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Special Issue "Lignin for Energy, Chemicals and Materials"

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

Deadline for manuscript submissions: 30 June 2018

Special Issue Editors

Guest Editor
Prof. Dr. Charles Xu

Institute for Chemicals and Fuels from Alternative Resources (ICFAR), Department of Chemical and Biochemical Engineering, Western University, Ontario, Canada
Website | E-Mail
Phone: 519-661-2111 ext. 86414
Fax: 519-661-4016
Interests: Biorefining technologies; Bio-fuels; Bio-based chemicals; Bio-based materials; Thermochemical conversion; Hydrothermal liquefaction; Pyrolysis; Combustion; Gasification; Lignocellulosic biomass; Forestry residues; Agricultural residues; Sugars; Starch; Cellulose; Lignin; Municipal solid wastes; Wastewater sludge; Catalysis; Catalysts; Chemical reaction engineering; Green process engineering
Guest Editor
Dr. Michael Paleologou

Research Leader, Lignin Products, Biorefinery Program, FPInnovations, 570 boul. Saint-Jean, Pointe-Claire(QC) H9R 3J9, Canada
E-Mail
Interests: forest biorefinery; lignin recovery; lignin characterization; lignin products; hemicellulose recovery; hemicellulose products; methanol recovery; biomass processing operations; process integration and economics; black and red liquor characterization; chemical recovery; chemical separation and regeneration technologies for kraft, sulphite and BCTMP mills; system closure

Special Issue Information

Dear Colleagues,

Lignin is the second most abundant natural renewable polymer after cellulose. Natural lignin is a phenolic polymer of three monolignols with an amorphous macromolecular structure. Lignin is currently being produced in large quantities as a by-product of chemical pulping and cellulosic ethanol processes. According to the International Lignin Institute, about 40–50 million tonnes 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 the 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 by-products 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 bio-fuels, or gasification of lignin for syngas/hydrogen, etc.). The presence of various functional groups (aromatic ring free positions and hydroxyl groups) on lignin structure, biodegradability, antioxidant, flame retardant and reinforcing capability make it as 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, light-weight composite materials, as well as graphene for use in supercapacitors for energy storage. Direct use of lignin for chemical synthesis and materials can be challenging because the molecular weight is too high and because reactivity is reduced due to steric hindrance effects. The reactivity of lignin could be enhanced through some chemical modifications and thermochemical de-polymerization processes.

This Special Issue aims to cover recent progress and trends in the utilization of lignin or modified/de-polymerized lignin in chemical synthesis, materials and energy. Submissions are welcome but not limited to the topics listed below. Types of contributions to this Special Isssue 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/de-polymerization of lignin;
  • Combustion/co-combustion of lignin for energy;
  • Pyrolysis or hydrothermal liquefaction of lignin for bio-oils/liquid bio-fuels;
  • 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 light-weight composite materials
  • Production of graphene for use in supercapacitors for energy storage.

Prof. Chunbao (Charles) Xu
Dr. Michael Paleologou
Guest Editors

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 papers will be 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 monthly 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 1800 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
  • De-polymerization
  • Combustion
  • Energy
  • Pyrolysis
  • Hydrothermal liquefaction
  • Bio-oils
  • Phenols
  • Bio-aromatic chemicals
  • Synthesis
  • Resins
  • Polymers
  • Carbon fibers
  • Composites
  • Graphene
  • Supercapacitors

Published Papers (6 papers)

