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Lignocellulosic biomass, especially lignin and extractives, has the potential to substitute fossil precursors in the chemical industry. The conversion of lignin has been intensively researched, but challenges remain as high temperatures and increased pressure are commonly used, which is not energy efficient. Lignin and wood extractives bear chromophoric groups that can absorb light in the ultraviolet (UV) region, which enables photochemical reactions. Ultraviolet light emitting diodes (UV-LEDs) are an emerging technology; they are cheap, versatile, and energy-efficient compared to existing mercury lamps. UV-LEDs were used in this study as a proof of concept for the valorisation of a lignocellulosic residual stream from the pulp and paper industry, sawdust. In a process at ambient temperature and pressure and without the use of a catalyst, we have shown that lignin and extractives can be valorised using light from UV-LEDs. Simplified lignin model compounds were used to pinpoint chemical reactions during irradiation, and to ease the analysis of the sawdust samples. The rate of conversion upon irradiation of the model compounds was found to be 0.7–2.3 g L−1 h−1, depending on the concentration of the starting compounds. [ABSTRACT FROM AUTHOR]

The pulp and paper industry together with lignocellulosic biofuel production provides plentiful streams of lignin and lignin-derived molecules (LDMs) that currently remain underutilized. The heterogeneity and complexity of lignin along with the lack of convenient tools significantly hamper its utilization. Selective separation of these LDMs from streams using specific tools would allow the recovery of aromatic compounds, as well as facilitate biological processes aiming at lignin valorization. To this end, here we report the isolation and characterization of single-chain variable fragment (scFv) antibodies against ferulate, coumarate, and caffeate, which are the molecular representatives of LDMs. Binders for the target LDMs were enriched by interrogating a synthetic scFv library with the phage display technique. As a result, scFv binders specific against each of the target molecules were obtained with affinities in the micromolar range. The selectivity of scFvs towards specific LDMs was proved by recovering caffeate from simulated LDM solution, Kraft lignin, and rice straw hydrolysate samples. Further proof of concept studies with model compounds demonstrated the applicability of antibody-based binders as a detection tool for monitoring microbial LDM conversion. Overall, this study demonstrates the potential of scFv binders as a specific toolset for lignin compound recovery and analysis. [ABSTRACT FROM AUTHOR]

This document is a contents list for the journal "Green Chemistry," published by the Royal Society of Chemistry. It features research papers on various topics related to sustainable chemistry, including photocatalytic upgrading of hydroxymethylfurfural, lignin extraction and nanodispersion, selenium-doped carbon materials, and the valorization of bio-renewable glycerol. The journal also includes tutorial reviews on topics such as Pickering emulsion-derived nano/microreactors and the iron ligand-to-metal charge transfer chemistry in water. Additionally, there are perspective papers, communications, and other research papers covering a range of subjects in green chemistry. The papers provide valuable insights into the development of greener and more sustainable chemical processes. [Extracted from the article]

Both softwood (southern yellow pine) and hardwood (red oak) can be completely dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate ([C2mim]OAc) after mild grinding. Complete dissolution was achieved by heating the sample in an oil bath, although wood dissolution can be accelerated by microwave pulses or ultrasound irradiation. It has been shown that [C2mim]OAc is a better solvent for wood than 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) and that variables such as type of wood, initial wood load, particle size, etc.affect dissolution and dissolution rates; for example, red oak dissolves better and faster than southern yellow pine. Carbohydrate-free lignin and cellulose-rich materials can be obtained by using the proper reconstitution solvents (e.g., acetone/water 1 : 1 v/v) and approximately 26.1% and 34.9% reductions of lignin content in the reconstituted cellulose-rich materials (from pine and oak, respectively) have been achieved in one dissolution/reconstitution cycle. The regenerated cellulose-rich materials and lignin fractions were characterized and compared with the original wood samples and biopolymer standards. For pine, 59% of the holocellulose (i.e., the sum of cellulose and hemicellulose) in the original wood can be recovered in the cellulose-rich reconstituted material; whereas 31% and 38% of the original lignin is recovered, respectively, as carbohydrate-free lignin and as carbohydrate-bonded lignin in the cellulose-rich material. [ABSTRACT FROM AUTHOR]

A lack of renewable resources and their inefficient use is a major challenge facing the society. Lignin is a natural biopolymer obtained mainly as a by-product from the pulp- and paper-making industries, and is primarily burned to produce energy. However, interest for using lignin in more advanced applications has increased rapidly. In particular, lignin based nanoparticles could find potential use in functional surface coatings, nanoglue, drug delivery, and microfluidic devices. In this work, a straightforward method to produce lignin nanoparticles from waste lignin obtained from kraft pulping is introduced. Spherical lignin nanoparticles were obtained by dissolving softwood kraft lignin in tetrahydrofuran (THF) and subsequently introducing water into the system through dialysis. No chemical modification of lignin was needed. Water acts as a non-solvent reducing lignin's degrees of freedom causing the segregation of hydrophobic regions to compartments within the forming nanoparticles. The final size of the nanoparticles depended on the pre-dialysis concentration of dissolved lignin. The stability of the nanoparticle dispersion as a function of time, salt concentration and pH was studied. In pure water and at room temperature the lignin nanoparticle dispersion was stable for over two months, but a very low pH or high salt concentration induced aggregation. It was further demonstrated that the surface charge of the particles could be reversed and stable cationic lignin nanoparticles were produced by adsorption of poly(diallyldimethylammonium chloride) (PDADMAC). [ABSTRACT FROM AUTHOR]

This study shows a functional deep eutectic solvent (DES) employing choline chloride (ChCl) and glyoxylic acid (GA) for lignocellulose fractionation. This DES exhibited a higher pretreatment efficiency (92.15%) than that composed of ChCl and lactic acid (10.36%). Molecular dynamic (MD) simulations indicated that the ChCl : GA DES showed a higher total binding energy (ΔE) with lignin than the ChCl : LA DES, resulting in a higher dissolution of lignin. GA prevented lignin condensation during pretreatment. The stabilized lignin containing 69.39% β-O-4 linkages can be used for phenolic monomer production with a bio-oil yield of 59.60% and lignin-based sunscreen preparation with a SPF of 58.46. The cellulose residues with a mild pretreatment severity exhibited a high enzymatic saccharification yield of 91.99%. Meanwhile, an esterification reaction occurred between cellulose and GA during pretreatment. The inhibition of enzymatic hydrolysis and microbial growth enables the use of functional cellulose to produce antibacterial paper. Furthermore, 96.80% of the DES could be easily recycled and reused for biorefinery purposes. [ABSTRACT FROM AUTHOR]

The electrochemical reductive cleavage of the C–O bond in the lignin α-O-4 model compound benzyl phenyl ether (BPE) at room temperature was investigated using earth-abundant nickel as a catalyst in methanol. Experiments using a divided cell setup using either NiCl2·6H2O salt or pre-deposited Ni on a carbon paper cathode (Ni/CP) under an inert atmosphere revealed the essential role of freshly and uniformly deposited Ni0 on the electrode surface for the reductive, catalytic cleavage to yield phenol and toluene. To better understand the reaction mechanism, the surface morphology and composition of the Ni/CP electrode were investigated by SEM, XRD, and XPS. Additionally, the role of methanol as a proton donor was established, and electrochemical hydrogenation/hydrogenolysis (ECH) experiments of BPE with sterically hindered substituents revealed that the reaction mechanism shares similarities with Pd/C hydrogenation/hydrogenolysis chemistry. DFT calculations further supported this mechanistic route and were consistent with the experimental observations. Based on both experimental and calculation results, a mechanism including (1) the interaction of the benzylic side of BPE with the catalyst surface, (2) adsorbed hydrogen interacting with the benzylic carbon to induce C–O bond scission, and (3) proton transfer to the phenoxy anion from the methanol was proposed. [ABSTRACT FROM AUTHOR]

