Lignin Samples Research Articles

Lignin Molar Mass Estimation by Dispersion Analysis.

Lignin's complex and heterogeneous molecular structure poses significant challenges for accurate molar mass determination, which is important for its utilization in industrial applications, such as biochemicals, nanoparticles, biobased binders, and biofuels. This study evaluates the potential of Taylor Dispersion Analysis (TDA) for measuring lignin size and compares it with size-exclusion chromatography (SEC) and diffusion-ordered spectroscopy (DOSY) NMR. Using dual Gaussian fitting, flow-induced dispersion analysis (FIDA), a TDA-based method, successfully determined the average hydrodynamic radii of multiple species in solvent-fractionated soda grass lignin samples, producing results consistent with DOSY. Molar mass calibration enabled comparisons between FIDA and SEC, revealing similar relative differences across lignin fractions. FIDA offers advantages such as rapid analysis and absence of stationary phase interactions, however its accuracy is limited by the variability of lignin fluorescence. Addressing these limitations will be critical for advancing FIDA as a method for lignin size estimation.

Co-Pyrolysis of Plastic Waste and Lignin: A Pathway for Enhanced Hydrocarbon Recovery

Various plastics and biomass wastes, such as polypropylene (PP), low- or high-density polyethylene (LDPE/HDPE), and lignin, have become some of the most concerning wastes nowadays. In this context, this study aimed to investigate the possibility of applying thermochemical processes for the valorization of these materials. The experiments were carried out using a thermogravimetric analyzer on individual plastic and lignin samples and their mixtures at different mass ratios of 1:1, 1:2, 1:3, and 1:4. The gaseous products evolved during the pyrolysis process were analyzed by combined thermogravimetric and Fourier-transform infrared spectroscopy (TG-FTIR) and chromatography-mass spectrometry (Py-GC/MS) to analyze the functional groups and chemical composition of the obtained pyrolysis products. The results showed that the main functional groups of lignin monitored by TG-FTIR were aromatic and aliphatic hydrocarbons, while all plastics showed the same results for hydrocarbons. The investigation confirmed that mixing these types of plastics with lignin at different mass ratios led to increased recovery of higher-value-added products. Py-GC/MS analysis showed that the greatest results of compound recovery were achieved with lignin and LDPE/HDPE mixtures at 600 °C. At this temperature and with a mass ratio of 1:3, the plastic’s radicals enhanced the depolymerization of lignin, encouraging its wider decomposition to hydrocarbons that can be applied for the production of value-added chemicals and bio-based energy.

Photocatalytic carboxylation of aromatics and lignin sample with CO2 over tubular hierarchical double heterojunction C/N-In2O3/ZnIn2S4

Photocatalytic carboxylation of aromatics and lignin sample with CO2 over tubular hierarchical double heterojunction C/N-In2O3/ZnIn2S4

Influence of Nitrogen Doping and Pre‐Carbonization on the Performance of Lignin‐Derived Activated Carbon for Supercapacitor Applications

AbstractNanostructured carbons are widely used as active materials for supercapacitor applications owing to their high specific surface area and electrical conductivity. Biomass waste‐derived materials can be sustainably produced. In this work, highly porous activated carbon was prepared from lignin waste for supercapacitor applications, and the effects of nitrogen doping and a pre‐carbonization treatment on the final performance were investigated. Particularly, activated carbonized lignin (ACL) and activated lignin (AL) samples were prepared with or without a pre‐carbonization step, respectively, and with or without nitrogen doping. Nitrogen doping of the samples was found to decrease the capacitance owing to the loss of critical oxygen‐containing functional groups, which provide pseudocapacitance. Meanwhile, the use of a pre‐carbonization treatment greatly improved the surface area and capacitance of the materials. Sorptometry analysis indicated that ACL and AL have high specific surface areas of 3174 and 2289 m2 g−1, respectively. ACL achieved a specific capacitance of 306.4 F g−1 and 292.1 F g−1 in 1 mol L−1 KOH and H2SO4, respectively. Furthermore, the contribution of a pre‐carbonization treatment to improve the surface area and maintain the presence of oxygen‐containing functional groups was identified as beneficial towards improving the pseudocapacitance properties of the porous carbon materials.

Atomistic Simulations of Mechanical Properties of Lignin.