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Research

Jump to: Review

Open AccessArticle Production of Micro- and Nanoscale Lignin from Wheat Straw Using Different Precipitation Setups
Molecules 2018, 23(3), 633; doi:10.3390/molecules23030633
Received: 30 January 2018 / Revised: 7 March 2018 / Accepted: 9 March 2018 / Published: 11 March 2018
PDF Full-text (5203 KB) | HTML Full-text | XML Full-text
Abstract
Micro- and nanosize lignin has recently gained interest due to its improved properties compared to standard lignin available today. As the second most abundant biopolymer after cellulose, lignin is readily available but used for rather low-value applications. Applications for lignin in micro- to
[...] Read more.
Micro- and nanosize lignin has recently gained interest due to its improved properties compared to standard lignin available today. As the second most abundant biopolymer after cellulose, lignin is readily available but used for rather low-value applications. Applications for lignin in micro- to nanoscale however, ranging from improvement of mechanical properties of polymer nanocomposites, have bactericidal and antioxidant properties and impregnations to hollow lignin drug carriers for hydrophobic and hydrophilic substances. This research represents a whole biorefinery process chain and compares different precipitation setups to produce submicron lignin particles from lignin containing an organosolv pretreatment extract from wheat straw. A batch precipitation in a stirred vessel was compared with continuous mixing of extract and antisolvent in a T-fitting and mixing in a T-fitting followed by a static mixer. The precipitation in the combination of T-fitting and static mixer with improved precipitation parameters yields the smallest particle size of around 100 nm. Furthermore, drying of particles did not influence the particle sizes negatively by showing decreased particle diameters after the separation process. Full article
(This article belongs to the Special Issue Lignin for Energy, Chemicals and Materials)
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Open AccessArticle Lignin from Hardwood and Softwood Biomass as a Lubricating Additive to Ethylene Glycol
Molecules 2018, 23(3), 537; doi:10.3390/molecules23030537
Received: 30 January 2018 / Revised: 22 February 2018 / Accepted: 23 February 2018 / Published: 28 February 2018
PDF Full-text (3548 KB) | HTML Full-text | XML Full-text
Abstract
Ethylene glycol (EG)-based lubricant was prepared with dissolved organosolv lignin from birch wood (BL) and softwood (SL) biomass. The effects of different lignin types on the rheological, thermal, and tribological properties of the lignin/EG lubricants were comprehensively investigated by various characterization techniques. Dissolving
[...] Read more.
Ethylene glycol (EG)-based lubricant was prepared with dissolved organosolv lignin from birch wood (BL) and softwood (SL) biomass. The effects of different lignin types on the rheological, thermal, and tribological properties of the lignin/EG lubricants were comprehensively investigated by various characterization techniques. Dissolving organosolv lignin in EG results in outstanding lubricating properties. Specifically, the wear volume of the disc by EG-44BL is only 8.9% of that lubricated by pure EG. The enhanced anti-wear property of the EG/lignin system could be attributed to the formation of a robust lubrication film and the strong adhesion of the lubricant on the contacting metal surface due to the presence of a dense hydrogen bonding (H-bonding) network. The lubricating performance of EG-BL outperforms EG-SL, which could be attributed to the denser H-bonding sites in BL and its broader molecular weight distribution. The disc wear loss of EG-44BL is only 45.7% of that lubricated by EG-44SL. Overall, H-bonding is the major contributor to the different tribological properties of BL and SL in EG-based lubricants. Full article
(This article belongs to the Special Issue Lignin for Energy, Chemicals and Materials)
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Open AccessFeature PaperArticle Quantification and Variability Analysis of Lignin Optical Properties for Colour-Dependent Industrial Applications
Molecules 2018, 23(2), 377; doi:10.3390/molecules23020377
Received: 11 January 2018 / Revised: 4 February 2018 / Accepted: 6 February 2018 / Published: 10 February 2018
PDF Full-text (4349 KB) | HTML Full-text | XML Full-text
Abstract
Lignin availability has increased significantly due to the commercialization of several processes for recovery and further development of alternatives for integration into Kraft pulp mills. Also, progress in lignin characterization, understanding of its chemistry as well as processing methods have resulted in the
[...] Read more.
Lignin availability has increased significantly due to the commercialization of several processes for recovery and further development of alternatives for integration into Kraft pulp mills. Also, progress in lignin characterization, understanding of its chemistry as well as processing methods have resulted in the identification of novel lignin-based products and potential derivatives, which can serve as building block chemicals. However, all these have not led to the successful commercialization of lignin-based chemicals and materials. This is because most analyses and characterizations focus only on the technical suitability and quantify only the composition, functional groups present, size and morphology. Optical properties, such as the colour, which influences the uptake by users for diverse applications, are neither taken into consideration nor analysed. This paper investigates the quantification of lignin optical properties and how they can be influenced by process operating conditions. Lignin extraction conditions were also successfully correlated to the powder colour. About 120 lignin samples were collected and the variability of their colours quantified with the CIE L*a*b* colour space. In addition, a robust and reproducible colour measurement method was developed. This work lays the foundation for identifying chromophore molecules in lignin, as a step towards correlating the colour to the functional groups and the purity. Full article
(This article belongs to the Special Issue Lignin for Energy, Chemicals and Materials)
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Open AccessArticle Sustainable Bio-Based Phenol-Formaldehyde Resoles Using Hydrolytically Depolymerized Kraft Lignin
Molecules 2017, 22(11), 1850; doi:10.3390/molecules22111850
Received: 11 September 2017 / Revised: 26 October 2017 / Accepted: 27 October 2017 / Published: 28 October 2017
Cited by 1 | PDF Full-text (11454 KB) | HTML Full-text | XML Full-text
Abstract
In this study bio-based bio-phenol-formaldehyde (BPF) resoles were prepared using hydrolytically depolymerized Kraft lignin (DKL) as bio-phenol to partially substitute phenol. The effects of phenol substitution ratio, weight-average molecular weight (Mw) of DKL and formaldehyde-to-phenol (F/P) ratio were also investigated
[...] Read more.
In this study bio-based bio-phenol-formaldehyde (BPF) resoles were prepared using hydrolytically depolymerized Kraft lignin (DKL) as bio-phenol to partially substitute phenol. The effects of phenol substitution ratio, weight-average molecular weight (Mw) of DKL and formaldehyde-to-phenol (F/P) ratio were also investigated to find the optimum curing temperature for BPF resoles. The results indicated that DKL with Mw ~ 1200 g/mol provides a curing temperature of less than 180 °C for any substitution level, provided that F/P ratios are controlled. Incorporation of lignin reduced the curing temperature of the resin, however, higher Mw DKL negatively affected the curing process. For any level of lignin Mw, the curing temperature was found to increase with lower F/P ratios at lower phenol substitution levels. At 25% and 50% phenol substitution, increasing the F/P ratio allows for synthesis of resoles with lower curing temperatures. Increasing the phenol substitution from 50% to 75% allows for a broader range of lignin Mw to attain low curing temperatures. Full article
(This article belongs to the Special Issue Lignin for Energy, Chemicals and Materials)
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Open AccessArticle Valorization of Lignin by Partial Wet Oxidation Using Sustainable Heteropoly Acid Catalysts
Molecules 2017, 22(10), 1625; doi:10.3390/molecules22101625
Received: 12 September 2017 / Revised: 25 September 2017 / Accepted: 27 September 2017 / Published: 28 September 2017
Cited by 2 | PDF Full-text (2138 KB) | HTML Full-text | XML Full-text
Abstract
The production of carboxylic acids by partial wet oxidation of alkali lignin at elevated temperatures and pressures was studied experimentally. Two different heteropoly acids, phosphotungstic acid (H3PW12O40) and phosphomolybdic acid (H3PMo12O40),
[...] Read more.
The production of carboxylic acids by partial wet oxidation of alkali lignin at elevated temperatures and pressures was studied experimentally. Two different heteropoly acids, phosphotungstic acid (H3PW12O40) and phosphomolybdic acid (H3PMo12O40), were used to catalyze the oxidation of lignin under hydrothermal conditions. Factors influencing the total yield of carboxylic acids formed during the partial oxidation of lignin were investigated. Formic, acetic and succinic acids were the major products identified. Of the two catalysts used, phosphomolybdic acid gave the most promising results, with carboxylic acid yields and lignin conversions of up to 45% and 95%, respectively. Full article
(This article belongs to the Special Issue Lignin for Energy, Chemicals and Materials)
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Review