Current catalytic hydrogenolysis of lignin C–O bonds, which is crucial for lignin valorization, often requires a noble metal catalyst or/and harsh conditions such as elevated temperatures and high pressures. Herein, we report a highly selective electrochemical protocol to reductively cleave the benzylic C–O bond of the α-O-4 lignin model compound benzyl phenyl ether (BPE) at room temperature and ambient pressure. Nearly complete conversion of BPE to toluene and phenol in methanol was achieved in an undivided cell using Ni foam at both the anode and cathode, with yields of 97% and 30%, respectively. Using a divided cell, yields of 90% (toluene) and 84% (phenol) could be achieved using inexpensive carbon paper as the cathode when Ni(II) salts were added to the cathode chamber. Notably, other divalent metal salts did not lead to any product formation, suggesting a unique role of Ni ions in benzylic C–O bond cleavage. Further, a substrate scope study revealed the suitability of the method for a variety of substituted BPEs. This work provides an economical and environmentally friendly method for selective cleavage of C–O bonds in benzylic ethers as model compounds for lignin. [ABSTRACT FROM AUTHOR]

Eucalyptus dissolving kraft pulp pre-hydrolysis liquor (PHL) is rich in sugar and other biomass resources, which can produce furfural and may serve as a platform molecule for sustainable fuel production. However, the presence of lignin increases the side reactions during the high-value utilization of PHL. Therefore, a novel process technology, consisting of laccase-induced lignin polymerization, was developed in this paper to enhance the removal of lignin. During the study, the mechanism of the action of laccase on lignin was speculated and it was discovered that the effect of laccase on lignin is to polymerize its small molecules. The main reaction of laccase oxidation is the formation of 5-5′ and 4-O-5′ bonds, and occasionally β-O-4′. If position 5 is blocked, other side reactions will occur, including coupling at position 1 and oxidation at position α. Simultaneously, the –OH content of lignin increases under the activation of laccase. Then, the conversion of furfural from the delignified pre-hydrolysis liquor (LPHL) under the catalysis of 2 wt% sulfuric acid was investigated. With the traditional one-pot reactor system, furfural and the reaction medium cannot be separated in time and the degradation of furfural cannot be prevented. The side reactions caused by this, such as fragmentation, condensation and resinification, which is visible to the naked eye, involve the production of humic substances, which becomes the most important factor in the low furfural yield. These side reactions are verified by GC/MS. According to the results in this study, the biorefinery process towards PHL, which allows the separation of lignin by laccase and the conversion of xylose to furfural, improves the overall application of the PHL biomass. [ABSTRACT FROM AUTHOR]

Nowadays, afterglow materials with long-lifetime phosphorescence are mainly prepared from metal-containing substances. It is necessary and challenging to find a simple, green and feasible approach to generate afterglow materials with excellent phosphorescence from biomass materials. Herein, a facile strategy is proposed to construct afterglow materials via confining fluorescence carbon dots from lignin into silica (SiO2). Specifically, a microwave-assisted carboxymethylation process was adopted for the lignin precursor, which endowed the lignin with abundant carboxyl groups (3.69 mmol g−1) and maintained its benzene ring structure. Subsequently, N-doped lignin-based carbon dots (NL-CDs) with nanoscale size (6.07 nm) and excellent fluorescence (quantum yield = 30.6%) were prepared through the hydrothermal treatment of carboxymethylated lignin. Finally, the NL-CDs were confined in SiO2 and the generated NL-CDs@SiO2 exhibited excellent phosphorescence behavior in both solid-state and aqueous solution. The obtained afterglow materials achieved 5.97% of phosphorescence quantum yield and 834 ms of lifetime, which could be observed for 6 s by the naked eye. Meanwhile, a multi-modal information encryption strategy was designed based on the phosphorescence characteristics of the afterglow materials. The proposed strategy in this paper will pave the way to generate afterglow materials from lignin biomass and provide guidance for high-value utilization of lignin. [ABSTRACT FROM AUTHOR]

The predominant adhesives currently utilized in the wood sector are sourced from petroleum. However, it is crucial to acknowledge that fossil resources possess a limited supply, and their extraction procedures can lead to adverse effects on the ecosystem. Renewable biomass resources have important application prospects in wood adhesives. This paper reviews the recent research progress on utilizing biomass to replace or modify conventional petroleum-based adhesives, focusing on the application of tannin, lignin, protein, starch, and cellulose in urea–formaldehyde (UF), melamine, phenol–formaldehyde (PF), epoxy (EP), and polyurethane (PU) resin adhesives. The symbiosis of renewable biomass with conventional petroleum-based adhesives portends substantial advancements for the wood adhesive industry. This review evaluates the substitution capacity and modification effect of biomass, discusses its application prospects in the wood-based panel industry, and predicts the future direction of biomass in wood adhesives, providing new inspirations for the development of novel green adhesives. [ABSTRACT FROM AUTHOR]

The document is a table of contents for the journal "Green Chemistry," which focuses on cutting-edge research in the chemical industry to reduce environmental impact. The journal covers topics such as vinyl polymer degradation, bioenergy sources, carbon anodes for lithium-ion batteries, and lignin biorefinery. Published by The Royal Society of Chemistry, the journal aims to promote sustainable and environmentally friendly chemistry through articles on catalysis, organic compound synthesis, bioconversion, materials science, and environmental chemistry. The journal is available electronically. [Extracted from the article]

In this paper, we describe an approach for producing both high quality and high quantity of lignin through studying the structural change of lignin during treatment of poplar wood in γ-valerolactone (GVL) for a range of temperatures (from 80 to 120 °C) and reaction time at temperature (from 1 to 24 h). Various techniques, including nuclear magnetic resonance (NMR) spectroscopies (solution- and gel-state 1H–13C 2D HSQC and 31P) and gel-permeation chromatography (GPC) were applied to characterize the lignin structures. As the GVL-extracted lignin yield increases, the level of β-ether units decreases and the level of condensation products increases. The β-ether content, the aliphatic hydroxyl group content, and the molecular weight of the GVL-extracted lignin fractions were close to the poplar lignin from other preparation methods (e.g., enzyme lignin). A two-step hydrolytic process (120 °C, 2 × 15 min) gave a higher lignin yield (56.5% vs. 54.8%) with three times higher β-ether content (31.9% vs. 10.6%) than lignin extracted from a single-step process at 120 °C for 1 h. The results demonstrate that multiple-step cycling of cosolvent-assisted hydrolysis can help preserve more of the virgin ether-bond structures of GVL-extracted poplar lignin. Such a strategy can also be applied to a fully continuous-flow reactor system in future research to further improve both the productivity and quality of GVL-extracted lignin. [ABSTRACT FROM AUTHOR]

The catalytic pyrolysis of guaiacol-based lignin monomers, vanillin, syringol, and eugenol over commercial HZSM-5 has been investigated using operando Photoelectron Photoion Coincidence (PEPICO) spectroscopy to unveil the reaction mechanism by detecting reactive intermediates, such as quinone methides and ketenes, and products. Vanillin shares the decomposition mechanism with guaiacol due to prompt and efficient decarbonylation, which allows us to control this reaction leading to a phenol selectivity increase by switching to a faujasite catalyst and decreasing the Si/Al ratio. Syringol first demethylates to 3-methoxycatechol, which mainly dehydroxylates to o- and m-guaiacol. Ketene formation channels over HZSM-5 are less important here than for guaiacol or vanillin, but product distribution remains similar. C3 addition to guaiacol yields eugenol, which shows a more complex product distribution upon catalytic pyrolysis. By analogies to monomers with simplified functionalization, namely allylbenzene, 4-allylcatechol, and 4-methylcatechol, the eugenol chemistry could be fully resolved. Previously postulated reactive semi-quinone intermediates are detected spectroscopically, and their involvement opens alternative pathways to condensation and phenol formation. Allyl groups, produced by dehydroxylation of the β-O-4 bond, may not only decompose via C1/C2/C3 loss, but also cyclize to indene and its derivatives over HZSM-5. This comparably high reactivity leads to an unselective branching of the chemistry and to a complex product distribution, which is difficult to control. Indenes and naphthalenes are also prototypical coke precursors efficiently deactivating the catalyst. We rely on these mechanistic insights to discuss strategies to fine-tune process conditions to increase the selectivities of desired products by enhancing either vanillin and guaiacol or supressing eugenol yields from native lignin. [ABSTRACT FROM AUTHOR]

