energy storage. Direct use of lignin for chemical synthesis and materials is challenging due to the high molecular weight and chemical heterogeneity; however, depolymerization and fractionation processes are currently creating new opportunities and new applications. Additionally, the reactivity of lignin can be enhanced through chemical modifications introducing specific functional groups.

This Special Issue aims to cover recent progress and trends in the utilization of lignin or modified/depolymerized lignin in chemical synthesis, materials, and energy. Submissions are welcome but not limited to the topics listed below. Types of contributions to this Special Issue can be full research articles, short communications, and reviews focusing on the utilization of lignin for energy/fuels, chemical and materials.

  • Extraction of lignin from pulping processes or cellulosic ethanol processes;
  • Chemical modification/depolymerization of lignin;
  • Fractionation/purification of lignin;
  • Combustion/co-combustion of lignin for energy;
  • Pyrolysis or hydrothermal liquefaction of lignin for bio-oils/liquid biofuels;
  • Gasification of lignin for syngas/hydrogen;
  • Production of bio-aromatic chemicals from lignin (e.g., vanillin, phenols and antioxidants);
  • Synthesis of bio-based polymeric materials from lignin (e.g., resins and polymers);
  • Production of carbon fibers as reinforcement fillers in thermoplastic polymers or lightweight composite materials;
  • Production of graphene for use in supercapacitors for energy storage.

Dr. Claudio Gioia
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Lignin
  • Chemical characterization
  • Chemical modification
  • Depolymerization
  • Fractionation and purification
  • Combustion
  • Energy
  • Pyrolysis
  • Hydrothermal liquefaction
  • Bio-oils
  • Phenols
  • Bio-aromatic chemicals
  • Synthesis
  • Monomers
  • Resins
  • Polymers
  • Carbon fibers
  • Composites
  • Graphene
  • Supercapacitors

Published Papers (4 papers)

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Research

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19 pages, 8666 KiB  
Article
Pore Development during the Carbonization Process of Lignin Microparticles Investigated by Small Angle X-ray Scattering
by Harald Rennhofer, Janea Köhnke, Jozef Keckes, Johannes Tintner, Christoph Unterweger, Thomas Zinn, Karl Deix, Helga Lichtenegger and Wolfgang Gindl-Altmutter
Molecules 2021, 26(7), 2087; https://doi.org/10.3390/molecules26072087 - 06 Apr 2021
Cited by 8 | Viewed by 2294
Abstract
Application of low-cost carbon black from lignin highly depends on the materials properties, which might by determined by raw material and processing conditions. Four different technical lignins were subjected to thermostabilization followed by stepwise heat treatment up to a temperature of 2000 °C [...] Read more.
Application of low-cost carbon black from lignin highly depends on the materials properties, which might by determined by raw material and processing conditions. Four different technical lignins were subjected to thermostabilization followed by stepwise heat treatment up to a temperature of 2000 °C in order to obtain micro-sized carbon particles. The development of the pore structure, graphitization and inner surfaces were investigated by X-ray scattering complemented by scanning electron microscopy and FTIR spectroscopy. Lignosulfonate-based carbons exhibit a complex pore structure with nanopores and mesopores that evolve by heat treatment. Organosolv, kraft and soda lignin-based samples exhibit distinct pores growing steadily with heat treatment temperature. All carbons exhibit increasing pore size of about 0.5–2 nm and increasing inner surface, with a strong increase between 1200 °C and 1600 °C. The chemistry and bonding nature shifts from basic organic material towards pure graphite. The crystallite size was found to increase with the increasing degree of graphitization. Heat treatment of just 1600 °C might be sufficient for many applications, allowing to reduce production energy while maintaining materials properties. Full article
(This article belongs to the Special Issue Lignin for Energy, Chemicals and Materials II)
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10 pages, 1313 KiB  
Article
Lignin Precipitation and Fractionation from OrganoCat Pulping to Obtain Lignin with Different Sizes and Chemical Composition
by Dennis Weidener, Arne Holtz, Holger Klose, Andreas Jupke, Walter Leitner and Philipp M. Grande
Molecules 2020, 25(15), 3330; https://doi.org/10.3390/molecules25153330 - 22 Jul 2020
Cited by 6 | Viewed by 3340
Abstract
Fractionation of lignocellulose into its three main components, lignin, hemicelluloses, and cellulose, is a common approach in modern biorefinery concepts. Whereas the valorization of hemicelluloses and cellulose sugars has been widely discussed in literature, lignin utilization is still challenging. Due to its high [...] Read more.
Fractionation of lignocellulose into its three main components, lignin, hemicelluloses, and cellulose, is a common approach in modern biorefinery concepts. Whereas the valorization of hemicelluloses and cellulose sugars has been widely discussed in literature, lignin utilization is still challenging. Due to its high heterogeneity and complexity, as well as impurities from pulping, it is a challenging feedstock. However, being the most abundant source of renewable aromatics, it remains a promising resource. This work describes a fractionation procedure that aims at stepwise precipitating beech wood (Fagus sp.) lignin obtained with OrganoCat technology from a 2-methyltetrahydrofuran solution, using n-hexane and n-pentane as antisolvents. By consecutive antisolvent precipitation and filtration, lignin is fractionated and then characterized to elucidate the structure of the different fractions. This way, more defined and purified lignin fractions can be obtained. Narrowing down the complexity of lignin and separately valorizing the fractions might further increase the economic viability of biorefineries. Full article
(This article belongs to the Special Issue Lignin for Energy, Chemicals and Materials II)
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Review