Jump to: Research

Open AccessReview Production of Flocculants, Adsorbents, and Dispersants from Lignin
Molecules 2018, 23(4), 868; doi:10.3390/molecules23040868
Received: 11 March 2018 / Revised: 3 April 2018 / Accepted: 6 April 2018 / Published: 10 April 2018
PDF Full-text (5701 KB) | HTML Full-text | XML Full-text
Abstract
Currently, lignin is mainly produced in pulping processes, but it is considered as an under-utilized chemical since it is being mainly used as a fuel source. Lignin contains many hydroxyl groups that can participate in chemical reactions to produce value-added products. Flocculants, adsorbents,
[...] Read more.
Currently, lignin is mainly produced in pulping processes, but it is considered as an under-utilized chemical since it is being mainly used as a fuel source. Lignin contains many hydroxyl groups that can participate in chemical reactions to produce value-added products. Flocculants, adsorbents, and dispersants have a wide range of applications in industry, but they are mainly oil-based chemicals and expensive. This paper reviews the pathways to produce water soluble lignin-based flocculants, adsorbents, and dispersants. It provides information on the recent progress in the possible use of these lignin-based flocculants, adsorbents, and dispersants. It also critically discusses the advantages and disadvantages of various approaches to produce such products. The challenges present in the production of lignin-based flocculants, adsorbents, and dispersants and possible scenarios to overcome these challenges for commercial use of these products in industry are discussed. Full article
(This article belongs to the Special Issue Lignin for Energy, Chemicals and Materials)
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Figure 1a

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Author: Abayneh Demesa
Affiliation: Laboratory of Process and Product Development, LUT School of Engineering Science, Lappeenranta University of Technology, Skinnarilankatu 34, FI-53850 Lappeenranta, Finland
Tentative title: Lignin valorization for chemical production

