A low-cost and green biorefinery will increase the economy and revenue from lignocellulosic biomass. Herein, a biomass-derived deep eutectic solvent (DES) pretreatment was developed to deconstruct ...the recalcitrant structure of Eucalyptus for further cellulose enzymatic hydrolysis and lignin valorization. The DES consisted of biomass-derived chemicals (lactic acid and choline chloride). The results showed that DES pretreatment resulted in notable removal of hemicelluloses and lignin, and drastically reduced “biomass recalcitrance”. Under the optimum conditions (DES ratio: 10 : 1, temperature: 110 °C, time: 6 h), the glucose yield by enzymatic hydrolysis reached 94.3%, which was significantly enhanced 9.8 times compared to that of the original biomass without DES pretreatment. The state-of-the-art analysis indicated that the regenerated lignin exhibited well-preserved structures ( i.e. , β- O -4, β–β linkages) without contaminated carbohydrates, and it had a relatively low and homogeneous molecular weight. All these structural characteristics suggested that lignin has great potential application in its conversion into bio-based chemicals and materials. Besides, it is urgent to develop low-cost recycled DESs as green solvents for sustainable biomass pretreatment. The lifetime and recyclability experiment of the DES solution showed that the recovery yield of the DES was at least 90% and the fundamental structural properties of the recycled DES were almost unchanged throughout the recycling cycles. More importantly, the pretreatment efficiency (delignification and enzymatic saccharification) was still largely maintained after the recycling process. Overall, this work demonstrated that biomass pretreatment with the recycled DES was promising for a low-cost biorefinery to achieve an efficient fractionation of lignocellulosic biomass into fermentable glucose and high-quality lignin with tailored chemical structures.
The lignin‐first strategy has emerged as one of the most powerful approaches for generating novel platform chemicals from lignin by efficient depolymerization of native lignin. Because of the ...emergence of this novel depolymerization method and the definition of viable platform chemicals, future focus will soon shift towards innovative downstream processing strategies. Very recently, many interesting approaches have emerged that describe the production of valuable products across the whole value chain, including bulk and fine chemical building blocks, and several concrete examples have been developed for the production of polymers, pharmaceutically relevant compounds, or fuels. This Minireview provides an overview of these recent advances. After a short summary of catalytic systems for obtaining aromatic monomers, a comprehensive discussion on their separation and applications is given. This Minireview will fill the gap in biorefinery between deriving high yields of lignin monomers and tapping into their potential for making valuable consumer products.
Worry about it later: The lignin‐first strategy is a powerful approach for generating platform chemicals by efficient depolymerization of lignin. Recent progress has been made in developing innovative downstream processing strategies to afford bulk and fine chemical building blocks, polymers, pharmaceutically relevant compounds, and fuels. This Minireview provides an overview of these recent advances.
Lithium–sulfur (Li–S) batteries are highly regarded as the next‐generation energy‐storage devices because of their ultrahigh theoretical energy density of 2600 Wh kg−1. Sulfurized polyacrylonitrile ...(SPAN) is considered a promising sulfur cathode to substitute carbon/sulfur (C/S) composites to afford higher Coulombic efficiency, improved cycling stability, and potential high‐energy‐density Li–SPAN batteries. However, the instability of the Li‐metal anode threatens the performances of Li–SPAN batteries bringing limited lifespan and safety hazards. Li‐metal can react with most kinds of electrolyte to generate a protective solid electrolyte interphase (SEI), electrolyte regulation is a widely accepted strategy to protect Li‐metal anodes in rechargeable batteries. Herein, the basic principles and current challenges of Li–SPAN batteries are addressed. Recent advances on electrolyte regulation towards stable Li‐metal anodes in Li–SPAN batteries are summarized to suggest design strategies of solvents, lithium salts, additives, and gel electrolyte. Finally, prospects for future electrolyte design and Li anode protection in Li–SPAN batteries are discussed.
Increased attention SPAN: Recent advances in electrolyte regulation towards stable lithium‐metal anodes for Li‐sulfurized polyacrylonitrile (SPAN) batteries are summarized to afford design strategies of solvents, lithium salts, additives, and gel electrolyte.
Lignin is the most abundant natural aromatic feedstock, and the conversion of lignin to value-added chemicals has drawn immense attention in biorefineries. Deep eutectic solvents (DESs) have been ...used for lignocellulosic biomass fractionation and lignin extraction due to their simple procedure, selective solubility of lignin, low cost, and high recyclability. The nature and number of functional groups in DESs remarkably influence the delignification and structural changes of lignin during treatment. Although many studies have investigated lignin extraction and the following chemical transformations during DES treatment, no review has illuminated the structure-function relationships between DESs and lignin. This review presents a systematic overview of important studies to provide insights into lignin extraction and chemical transformations by examining the relationship between the type and number of functional groups in DES constituents during pretreatment. Furthermore, various challenges and opportunities in the development of more sustainable and efficient lignin extraction are provided according to the remaining problems in this field.
The effect of the structure and properties of DESs on lignin extraction and chemical transformations.
The excessive use of petroleum-based non-biodegradable plastic products has resulted in severe environmental pollution and ecological problems, which has stimulated the development of biodegradable ...and renewable alternative materials. Lignin, as the most abundant aromatic polymer with great biodegradability and biocompatibility, exhibits enormous potential for preparing various functional and sustainable materials as alternatives to plastics. Recently, lignin-derived biodegradable films have received extensive attention in both fundamental research and practical applications, and many significant achievements have been made in this field. Herein, the latest progress in the preparation and advanced applications of lignin-derived biodegradable film materials is summarized from a sustainability point of view. An introduction to the structural and chemical characteristics of lignin is presented first, and then the designs and advances of construction systems are reviewed based on the building matrixes, including lignocellulose, natural macromolecules, biodegradable synthetic copolymers, and other cutting-edge materials. In this review, the tailored applications of these film materials are mainly focused on sensors and responsive materials, energy storage systems, packaging, and biomedical materials. Finally, the main challenges of lignin-derived biodegradable film materials are presented, and potential development directions for sustainable and eco-friendly lignin-derived film materials are also proposed.