The mechanical properties of lignin, an aromatic heteropolymer constituting 20-30% plant biomass, are important to the fabrication and processing of lignin-based sustainable polymeric materials. In this study, atomistic simulations are performed to provide microscopic insights into the mechanics of lignin. Representative samples of miscanthus, spruce, and birch lignin are studied. At room temperature below the glass transition temperature, the stress-strain curves for uniaxial compression and tensile loading are calculated and analyzed. The results show that lignin possesses rigidity with a Young's modulus in the order of GPa and exhibits strain hardening under strong compression. Meanwhile, lignin is brittle and fails through the microscopic mechanism of cavitation and chain pullout under local tensile loading. In addition to the three common lignin samples, minimalist model systems of monodisperse linear chains consisting of only guaiacyl units and β-O-4 linkages are simulated. Systematic variation of the model lignin chain length allows a focused examination of the molecular weight effects. The results show that the molecular weight does not affect the Young's modulus much, but higher molecular weight results in stronger strain hardening under compression. In the range of molecular weight studied, the lignin chains are not long enough to arrest the catastrophic chain pullout, explaining the brittleness of real lignin samples. This work demonstrates that the recently modified CHARMM force fields and the accompanying structural information of real lignin samples properly capture the mechanics of lignin, offering an in silico microscope to explore the atomistic details necessary for the valorizaiton of lignin.

Fabrication of biodegradable polyvinyl alcohol-based plastics toward technical lignin valorization

The fabrication of composite materials from lignin has attracted increasing attention to reducing the dependence of petrochemical-based resources on carbon neutrality. However, the low content of lignin in the biocomposites remains a challenge. Herein, industrial lignin is fractionated by an organic solvent to reduce its structural heterogeneity. Subsequently, the fractionated lignin samples are integrated with polyvinyl alcohol (PVA) to fabricate plastics characterized by uniform thickness and smooth surfaces. The resultant composite films exhibit tensile strength and strain up to 75 MPa and 1050%, respectively, which surpass state-of-the-art lignin-based bioplastics. The mechanism investigations reveal that the enhanced mechanical properties are due to the internal non-covalent interactions derived from the hydroxyl groups of lignin and PVA. Notably, the PVA/lignin films are biodegradable after 92 days' burial in soil. This study paves the way for the rational design of lignin-based biodegradable polymers as sustainable alternatives to conventional plastics.

Boron Lewis Acid Extraction of Wood Generates High Quality Lignin.

The separation of lignocellulose into lignin, cellulose, and hemicellulose without significantly altering the chemical structures of these component biopolymers remains a modern chemical challenge. Lignin, in particular, has potential as a highly valuable feedstock material but remains underutilized due to the difficulty of generating lignin with low modification and condensation. This work investigates the lignin-rich solids ("boron lignin") generated from a previously reported boron Lewis acid-mediated lignocellulose separation and concludes that (1) boron Lewis acid extraction removes 80-85% of carbohydrates from the original lignocellulose sample, and (2) the resulting lignin possesses a low condensation level and high similarity to native lignin structure. Residual carbohydrate assessment, depolymerization efficiency analyses, heteronuclear single quantum coherence (HSQC) and solid-state nuclear magnetic resonance (NMR) analyses are discussed, including benchmarking results with alternate lignin sources known to possess low and high condensation levels. Further, two different wood sources (white pine, a softwood, and beechwood, a hardwood) were employed to generate lignin samples. Depolymerization of a white pine-derived boron-lignin produced 47% (±9.5) of extractable monomers, which compares well to a state-of-the-art method to generate low condensed lignin (56 ± 7.8%). An unexpected instability of the oil sample was observed following hydrogenolysis of boron lignin generated from beechwood. Dramatic color changes coupled with precipitation and lowered monomer yields were observed when samples were aged (11% decrease) or concentrated (30% decrease). Based on NMR spectroscopic analyses, this instability is postulated to arise due to boron-mediated demethylation of methoxy sites on the lignin scaffold.

Evaluation of safety and biomedical potential of water-soluble oat lignin Avena sativa L.

The study of the value of lignin for biomedical use is generating growing interest. For the first time, the safety and biological efficacy of lignin from the stems of the oat Avena sativa L. were studied, necessary for a preliminary assessment of its biomedical potential, have been studied. In vitro experiments, a sample of oat lignin exhibited cytotoxicity to the HeLa, A549, and HT-29 cancer cell lines, depending on the concentration. At maximum concentrations 125 and 150 μg/ml, it reduced their survival and increased the level of reactive oxygen species. In vivo experiments, a sample of oat lignin, with acute (from 5 to 250 mg/kg body weight) and chronic (300, 1200 and 2000 mg/kg body weight) administration, did not have a toxic or genotoxic effect on the organs of mice. The biological efficacy of the oat lignin was manifested in activation of repair processes in bone marrow and thyroid gland, a decrease in the level of abnormal spermatozoa in males, stimulation of reproductive performance of females and in increase in research activity and a decrease in the level of anxiety in animals. The results indicate the prospects for further study of the medical and biological potential lignin of the oat.