High-quality liquid biofuels can be produced from renewable lignin-derived phenolic compounds through an efficient hydrodeoxygenation (HDO) process in which the traditional catalysts usually include metal sites and acid sites that catalyze the hydrogenation and deoxygenation procedures respectively. This work presents a novel acid-free NixMoyN/C catalyst from the perspective of green chemistry providing a new pathway for HDO of lignin-derived phenolic compounds that involves hydrogenation deoxygenation and hydrogenolysis at the same time. A series of NixMoyN/C catalysts were prepared by varying the Ni :Mo molar ratio among which the Ni1Mo3N/C catalyst showed the best HDO performance. Guaiacol could be completely converted at 260 °C after 4 h with 95.8% cyclohexane selectivity. In addition a small amount of benzene could be obtained as a valuable fuel additive by-product by altering the conventional HDO reaction path. By shortening the reaction time benzene could be obtained as an intermediate product with a relative high selectivity. Based on the characterizations using XRD BET SEM TEM XPS H2-TPD and EPR, the results demonstrate that the multiple active components of the Ni1Mo3N/C catalyst allow it to efficiently catalyze the hydrogen activation and C--O bond cleavage even under acid-free conditions. The existence of the active phases of Ni Ni2Mo3N and β-Mo2C as well as the interaction between Ni and Mo metals together contributed toward efficient HDO performance. Not only for the various phenolic model compounds the feasibility of Ni1Mo3N/C catalysts for upgrading raw lignin oil was also demonstrated with the hydrocarbon content increasing from 5.7% to 88.4%. Notably arenes accounted for 18.2% of the hydrocarbon products which confirmed the occurrence of hydrogenolysis in the catalytic process. This work provides a novel route for the conversion of lignin-derived phenolic compounds to produce high-quality hydrocarbon liquid biofuels especially the direct production of arene components. [ABSTRACT FROM AUTHOR]

Pretreatment facilitates cost-effective operations on lignocellulosic biomass ranging from densification to deconstruction and bioproduct development. However, determining molecular-level mechanisms behind pretreatment and their effects has remained elusive. Here, we combine computational simulation and experiment to investigate the effects on wheat straw agricultural residue densification of an emerging pretreatment solvent, namely, a deep eutectic solvent (DES) consisting of choline chloride (ChCl) and oxalic acid (OA). Ab initio molecular dynamics indicates that dissociation of lignin from cellulose in lignin–carbohydrate complexes, which does not occur to a significant extent in aqueous solution, is favorable in the DES and occurs via cleavage of the guaiacyl : xylose ether bond linkage by OA. The ensuing hemicellulose removal exposes lignin to the DES which, molecular dynamics simulation indicates, leads to lignin expansion. The resulting changes in wheat straw fiber structure, lignin distribution, and functional group modifications upon DES treatment by scanning electron and fluorescence microscopy along with Fourier-transform infrared spectroscopy. The molecular expansion of lignin enhances inter-particle binding in wheat straw, leading to denser structures under pelletization. The resulting high mechanical stability and combustion properties make the wheat straw a suitable precursor of high-quality densified solids (e.g., solid biofuel). Overall, we shed light on the molecular-level mechanisms involved in DES pretreatment for biomass densification, demonstrated here in the development of a solid biofuel. The approach here illuminates the rational design from first chemical principles of methods to convert lignocellulosic resources into advanced materials. [ABSTRACT FROM AUTHOR]

It is known that wood releases low levels of formaldehyde under natural conditions, but the mechanism for this release has not been well explored. This paper presents the lignin-mediated Fenton (LMF) reaction as a newly described mechanism for the generation of formaldehyde from wood lignin in the presence of iron. Traditional desiccator methods with Nash reagent and fluorescence spectrophotometry, and a commercial electrochemical-based formaldehyde sensor were used to examine the effects of important components in the LMF reaction i.e., iron reductant, hydrogen peroxide and lignin, on the wood formaldehyde emission in the presence of iron. The results showed that low levels of iron, especially in its reduced ferrous oxidation state, promoted the generation of formaldehyde in the presence of lignin in wood. Experiments were also conducted with additional iron reductants and hydrogen peroxide, which demonstrated additional formaldehyde generation in the presence of ferric iron and lignin, suggesting active generation of formaldehyde from wood by the LMF reaction. [ABSTRACT FROM AUTHOR]

Life cycle thinking analysis (LCT) was conducted on the production of vanillin via bamboo wet air oxidation compared to vanillin production from crude oil or Kraft lignin. Synthetic vanillin has been produced from crude oil and paper pulping process "waste" for nearly a century. Bamboo is a quick growing, lignin rich biomass with the potential for the generation of aromatic products including vanillin. Wet air oxidation experiments were performed, using CuSO4 and Fe2O3 catalysts in alkaine environments, on raw bamboo with the purpose of determining the aromatic compound yields in order to investigate bamboo as a potential source of fine chemical products. From the LCT approach, production of vanillin from Kraft Lignin compared to crude oil has a lower environmental impact across all categories per kg produced of vanillin. Kraft lignin production of vanillin is shown to reduce smog formation and CO2 emissions from non energy sources to negligible levels while decreasing acidification potential by 6.8 times, toxic inhalation by 1.3 times and toxic ingestion potential by 0.3 times compared to crude oil. The proposed bamboo oxidation route has the potential to have the least environmental impact with negligible impact on smog formation potential and ozone depletion potential if a green polar extractive solvent can be utilised in future while also decreasing toxicity by inhalation by a further 115 fold and ingestion by 9458 fold. This work has the potential to contribute to the United Nation Sustainable Development Goal for Responsible Consumption and Production, Goal 12. [ABSTRACT FROM AUTHOR]

The dark color of industrial lignin is the main obstacle for their high value-added use in areas such as sunscreen or dyestuff dispersants. Here, a one-step method for reducing the color of lignin is presented and the structural changes of the whitened lignin are characterized by UV, FTIR, NMR, GPC, DLS, AFM, HS-GC and potentiometric titration. The results show that the content of aromatic ring, methoxyl and phenolic hydroxyl groups in the alkali lignin (AL) decreases, while the content of carboxylic groups increases when it is exposed to UV in THF. AL experiences a darkening process before it is gradually whitened. The blue shift of the UV spectrum and the decrease in size and molecular weight indicate AL is not only intermolecular and intramolecular disaggregated, but also partially depolymerized when light colored lignin is obtained. This simple but efficient whitening method is successfully practised in bleaching. The white degree of raw paper increases from 0.438 to 0.917 after being irradiated under sunshine for 3 days. [ABSTRACT FROM AUTHOR]