Author: Rehman Javaid, Aqsa Sabir, Nadeem Sheikh, Muhammad Ferhan
Affiliation:  Lignin Valorization & Nanomaterials Lab, Centre for Applied Molecular Biology (CAMB),
University of the Punjab, 87-West Canal Bank Road, Thokar Niaz Baig, Lahore-53700, Pakistan
Institute of Molecular Biology and Biotechnology (IMBB), The University of Lahore, 1- KM Raiwind Road, Lahore
Tentative title: Recent advances in applications of acidophilic fungal microbes for bio-chemicals.
Tentative abstract: Lignocellulosic feedstock (cellulose, hemicellulose and lignin) has been used for a variety of purposes. Among them, lignin can produce value-added chemicals containing a variety of structurally related phenyl propanoid subunits known as core lignin, consisting of either C-C bonds or ether linkages. It can be depolymerized by microbial activity together with certain enzymes (laccases and peroxidases). Both acetic acid and formic acid production by certain fungi contribute significantly to lignin depolymerization to obtain most chemicals substances. Natural organic acids production by fungi has many key roles in nature that are strictly dependent upon organic acid producing fungus type. Enzymatic conversion of lignocellulosic is beneficial over other physio-chemical processes because of enzymatic specificity in reactions. Laccases, the copper containing proteins contribute to oxidize a broad spectrum of inorganic as well as organic compounds but most specifically phenolic compounds by radical catalyzed mechanism. Similarly, lignin peroxidases (LiP), the heme containing proteins perform a vital part in oxidizing a wide variety of aromatic compounds with H2O2. Lignin depolymerization yields polyaromatics, the important of which are BTX (Benzene, Toluene and Xylene). These aromatic complexes are found in several different configurations. However, most modern aromatics complexes enhance the production of para-xylene, benzene and sometimes ortho-xylene respectively. Thus, the aim of this review is to provide a concept that chemical and biological modifications of lignin yield certain value added and environment friendly green biochemicals.

Author: Basma El Khaldi-Hansen, Abla Alzazgameem, Birgit Kamm and Margit Schulze1,*
Tentative title: Lignin-Derived Biomaterials for Drug Release and Tissue Engineering
Tentative abstract: Renewable resources gain increasing interest as source for environmentally benign biomaterials, such as drug encapsulation and release compounds, and scaffolds for tissue engineering in regenerative medicine. Being the second largest naturally abundant polymer, the interest in lignin utilization in biomedicine is rapidly growing. Within the last five years, remarkable progress has been made in isolation, functionalization and modification of lignin and lignin-derived materials. However, literature so far (including review articles) most often focus industrial utilization such as fuels, resins and lubricants. The purpose of this review is to summarize the current state of the art and highlight the most important results of lignin-derived materials for biomedicine (cited references include original paper and patents in 2013-18). Special focus is drawn on guided bone regeneration: 3D scaffolds are known to directly influence differentiation and proliferation of mesenchymal stem cells into bone tissue due to scaffold structure (polarity, porosity, surface topography) and controlled release of osteoinductive and/or osteoconductive drugs. The review highlights recent progresses in guided bone formation, including stem cell-based approaches for future therapies.
Keywords: biomaterial, bone regeneration, drug encapsulation, drug release, lignin, osteogenesis, scaffolds, stem cells, tissue engineering.

Author: Thomas Rosenau
Affiliation: Universitat fur Bodenkultur Wien, Vienna, Austria
Tentative title: Lignin-based foams for insulation - a review
Tentative abstract: The bulk use of renewable polymers is largely limited to cellulose and, less significantly, hemicelluloses. The situation is quite different for lignin which finds application in novel materials only to a very small extent. Lignin, which is the second most abundant biopolymer, is currently only used in low-performance applications or is simply burned for energy ("energetic utilization"). Due to its attractive chemical structure, i.e. different reactive chemical motifs, together with the huge quantities available from pulping processes, technical lignins have indeed potential for innovative applications on larger scale, which hopefully will find access to the markets in the near future. Promising applications for lignin are thermal insulation materials, 3D printing, membranes in separation processes, packaging and adsorbent materials, fertilizers, to name but a few. In this review, the state of the art of foamed lignin-based polymers, so called lignofoams, as high performance insulation materials, is presented. Fundamental foaming principles and influential agents which directly or potentially improve the matrix interactions between lignin/lignosulfonate and a copolymer for foam composites are discussed, and different approaches are critically compared.

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