This review summarizes the recent advances in fabrication strategies and versatile applications of lignin-derived biodegradable film materials from the viewpoint of sustainable development.
Lignin is expected to replace traditional fossil energy and convert it into a carbon material with excellent performance because of its advantages of being green and renewable, and its abundant ...reserves that are cheap and easy to obtain. The substitution of lignin for petroleum-based materials can not only effectively realize the high-value utilization of biomass, but reduce environmental pollution and energy loss. This work reported a simple and relatively low-temperature method to produce lignin-based graphene-like carbon materials. In this study, a lignin-based graphene-like film with micron thickness was successfully prepared by carbonization at a relatively low temperature (800 °C) using alkali lignin (AL) as a solid carbon source and large-area metal Ni sheets as catalyst. Through a series of characterization studies of the obtained products at different temperatures, the structural changes of AL and the growth process of the crystal nucleus are further explained. Moreover, the lattice fringes in few-layer graphene were observed by high resolution transmission electron microscopy, which showed that graphitic carbon structures are formed under the catalysis of metal Ni sheets. To sum up, the process was simple and low in energy consumption, and successfully converted biomass resource AL into high value-added carbon material products, alleviating the current problems of energy consumption and climate pollution.
To meet the huge market demand for carbon fibers (CFs), great efforts have been focused on developing low-cost and sustainable CFs with comparable properties. Lignin, a polyaromatic heteropolymer in ...nature, is considered a promising precursor suitable for CFs fabrication due to its abundant, renewable, low-cost, high-carbon, thermostable, and thermoplastic characteristics. Although research on lignin-based carbon fibers (LCFs) has achieved impressive results, their mechanical properties are still inferior to those of commercialized CFs. In this review, the structural characteristics of the lignin polymers from different plant sources and isolation methods are introduced. The key factors affecting LCFs performances and the effective strategies aiming to improve the properties of LCFs are also summarized in detail, revealing the influences of structural features of lignin on the performances of LCFs. In particular, recent advances in precursors, spinning techniques, stabilization, carbonization, graphitization, and activization of LCFs since 2017 are systematically reviewed. Furthermore, to expand the new applications of LCFs, a comprehensive overview of LCFs applications in diverse fields (electrochemical energy storage, adsorption, catalysis, and other emerging fields) is provided. Finally, the current challenges and opportunities for the future development of LCFs are proposed.
The precursor formulations, fabrications, properties, and various applications of lignin-based carbon fibers (LCFs) since 2017 are reviewed.
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•The basic principles and developments of hydrothermal pretreatment are reviewed.•The ultrastructural alterations during hydrothermal pretreatment are discussed.•The effects of ...hydrothermal pretreatment on bioethanol production are addressed.•The prospects for future developments are proposed and discussed.
In recent years, visualization and characterization of lignocellulose at different scales elucidate the modifications of its ultrastructural and chemical features during hydrothermal pretreatment which include degradation and dissolving of hemicelluloses, swelling and partial hydrolysis of cellulose, melting and redepositing a part of lignin in the surface. As a result, cell walls are swollen, deformed and de-laminated from the adjacent layer, lead to a range of revealed droplets that appear on and within cell walls. Moreover, the certain extent morphological changes significantly promote the downstream processing steps, especially for enzymatic hydrolysis and anaerobic fermentation to bioethanol by increasing the contact area with enzymes. However, the formation of pseudo-lignin hinders the accessibility of cellulase to cellulose, which decreases the efficiency of enzymatic hydrolysis. This review is intended to bridge the gap between the microstructure studies and value-added applications of lignocellulose while inspiring more research prospects to enhance the hydrothermal pretreatment process.
Deep eutectic solvents (DESs) as novel and green solvents can extract high-purity lignin from lignocellulose in a high yield; however, further utilization of the extracted lignin in the DES is a ...severe challenge in biorefinery processes. Nevertheless, the potential of lignin valorization can be precisely reflected by unveiling the chemical transformations of lignin during DES pretreatment. In this study, we aimed to understand the possible transformation pathway
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thorough characterization of the regenerated lignin and lignin oil and transformation of lignin into value-added products. During this process, alkali lignin (AL) isolated from poplar was pretreated with choline chloride-lactic acid (ChCl-LA) and choline chloride-oxalic acid (ChCl-OA) at 80-120 °C for 6 hours to produce the regenerated lignin and lignin oil. The yield of the regenerated lignin ranged from 44 to 75% after DES pretreatment. During ChCl-LA pretreatment, γ-acetylated groups in the regenerated lignin were observed at low temperatures and then deacylation occurred at high temperatures, which was beneficial for oxidizing lignin and producing phenolic diketones. Additionally, the depolymerization of lignin fractions was the dominant reaction during DES pretreatment, accompanied by partial condensation reactions. More importantly, this is the first report of obtaining S- and G-derived diketones from lignin oil after DES pretreatment. The degradation mechanism of lignin in the DES system has been proposed. This work opens a way to produce value-added chemicals from lignin in DESs, which needs to be researched in the future.
The chemical transformations of lignin in an acidic DES system.
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