When attempting to obtain light-color lignin from lignocellulosic biomass or industrial lignin, the available options based on chemical or morphological modification suffer from low yield, high cost, and lack of availability at the required scales. In this study, we adopted a polyhydric-alcohol-based deep eutectic solvent (PA-DES) to directly extract light-color lignin from natural biomass, which is even whiter than native cellulolytic enzyme lignin (CEL). The isolated lignin possessed a high recovery yield (97.36%), regular micro-spherical morphology, enriched β-ether linkage of 58/100Ar, low phenolic hydroxyl content of 1.25 mmol g−1, minimal carbonyl content of 0.70 mmol g−1, and less condensed structures, thus yielding a lower content of chromophores. This lignin showed excellent sunscreen effects, which could enhance the SPF of a commercial sunscreen from 15 to 40 with only 5 wt% addition. This study can provide essential guidance for the scale-up production of light-color lignin and obtaining near-complete digestible cellulose for further saccharification. [ABSTRACT FROM AUTHOR]

Kraft lignin (KL), an abundant and underutilized biobased aromatic resource, was valorized into polyester vitrimers showing enhanced recyclability. KL was first modified with ethylene carbonate, to expose only highly reactive primary aliphatic OH groups, allowing the direct synthesis of polyester networks by polycondensation with PEG-based dicarboxylic acid. In addition to avoiding the use of toxic acyl halides or coupling agents, this fast synthetic process yields networks in which the amount of free OH groups can be easily controlled by adjusting the stoichiometry between COOH and OH groups. The presence of free OH groups allows transesterification reactions resulting in a vitrimer behavior. Increasing the number of free OH groups promotes the stress relaxation process, but does not affect the activation energy, which is relatively low compared to typical transesterification vitrimers, owing to the specific network topology. High performance materials with improved mechanical and chemical recyclability were clearly demonstrated. Besides, the modified lignin can be recovered and isolated in high yields with only minor changes in its chemical structure, offering further upcycling opportunities. This makes lignin, the first aromatic and biobased resource, a raw material that can also be recycled, in line with the concept of a circular bioeconomy. [ABSTRACT FROM AUTHOR]

Electrochemical catalysis emerges as a promising method for lignin depolymerization due to its environmental friendliness and mild reaction condition. Metal oxyhydroxides have displayed appealing electrochemical activity for the oxidation for various biomass substrates. In this study, we prepared different metal (Ni, Co, Mn, Fe, and Cu) oxyhydroxides on nickel foam electrodes through electrodeposition. Their electrochemical properties were characterized and the reactivity towards lignin oxidative cleavage was investigated using lignin model compounds. NiOOH exhibited significantly higher activity for oxidative cleavage of the β-O-4 linkage compared to other metal oxyhydroxides, resulting in a 93% yield of aromatic monomers with 99% selectivity towards benzoic acids. Furthermore, the reconstruction process of the active site NiOOH was revealed by in-situ testing, and the reaction mechanism was explored. The non-phenolic structure underwent Cβ–Cγ/Cβ–O or Cα–Cβ cleavage, predominantly producing benzoic acids, while the phenolic structure was rapidly oxidized into dicarboxylic acids over NiOOH. [ABSTRACT FROM AUTHOR]

Derived from lignocellulosic biomass, sustainable hard carbon has emerged as a promising low-cost anode material for sodium-ion batteries (SIBs). However, the intricate formation process of the hard carbon microstructure remains unclear. This study investigates the structural differences and pyrolysis behaviors of pine lignin and its graded variants obtained through a lignin molecular sieving engineering strategy. Moreover, it delves into the relationship between the microstructure of lignin-derived hard carbon and its sodium-ion storage characteristics. Pristine pine lignin, along with ethanol-isolated lignin, acetone-isolated lignin, and residual lignin, serves as a precursor for synthesizing hard carbon materials. Quantitative analysis via31P NMR spectroscopy reveals the highest content of polar functional groups in ethanol-isolated lignin. Interestingly, hard carbon derived from ethanol-isolated lignin exhibits the smallest closed pore volume, leading to the lowest plateau capacity of sodium-ion storage. Conversely, hard carbon derived from acetone-dissolved lignin displays the highest plateau capacity owing to its largest closed pore volume formed in the carbonization process. The origin of open and closed pore structures of hard carbons is thoroughly analyzed. [ABSTRACT FROM AUTHOR]

The utilization of plant polyphenols as catalyst carriers holds promise for environmentally friendly catalysis. However, challenges such as the inhomogeneous distribution of organic ligands often hinder their effectiveness. In this study, lignin–metal supramolecular framework were formed through ionic coordination self-assembly, achieved by oxidative ammonolysis modified lignin. The specific spatial domain-limiting effect of lignin–metal supramolecular framework ensures the dispersion and stability of catalyst active sites. Carbon-coated trimetallic catalysts (Ru–FeNi@OALC) derived from lignin–metal supramolecules exhibit promising performance, with low overpotentials for the oxygen evolution reaction (OER, η10 = 290 mV) and the hydrogen evolution reaction (HER, η10 = 52 mV), surpassing commercial noble metal catalysts. Additionally, these catalysts demonstrate long-lasting water-splitting performance, highlighting their potential for sustainable catalytic reactions. Molecular simulations and DFT theoretical calculations elucidate the feasibility of lignin oxidative ammonolysis modification and reveal the coordination mechanism. Furthermore, the abundant defects and disorder in the coordination polymer-derived carbon materials optimize electron transfer processes and accelerate reaction kinetics. This construction strategy towards designable polyphenol–metal supramolecular framework presents a promising avenue for the green synthesis of a variety of metal/carbon composite catalysts, contributing to sustainable catalysis and environmental protection. [ABSTRACT FROM AUTHOR]

Lignin, a crucial component of lignocellulosic biomass, holds immense promise for advancing biorefineries and producing sustainable energy alternatives. This study engineered a CN/rGO/BMO (2 : 1) heterojunction photocatalyst with varying Pd NP loading to selectively target the hydrogenolysis of challenging C–O ether bonds in lignin model compounds. Specific focus was on β-O-4, α-O-4, and the formidable 4-O-5 linkages. The 4-O-5 linkage, due to its high dissociation energy, poses a significant challenge. Electrochemical and spectral analyses unveiled improvements in charge separation, leading to delayed recombination of charge carriers in the heterojunction photocatalyst. Decorating the heterojunction with Pd NPs exhibited an elevated work function and a low Fermi energy level, facilitating the accommodation of photogenerated electrons and enabling efficient H2 dissociation. Such enhancement facilitated the cleavage of all three linkages, including the resistant 4-O-5 bonds under ambient conditions. The photocatalyst exhibited effective cleavage, yielding aromatic (toluene, phenol, ethylbenzene) and aliphatic (cyclohexane, ethylcyclohexane) products. Selectivity modulation was achieved by adjusting the time, hydrogen pressure, and Pd loading. Furthermore, this photocatalytic approach successfully transformed simulated lignin bio-oil containing all three linkages into valuable monomers. The alcoholic solvents efficiently harnessed photogenerated holes and prevented electron–hole recombination. The photocatalyst also demonstrated the capability to produce monomers from the native lignin extracted from teak wood sawdust. Emphasizing the focus on the reaction pathway and mechanism, scavenging studies and analyses were conducted, including UPS and VBXPS, to establish the Z-scheme charge transfer mechanism within the heterojunction. These findings provide a sustainable and efficient pathway for lignin valorisation in biorefineries, significantly contributing to the advancement of green fuels and aligning with the principles of green chemistry. [ABSTRACT FROM AUTHOR]