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21 pages, 3390 KiB  
Review
Deconstruction of Lignin: From Enzymes to Microorganisms
by Jéssica P. Silva, Alonso R. P. Ticona, Pedro R. V. Hamann, Betania F. Quirino and Eliane F. Noronha
Molecules 2021, 26(8), 2299; https://doi.org/10.3390/molecules26082299 - 15 Apr 2021
Cited by 38 | Viewed by 5133
Abstract
Lignocellulosic residues are low-cost abundant feedstocks that can be used for industrial applications. However, their recalcitrance currently makes lignocellulose use limited. In natural environments, microbial communities can completely deconstruct lignocellulose by synergistic action of a set of enzymes and proteins. Microbial degradation of [...] Read more.
Lignocellulosic residues are low-cost abundant feedstocks that can be used for industrial applications. However, their recalcitrance currently makes lignocellulose use limited. In natural environments, microbial communities can completely deconstruct lignocellulose by synergistic action of a set of enzymes and proteins. Microbial degradation of lignin by fungi, important lignin degraders in nature, has been intensively studied. More recently, bacteria have also been described as able to break down lignin, and to have a central role in recycling this plant polymer. Nevertheless, bacterial deconstruction of lignin has not been fully elucidated yet. Direct analysis of environmental samples using metagenomics, metatranscriptomics, and metaproteomics approaches is a powerful strategy to describe/discover enzymes, metabolic pathways, and microorganisms involved in lignin breakdown. Indeed, the use of these complementary techniques leads to a better understanding of the composition, function, and dynamics of microbial communities involved in lignin deconstruction. We focus on omics approaches and their contribution to the discovery of new enzymes and reactions that impact the development of lignin-based bioprocesses. Full article
(This article belongs to the Special Issue Lignin for Energy, Chemicals and Materials II)
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17 pages, 6569 KiB  
Review
Characterization of Lignin Compounds at the Molecular Level: Mass Spectrometry Analysis and Raw Data Processing
by Ruochun Zhang, Yulin Qi, Chao Ma, Jinfeng Ge, Qiaozhuan Hu, Fu-Jun Yue, Si-Liang Li and Dietrich A. Volmer
Molecules 2021, 26(1), 178; https://doi.org/10.3390/molecules26010178 - 01 Jan 2021
Cited by 17 | Viewed by 4411
Abstract
Lignin is the second most abundant natural biopolymer, which is a potential alternative to conventional fossil fuels. It is also a promising material for the recovery of valuable chemicals such as aromatic compounds as well as an important biomarker for terrestrial organic matter. [...] Read more.
Lignin is the second most abundant natural biopolymer, which is a potential alternative to conventional fossil fuels. It is also a promising material for the recovery of valuable chemicals such as aromatic compounds as well as an important biomarker for terrestrial organic matter. Lignin is currently produced in large quantities as a by-product of chemical pulping and cellulosic ethanol processes. Consequently, analytical methods are required to assess the content of valuable chemicals contained in these complex lignin wastes. This review is devoted to the application of mass spectrometry, including data analysis strategies, for the elemental and structural elucidation of lignin products. We describe and critically evaluate how these methods have contributed to progress and trends in the utilization of lignin in chemical synthesis, materials, energy, and geochemistry. Full article
(This article belongs to the Special Issue Lignin for Energy, Chemicals and Materials II)
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