Upgrading lignin-derived monomeric products presents a compelling prospect for synthesizing value-added products. Despite the potential benefits, the conversion of lignin-derived phenols into hydroxytyrosol (HT), a potent natural antioxidant predominantly sourced from olives, remains underexplored. Herein, we envisioned three novel one-pot cascade biocatalytic approaches for converting lignin-derived catechol and phenol into HT by integrating four or five main reactions: C–C coupling, hydroxylation, decarboxylation, deamination and reduction. By co-expressing the corresponding enzymes in recombinant Escherichia coli (E. coli) resting cells, we achieved HT conversions of 65.4% and 89.0% from 10 mM catechol using recombinant E. coli (CFK-RTA) resting cells, which co-expressed tyrosine phenol-lyase (FnTPL), tyrosine decarboxylase (TDC), amine transaminase (ATA) and aldehyde reductase (yahK), and E. coli (RFK-EAL) resting cells, which co-expressed FnTPL, L -amino acid deaminase (LAAD), α-keto acid decarboxylase (ARO10) and yahK, respectively. Additionally, a 75.3% conversion of HT from 10 mM phenol was achieved with E. coli (CFK-EBC-RAL) resting cells co-expressing FnTPL, 4-hydroxyphenylacetate 3-hydroxylase (HpaBC), LAAD, ARO10 and yahK. The highest HT titers of 20.6 mM (3.18 g L−1) and 18.5 mM (2.85 g L−1) were obtained from 30 mM catechol and phenol, respectively, by utilizing recombinant E. coli (RFK-EAL) and E. coli (CFK-EBC-RAL) resting cells in a fed-batch strategy. These cascade biocatalysis processes rely on biomass-derived phenol or catechol and inexpensive pyruvate as substrates, with NH4Cl serving as the amine donor, offering new and viable routes for the sustainable and environmentally friendly production of HT. [ABSTRACT FROM AUTHOR]

Reductive catalytic fractionation (RCF) is a lignin-first biorefining technique that produces a polysaccharide-rich pulp and a lignin oil that is rich in aromatic monomers from aryl–ether bond cleavage and carbon–carbon linked aromatic oligomers. Separations of the lignin-derived monomers, both from one another and from the oligomers, out of these lignin oils could potentially yield high value co-products. To that end, we demonstrate that counter-current chromatography (CCC) is an effective means for simultaneous lignin monomer–monomer and monomer–oligomer separations using oils from RCF reactions with hardwood, softwood, and herbaceous feedstocks. Partition coefficient measurements of aromatic monomers from RCF of poplar, pine, and corn stover were first used to inform CCC solvent selection. We subsequently demonstrated CCC separations of those lignin oils using the HEMWat −3 solvent system and refined the measured partition coefficients using solute retention times and the cell utilized partitioning model to account for matrix effects in the following optimization experiments. Furthermore, the carbon–carbon linked oligomers in the lignin oil substrates elute together and separately from the aromatic monomers in lignin oil, resulting in an oligomer-rich product stream. Case studies of optimization of poplar RCF-derived lignin oil separations exhibited non-polar monomer yields of 95–99% with purities of 72–96%. Additionally, the same separation using a propyl-rich lignin oil produced from a H2-free RCF process showed a nearly 46% increase in normalized productivity, exhibiting the importance of tuning feed composition to improve separation performance. Taken together, this work shows that CCC is a promising method for simultaneous lignin monomer–monomer and monomer–oligomer separations. [ABSTRACT FROM AUTHOR]

Laser-induced graphene (LIG) is a versatile form of graphene materials synthesized through direct laser writing (DLW) onto a carbon-rich precursor. Lignin is a promising natural precursor for LIG. However, the lack of understanding of the relationship between lignin chemistry and LIG properties limits the effective utilization of lignin. Herein, we aimed to understand the structural evolution of lignin into few-layer graphene during direct laser writing via the combined experimental investigation and reactive force field molecular dynamics (MD) simulation. Strong correlations were found between structural features of lignin and LIG characteristics, especially the sheet resistance (electrical conductivity) and defects in graphene domains. Specifically, higher molecular weight lignin demonstrated a superior propensity for generating the graphitic structure in the turbostratic matrix of LIG. This phenomenon led to better graphene quality in terms of morphological continuity, conductivity, and graphene domains. The glass transition temperature (Tg) of fractionated lignin was identified to have the strongest linear correlation with both sheet resistance and defect density in LIG. Additionally, the MD simulations shed light on the role of closely positioned carbon atoms in the initial substrate, highlighting their facilitative effect on the formation of large graphene domains. The proposed LIG formation pathway offers a new avenue for lignin biorefinery, facilitating efficient production of graphene materials from renewable resources. [ABSTRACT FROM AUTHOR]

Lignin-containing cellulose nanofibrils are successfully produced after enzymatic treatment of curlinduced, unbleached kraft pulps. An enzyme cocktail composed predominantly of endoglucases but also containing xylanases, laccases, and lytic polysaccharide monooxygenases (LPMO's) results in significant enzyme-mediated fiber modification. A substantial (70%) reduction in pulp viscosity can be achieved while enzyme treatment of curl-induced fibers results in improved fibrillation and increased colloidal stability. This is likely due to the higher negative charge density (-57.5 mV) of the fibers. The enzymetreated, curl-derived cellulose nanofibrils show improved characteristics such as higher transmittance, lower viscosity, and thinner nanofibrils, resulting in enhanced nano-fibrillation. Superior mechanical properties, such as increasing the tensile strength of cellulose nanopapers to 150 MPa, are obtained as a result of the improved fibril network. The pre-curled fibers appear more accessible to enzyme treatment, resulting in cellulose nanofibrils with improved properties with less chemical treatments and mechanical refining energy required. [ABSTRACT FROM AUTHOR]

Research on zinc-ion hybrid supercapacitors has been gaining much attention due to the combination of their high energy and power density. However, the cost of preparation and poor rate performance of porous carbon cathode materials are two major issues limiting their large-scale utilization. In this study, we used nano calcium carbonate as the hard template agent and economical lignin as the carbon source to synthesize lignin-derived porous carbon with high specific surface areas and high mesopore ratios. Through a double decomposition reaction, calcium chloride produced by acid pickling is combined with sodium carbonate to create nano-calcium carbonate, thus enabling the regeneration of nano-calcium carbonate. More importantly, carbon dioxide resulting from the pyrolysis of calcium carbonate causes an internal activation effect on carbon materials, thus causing the formation of micropores and expanding the pore size of some micropores and small mesopores. Through this strategy, the specific surface area of lignin-derived porous carbon is up to 860.5 m² g-1, and the mesopore volume accounts for more than 90% of the total pore volume. The zinc-ion hybrid supercapacitor with lignin-derived porous carbon as the cathode displays an impressive capacity retention rate of 64% when the current density is increased from 0.1 to 20 A g-1. This work provides a green and sustainable route for the development of low-cost, high-rate performance porous carbon materials. [ABSTRACT FROM AUTHOR]

A sustainable lignin bioconversion depends on the exploitation of the inherent aromaticity of lignin for high-value aromatic products. However, the microbial valorization of lignin is hindered by the lack of established bioconversion routes or the inefficient heterologous expression of key enzymes. Here, an efficient biological lignin conversion route was constructed in a microbial cell factory by tapping the inherent aromaticity of lignin to produce aromatic natural compounds such as homoeriodictyol. The heterologous biosynthesis pathways were successfully constructed to convert lignin-derived monomers to homoeriodictyol in Saccharomyces cerevisiae. The implementation of combinatorial regulating strategies resulted in enhanced CoA supply, suppression of branch pathways, and upregulation of the rate-liming enzymes, which increased the titer of homoeriodictyol by a remarkable 22.5-fold. After that, engineering cofactor supply and recycling led to a substantial 95% increase in homoeriodictyol production. The rational design and modification of the heterologous rate-limiting enzymes helped achieve substantial improvement in the homoeriodictyol yield. All these strategies together enabled the record homoeriodictyol titer of 3.2 mmol l-1 from lignin derivatives by S. cerevisiae. Overall, such an innovative conversion route meets the atom-economy concept by converting lignin derivatives into valuable flavonoids, paving a green, sustainable way for both the valorization of lignin and the production of aromatic natural products. [ABSTRACT FROM AUTHOR]

Rigid lignin foam is prepared by a baking method using kraft lignin as the sole source. The eco-forming process involved cold-pressing kraft lignin powder into a solid block, heating the solid block to form lignin foam, and finally curing and cooling the lignin foam to obtain an open-cell, rigid foam. Both adsorbed water and water generated from the dehydration of hydroxyl groups in the lignin served as the blowing agent in this baking method. It was found that as the moisture content of lignin decreased, the foam densities increased, the mean bubble sizes decreased, and the bubble size distributions became narrower. Foam morphology showed an open cell structure and a wide cell volume distribution. The results suggest that controlling the moisture content in raw lignin allows for the control of the pore structure of the lignin foam. Based on their unique properties, lignin foam materials hold great promise in many applications especially as core insulation materials for structural insulated panels (SIPs). [ABSTRACT FROM AUTHOR]

Phenolic resins (PRs) are being widely used in many fields such as molding plastics, foams, coatings, and semiconductor packaging owing to their good properties including corrosion resistance, heat resistance, flame resistance, and electrical insulation properties. However, the traditional phenolic resins industry depends very heavily on petroleum as a source of phenol raw material, which is under the influence of petroleum reserves. In recent years, many studies have been conducted to develop cheap, abundant, renewable, and high-performance alternatives to phenol for the production of PR. Lignin, as the most abundant natural polyphenol, has similar chemical structures to that of phenol. Lignin has received increasing attention as a potential feedstock for renewable fuels and chemical production. The substitution of lignin for phenol can not only reduce the costs of PRs but also increase their performance, such as low-toxicity residues and environmental friendliness. This paper reviews the recent progress in lignin activation and modification for lignin-based phenolic resin (LPR) synthesis, highlights the different lignin modification methods, compares the performance of different LPR products, and summarizes their applications in adhesives, foams, molding powders, micro/nano-spheres, and other advanced materials. Finally, this review puts forward the current challenges and potential future prospects for LPR materials. [ABSTRACT FROM AUTHOR]

A novel method of cleaning waste lignin biomass by means of selective biodegradation of cellulose and hemicellulose is investigated. This method uses Pseudomonas fluorescens (P. fluorescens), a non-pathogenic bacterium capable of producing cellulolytic enzymes, cleaving polymeric carbohydrates into free sugars and utilizing them as their carbon source. The growth of P. fluorescens on lignin biomass was confirmed by increasing cell count with time and visualized by scanning electron microscopy (SEM). Depletion of free sugars in the growth medium was measured by Technical Association of the Pulp and Paper Industry (TAPPI) methods and by time-of-flight secondary ion mass spectrometry (ToF SIMS), which showed a significant decrease in the carbohydrate content and an increase in the lignin fraction after P. fluorescens biodegradation. The molar mass distribution of lignin before and after the biodegradation of carbohydrate impurities showed no indication of lignin depolymerization. Our results strongly support the biodegradation of carbohydrate impurities from waste lignin by P. fluorescens as an effective, green and eco-friendly process. [ABSTRACT FROM AUTHOR]

Lignin has been explored extensively as a renewable precursor for carbon materials, considering its abundance as a major component of plant cell walls and its sustainability as a byproduct of both lignocellulosic biorefinery and the paper-making industry. Despite the extensive efforts to define the process–property relationship, it remains largely unknown how lignin biosynthesis and its chemistry would impact the resultant carbon fiber properties, for both mechanical and electroconductive performances. Such inadequate understanding fundamentally limits feedstock design and selection to improve carbon fiber properties toward broader commercial applications. Using lignin from a broad range of biomass feedstocks for carbon fiber manufacturing, we have fundamentally explored the structure–function relationship between lignin chemistry and carbon fiber performance. Specifically, lignin extracted from hardwood (sugar maple), softwood (loblolly pine and red cedar), and herbaceous plants (corn stover and switchgrass) was used for carbon fiber manufacturing, considering the very different lignin structures from these feedstocks. Linear regression models were established to define the relationship between carbon fiber mechanical properties and lignin structural characteristics. The results highlighted that the content of β-O-4 linkages correlates significantly with the tensile strength and elastic modulus of lignin carbon fibers, indicating that more linear β-O-4 linkages would promote the carbon fiber mechanical performance. Moreover, electroconductive properties are essential for broader energy device application of lignin-based carbon fibers, yet the mechanisms controlling their electroconductivity are largely unknown. We hereby demonstrated that a higher β-O-4 content also promotes the electroconductivity of lignin carbon fibers. Microstructure analysis further revealed that the crystallite size and content of the pre-graphitic turbostratic carbon structure in lignin-based carbon fibers were enhanced as the β-O-4 linkages increased. The content of β-O-4 linkages has shown a strong correlation with the crystallite content in a linear regression model. This study thus revealed the underlying mechanisms regarding how the lignin structure in planta defines the resultant carbon fiber properties. Moreover, the study also highlighted the correlation between the mechanical and electroconductive properties of lignin-based carbon fibers, both of which were defined by the lignin structure. [ABSTRACT FROM AUTHOR]

Lignocellulose flow fuel cells are promising technologies for large scale generation of renewable electricity at low temperature. However, most of them have low electron transfer kinetics and require pre-reaction and redox mediators in anolytes for a liquid-phase catalytic reaction, which leads to low power density, energy consumption and resource waste. Herein, we develop a new low temperature and high-power density lignin flow fuel cell (LFFC) catalyzed by CoMn-LDH electrocatalysts with superhydrophilic intercalation on the anode to efficiently degrade lignin and transfer electrons rapidly. The experiments and DFT calculations show that CoMn-LDH exhibits high adsorption capacity for lignin due to its superhydrophilic intercalation, and has good electrical conductivity due to the greater overlap of antibonding orbitals and high continuity at the Fermi level. Moreover, the abundant oxygen defects of CoMn-LDH can depolymerize lignin effectively. Thus, the prepared CoMn-LDH electrocatalyst enables fast charge transfer and high catalytic efficiency. The power density of the designed LFFC reached 269.3 mW cm−2, and the generated electrical energy is 294.7 mW h based on 1.0 g of lignin, which are obviously higher than those of the reported LFFCs. Furthermore, it can work stably for more than 9 h at 0.3 V and 413.5 mA cm−2, and successfully power a 1.5 V LED pattern with only a 1 cm2 active membrane. It presents a promising approach for developing high-power density LFFCs towards a sustainable society. [ABSTRACT FROM AUTHOR]

It is critical to prepare self-supported carbonaceous electrode materials that enable high-mass loading and efficient ion/electron transport through a simple and sustainable method. Herein, for the first time, heteroatom-doped (O, N, and S) hierarchically porous thick bulk carbon is synthesized by carbonizing Pleurotus eryngii (PE) and lignosulfonate (LS) mixed precursors. After carbonization, the generated thick bulk carbon consists of interconnected macropores at the micrometer scale, with micropores and mesopores densely covering the pore walls. The carbon material displays a large specific surface area ranging from 315.5 to 960.2 m2 g−1 and is uniformly doped with O (14.8–19.1%), N (1.73–2.97%) and S (1.20–1.94%), endowing it with excellent ion transport and charge storage properties. As a result, the obtained thick bulk carbon electrode with a mass loading of 58.0 mg cm−2 achieves an outstanding capacitance of 25.0 F cm−2 (112.0 F cm−3) at 10 mA cm−3 and a superior rate capability of 14.3 F cm−2 (66.9 F cm−3) at 200 mA cm−3. The assembled symmetric supercapacitor device delivers a high areal energy density of 2.56 mWh cm−2 at a power density of 0.64 mW cm−2 with an excellent stability of 91.1% after 15 000 cycles at 50 mA cm−2. This facile and green synthesis strategy provides new carbonaceous electrode design concepts for high-energy-density storage. [ABSTRACT FROM AUTHOR]

The use of HZSM-5 and modified catalysts for the pyrolysis of lignin to produce aromatics has been extensively investigated. But certain limitations including catalyst deactivation and high-cost modifications still exist. A magnetic field (MF) was used to assist Fe and HZSM-5 catalytic lignin pyrolysis for aromatics production in this study. Product composition analysis revealed that the monocyclic aromatic hydrocarbon (MAH) and benzene, toluene, ethylbenzene, and xylene (BTEX) contents exhibited an upward trend in correlation with the MF intensity. The introduction of a MF significantly affects the improvement of the BTEX yield. Under the conditions of 80 mT MF intensity, 500 °C temperature and 50 mL min−1 carrier gas flow rate, the MAH and BTEX contents reach 32.94% and 27.19%, while the BTEX yield reaches roughly 19.55 mg g−1. Compared to no MF, these values rose by about 1.28, 1.36, and 1.94 times, respectively. Characterization results from XRD, XPS, TPO, N2 adsorption–desorption, and NH3–TPD tests showed that the MF facilitated the deoxidation and fragmentation of macromolecular oxygenates on the surface of Fe, promoting the ingress of smaller molecular compounds into the pores of HZSM-5 and boosting MAH production. Simultaneously, the MF impeded pore blockage in HZSM-5 and kept acidic sites from deactivating due to carbon deposition. This study lays a crucial groundwork for improving advanced technologies aimed at optimizing the utilization of organic solid waste. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) are widely used as recyclable green solvents for the separation of lignin from lignocellulosic biomass. However, the poor permeability of DES solution limits the green advancement of separation systems. In addition, lignin fragment molecules are susceptible to repolymerization reactions during separation, resulting in reduced lignin reactivity. In this study, a DES consisting of choline chloride (ChCl) as a hydrogen acceptor, 5-sulfosalicylic acid (5Saa) as a hydrogen donor, and a certain amount of γ-valerolactone (GVL) as an additive was designed. The system not only efficiently fractionated lignin from poplar (71.35%), but also selectively retained almost complete cellulose (retention 92.87%) under the optimal fractionation (ChCl/5Saa/GVL molar ratio 1/4/15, temperature 120 °C, time 3.0 h). Pre-crushing processing of raw materials was avoided as the new DES solution has stronger permeability compared to the previous DES solution. Selective deconstruction of lignocellulose was achieved due to a strong hydrogen network structure. The lignin fragments were effectively dissolved. The results showed that the stability of the carbo-positive active intermediates was enhanced by ChCl–5Saa/GVL. Lignin with a low molecular weight (2305 g mol−1), high purity (98.77%) and high total phenolic hydroxyl content (6.92 mmol g−1) was obtained. Homogeneous lignin nanoparticles (LNPs) were prepared with an average particle size of 23 nm. LNPs had high dispersion stability and excellent UV shielding properties. The green advancement of the new DES has been significantly improved and the efficient fractionation of high-value lignin was realized. [ABSTRACT FROM AUTHOR]

Lignin is composed of phenylpropyl alcohol through the C–O and C–C bonds, where β-O-4 accounts for the majority. Self-transfer hydrogenolysis (STH) is a promising method to produce valuable chemicals and fuels from lignin by cleaving the β-O-4 bond without exogenous hydrogen, but all the reported work used noble metal-based catalysts. In this work, a highly efficient Ni/C catalyst was derived from a Ni-containing metal–organic framework (Ni-MOF), and its self-transfer hydrogenolysis performance towards ether bonds in lignin model compounds was evaluated using 2-phenoxy-1-phenylethanol as a model compound in detail. It was found that the catalyst pyrolyzed under a nitrogen atmosphere at 500 °C (Ni-NDC-500) was very efficient for the reaction. Moreover, it could also catalyze the reaction of native lignin into monomers effectively without exogenous hydrogen. In addition, Ni-NDC-500 was recycled three times without an obvious reduction of the activity. [ABSTRACT FROM AUTHOR]

The global market of fossil carbon-derived adipic acid (AA) was over 3 million tons in 2022, emitting 3.1 million tons of the potent greenhouse gas N2O. Alternative biomass-derived feedstocks offer a sustainable option to replace fossil carbon, but alternative pathways for AA synthesis are also required to curb the substantial emissions associated with the process. A novel and sustainable approach to synthesize AA is by coupling biomanufacturing and electrocatalysis. Biologically-produced cis,cis-muconic acid (ccMA) from sugars and lignin monomers has recently gained significant attention as a precursor to AA, as it can be electrochemically hydrogenated to AA using water-derived (instead of fossil-derived) hydrogen and electricity generated from wind energy. For the first time in literature, we demonstrate appreciable electrochemical production of AA using supported palladium nanoparticles. The performance of this system contrasts with that of palladium foil or platinum-based catalysts, which produced little AA. Density functional theory calculations on model surfaces of palladium and platinum suggest that the reduction of ccMA to trans-3-hexenedioic acid occurs through an outer sphere proton-coupled electron transfer mechanism, while subsequent reduction to AA preferentially occurs on surface terrace sites. Our calculations also explain the exceptional performance of palladium nanoparticles compared to palladium- and platinum-based foils, attributing the more favorable activation energy barriers found on palladium terraces to the relatively moderate binding strength of adsorbed species. These results suggest structure-sensitive catalyst design strategies that maximize the exposure of terrace atoms for further improvement of the ccMA electrochemical hydrogenation process. [ABSTRACT FROM AUTHOR]

The electrochemical selective oxidative transformation of lignin feedstocks into valuable oxygenated aromatics is essential to establish a sustainable biorefinery. In this study, we used a rhombohedral ZnIn2S4 (R-ZIS) electrocatalyst to realise the efficient anodic cleavage of C-O bonds in benzyl phenyl ether (BPE), an a-O-4 lignin model compound, to a series of industrially relevant oxygenated mono-aromatics. The reaction occurred at +2 VAg/AgCl, 65 °C, and atmospheric pressure. In optimised conditions, the reaction achieved over 99% conversion rate with a Faraday efficiency of 51.6% at 91.3% conversion of BPE, that is greater than most known electrocatalytic oxidative cleavage examples. The ZnIn2S4 electrocatalyst was deposited on a carbon cloth support, and its structural properties and surface morphology were extensively investigated. Systematic potential controlled electrolysis coupled with 18O isotopic labelling confirmed that C-O scission occurred exclusively between the benzylic carbon and phenolic oxygen. Furthermore, substrate competition studies were conducted to compare the electrocatalytic performance of the R-ZIS catalyst with that of its structural analogue, hexagonal ZnIn2S4, in terms of BPE and monoaromatics conversion. The experimental results were supported by density functional theory calculations. The substrate scoping study revealed the suitability of the R-ZIS induced electrocatalytic system for a variety of substituted a-O-4/ß-O-4 model dimers. Overall, this work demonstrates an efficient anodic process that can enable the atom-efficient valorisation of lignin to produce oxygenated aromatics. The proposed approach can complement the numerous existing reductive lignin cleavage methods. [ABSTRACT FROM AUTHOR]

Solvents with integrated functions enable directional lignin valorization for producing value-added chemicals or lignin polyols. In this study, a solvent-triggered directional lignin valorization process was developed based on the design of a biphasic deep eutectic solvent/dichloromethane (DES/DCM) system. The designed solvents exhibit a combined feature of chemical stabilization from ethylene glycol-based-DES and physical stabilization from a biphasic system. By establishing the DES/DCM, lignin was effectively functionalized into lignin polyols with high yield. Furthermore, by implementing a simple recycling procedure of the DCM phase, the reaction pathway was switched, leading to depolymerization and stabilization of the stabilized lignin polyols. This process resulted in an almost threefold increase in monomeric acetal yields. The effect of biphasic DES on functionalization or switched depolymerization of lignin was confirmed through model compound studies. Our findings demonstrate a directional lignin valorization route using the designed biphasic DES system, which offers potential applications in the production of value-added aromatic chemicals or potential intermediates for polymers. [ABSTRACT FROM AUTHOR]

The global forest industry is focused on developing waste valorization technologies. Regional resources use in biorefineries could be a strategy to improve profitability and mitigate the environmental impact of the involved industrial sectors, adding a new value chain to the forest industry. This study develops the mass and energy balance for bioethylene and lignin production from industrial pine sawdust (IS), a primary wood processing in Argentina. The proposed production process is composed of: (i) sodaethanol pretreatment to remove the lignin; (ii) simultaneous saccharification and fermentation (SSF) to convert the cellulose to glucose and then to ethanol; (iii) ethanol recovery (95%); (iv) ethanol dehydration to bioethylene and; (v) bioethylene recovery through an ethylene tower and stripper. In the proposed process, 107 kg of bioethylene per ton of dry sawdust could be obtained, recovering 208 kg of lignin. Energy consumption is about 1885 MW h t-1 of dry sawdust. The highest consumption is in pretreatment and ethanol recovery processes, which can be reduced by 42%. Regarding economic assessment, the internal rate of return (IRR) and net present value (NPV) were 10.08% and 5.21 MM USD, respectively. Sensitivity analysis shows that the most influential parameters are lignin and bioethylene market prices and energy and enzyme costs. [ABSTRACT FROM AUTHOR]

Solvents play a critical role in the lignin hydrogenation process. However, elucidating the role of solvents in lignin hydrogenation solely through experimental methods presents considerable challenges. The present report integrates experimental results, quantum chemical calculations, and molecular dynamics simulations to study the effect of solvents on the hydrogenation of lignin on Ru/C to produce phenolic compounds. Solvents not only disperse the substrate and promote the mass transfer process in the hydrogenation reaction, but also significantly affect the hydrogenation reaction rate of lignin. We show that the hydrogenation reaction rates of lignin in different solvents differ by an order of magnitude (isopropanol > methanol > water > γ-valerolactone > tetrahydrofuran). By innovatively combining quantum chemical calculations with experimental results, it was reported for the first time that solvent affects the free energy barrier by regulating the properties of the transition state (C–O bond strength), thereby affecting the lignin hydrogenolysis reaction rate. Based on molecular dynamics simulations, this study investigated the interaction between lignin and various solvent molecules. The research results confirmed that solvent molecules regulate the solvent shell on the surface of lignin, thereby influencing the mechanism of the hydrogenation reaction process. [ABSTRACT FROM AUTHOR]

It is generally believed that the formation of lignin-based carbon quantum dots (L-CQDs) includes lignin depolymerization and repolymerization. However, the detailed mechanism has not been well understood. In this study, the effect of lignin molecular weight on the properties of L-CQDs is studied to elucidate the formation mechanism of L-CQDs. Firstly, alkaline lignin is sequentially fractionated into five lignin samples with a molecular weight range of 7100–2000 using a continuous organic solvent precipitation method. Then, the five lignin fractions are used to prepare five L-CQDs numbered from 1 to 5, corresponding to the lignin fractions from high to low, respectively. L-CQDs-3 that was prepared from the lignin fraction with an intermediate molecular weight of 5042 g mol−1 has a 1.86-fold increase in fluorescence intensity compared to the L-CQDs-0 prepared from pristine alkaline lignin. It is found that this lignin fraction with a molecular weight of 5042 g mol−1 can depolymerize into a large number of vanillin and benzaldehyde (2,4-dihydroxy-6-methyl) units. These low molecular weight units can easily form highly conjugated carbon core structures, thus improving the fluorescence performance of L-CQDs-3. In addition, the present study confirms the excellent imaging ability of L-CQDs-3 in the L02, HepG2 and Escherichia coli cells. This study not only supplements the existing L-CQD formation mechanism, but also provides a simple method for the preparation of L-CQDs with high fluorescence performance. [ABSTRACT FROM AUTHOR]

The catalytic conversion of lignin into heterocyclic aromatic compounds holds significant promise not only for expanding lignin's utility in pharmaceutical synthesis but also for imparting luminescent properties to downstream lignin products. However, the challenge lies in devising compatible catalytic conditions for selectively cleaving aromatic ether bonds and forming C–N bonds. In this study, we present a new approach to synthesizing functionalized carbazole derivatives from lignin phenolic β-O-4 model linkages using a one-pot, two-step method. Through a [3 + 1 + 2] benzene cyclization reaction involving lignin β-O-4 model compound, indole-3-carbaldehyde, and 3-chloropropiophenone catalyzed by cost-effective CuCl2·2H2O, we achieved yields of carbazole derivatives up to 90%, highlighting the economic viability of our approach. Our protocol is versatile, accommodating various reaction conditions, including selective cleavage of the C–O bond, aldol condensation, dehydrochlorination of β-chloro ketones, Diels–Alder addition, and dehydroaromatization reactions. Additionally, the resulting carbazole derivatives exhibit favorable twisted-intramolecular charge transfer (TICT) and aggregation-induced emission (AIE) effects. This method offers a sustainable and practical strategy for synthesizing lignin-based carbazoles, with economic advantages in terms of the catalysts and precursors, thereby advancing lignin's application in luminescent materials. [ABSTRACT FROM AUTHOR]

Producing green carbon fiber from lignin is not only attractive to biorefineries for valorizing lignin but also contributes to the decarbonization of multiple industries. However, the difficulty of obtaining high-quality lignin-based carbon fibers at low cost remains the bottleneck and barrier to its commercial application. Previous approaches for chemically modifying lignin or blending with co-precursors were ineffective in delivering the carbon fiber with the desired quality. We discovered that introducing thermo-mechanochemistry of lignin to carbon fiber processing is a facile and green approach to overcome this challenge. Thermo-mechanochemistry can be introduced by properly integrating thermal heating and mechanical tension force applied to the spun fiber, which can manipulate the ordinary lignin chemistry to control the microstructure evolution from lignin. Under the influence of this newly known chemistry, lignin can transform into an oriented structure that can easily be graphitized at low temperatures. In this work, three precursors consisting of lignin or lignin blends were used to produce the carbon fibers with average tensile strength and modulus of 2.45 GPa and 236 GPa, 2.11 GPa and 215 GPa, 2.2 GPa and 225 GPa, respectively, using a surprisingly low carbonization temperature of only 700 °C. The preliminary techno-economic analysis suggests a low production cost. The discovery of the thermo-mechanochemistry of lignin will alter perceptions of lignin-based carbon fibers and provide opportunities to produce commercially viable low-cost green carbon fibers, advancing lignin valorization. [ABSTRACT FROM AUTHOR]

The utilization of lignin in material fabrication has garnered significant attention despite its complex structure that greatly limits its applications. This study reports a green method for grading and modifying lignin to prepare stable hydrophobic coatings via the solvent/anti-solvent (ethanol/water) self-assembly method. First, the formic acid lignin particle (FLP) is prepared and the underlying mechanism is primarily ascribed to the hydrogen bonding, π–π interactions among aromatic groups within and between molecules, and hydrophobic interactions. The lignin nanoparticles were utilized to chelate with metal ions (iron) in order to obtain the stable hydrophobic coatings using the special nanostructures of FLP. This hydrophobic coating could be applied to different substrates (blocks, straw, and fabric). The cotton fabric exhibited an initial water contact angle (WCA) that increased from 73.4° to 129.6°, and excellent chemical and physical hydrophobic performance. Moreover, this coating has strong self-cleaning ability and could be used for oil–water separation. In this newly proposed fabrication, ethanol can be recovered in the preparation of lignin nanoparticles, which makes the green and facile preparation of a stable hydrophobic coating possible. Additionally, this work is important in upgrading formic acid lignin by controlling the polarity into value-added hydrophobic materials via green classification. [ABSTRACT FROM AUTHOR]