Surface wettability of lignin materials from supercritical water hydrolysis of wood

To meet the demands of the evolving circular economy, there is a growing need for renewable resources as base materials for innovative, easily recyclable products. Lignin, the second most abundant biopolymer, has emerged as a promising source of aromatics and reinforcing agent in polymer composites. For the successful manufacturing of homogeneous composite materials, good bonding between the coexisting phases is essential to prevent the formation of voids and agglomerates. Therefore, understanding the surface properties of these materials is crucial for designing optimal composite compounds. In this study, the wettability of lignin-cellulose composites and lignin samples obtained through supercritical water hydrolysis (SCWH) of birch wood is investigated. The contact angle (CA) technique, specifically the sessile drop method, was employed to assess and compare the wettability of SCWH lignin with commercially available lignin and raw birch wood. The results provide insights into their surface energy, adhesion, and hydrophilic or hydrophobic characteristics under processing conditions. All samples exhibited hydrophilicity, with an initial CA approximately 40 °, except for raw birch wood, which had a higher initial CA of ∼ 64°. Notably, when lignin is accompanied by significant amounts of cellulose, different trends in CA changes over time were observed. The influence of pressure on the CA between water and these polymers was also analyzed, but no significant impact was detected. This research advances the development of lignin-based materials with tailored surface properties for various industrial applications.

Modulation of improved lignin structure for conversion of iron oxides on the metal artifact

This research reveals the structural analysis and antioxidant properties of unmodified ethanol organosolv lignin (AH EOL) and modified ethanol organosolv lignin (AHD EOL and AHPB EOL) upon incorporation with 1,5-dihydroxy naphthalene and p-benzoquinone, respectively. The extracted lignin derived from OPF was then evaluated with FTIR NMR, GPC, thermal analyses (TGA and DSC), solubility test, and antioxidant activity. Modified ethanol organosolv lignin incorporated with p-benzoquinone (AHPB EOL) exhibited the smallest lignin matrix, which leads to the highest water solubility and antioxidant activity compared to other ethanol organosolv lignin (EOL) samples (D% AHPB EOL: 24.25 ± 0.13 % > D% AHD EOL: 22.50 ± 0.16 % > D% AH EOL: 20.50 ± 0.22 %). The extracted EOL samples derived from OPF were then utilized in a preliminary rust conversion study of a metal artifact, which indicated that 7 wt% AHPB EOL possessed the highest RT% with 88.81 ± 0.14 %. The XRD and surface analysis of the treated rust also showed that it had transformed the archeological rust into an amorphous phase.

Isolation of β-O-4-Rich Lignin From Birch in High Yields Enabled by Continuous-Flow Supercritical Water Treatment.

The continuous flow supercritical water (scH2O) treatment of Birch wood (T=372-382 °C; t=0.3-0.7 s; p=260 bar) followed by alkali extraction of lignin allowed for the isolation of lignin and lignin carbohydrate complexes (LCCs) with a high number of β-O-4 moieties in the range 29-57/100 Ar (evaluated by quantitative 13C NMR analysis) in yields ranging between 13-19 wt % with respect to the initial wood. A "lightning rod effect" of carbohydrates has been claimed to explain the low degradation of β-O-4 bonds during the process. The structure of the isolated lignin was thoroughly elucidated via comprehensive NMR studies (HSQC, 13C and 31P). A low degree of condensation (DC)<5 % was found for all the lignin samples, which was only slightly dependent on the reaction severity. The number of aliphatic -OH, phenolic -OH, and -COOH groups was in the range 3.37-5.25, 1.41-2.31 and 0.39-0.73 mmol/g, respectively. The number of -COOH groups increased with increased severity, suggesting that oxidation can occur during the scH2O treatment. Furthermore, by simply varying the reaction severity, it was possible to tune important lignin properties, like the molar mass and the glass transition temperature (Tg).

Polymerized lignin based carbon nanofiber for high-performance energy generator and storage

It is a challenge to develop simple and efficient methods to optimize the lignin structure for preparing high-performance lignin-based carbon nanofibers (CFs). Herein, a novel and effective strategy for preparing high-performance lignin-based CFs is designed. Lignin samples with different chemical structures are prepared by polymerization modification and fractionation. This strategy completely gets over the dependence on petroleum-based polymers in the electrospinning process, and makes the lignin-based CFs show good performance in energy storage, temperature sensor, and moisture power generators. The specific capacitance and energy density of lignin-based supercapacitors reach 357.2 F/g and 31.5 Wh/kg, respectively. The CFs exhibit good flame retardancy and thermal sensitivity (about 1 s). In addition, moisture power generators assembled with CFs exhibit great potential. The output voltage of moisture power generators has a linear relationship with the number of devices. With the increase of series equipment, the output voltage of 5 series connected moisture power generators reaches 4.7 V. This work provides a new approach to prepare high-performance lignin-based CFs, which has a good application prospect in the fields of energy storage, sensor and power generation.

Controlled chemical transformation of lignin by nitric acid treatment and carbonization

This study focuses on understanding the chemical reactions and results of Kraft lignin transformation through nitric acid treatment and subsequent carbonization. With its rich carbon content, lignin stands out as a promising candidate for the manufacturing of high-value carbon materials. The lignin underwent effective nitration, depolymerization, and oxidation under ambient conditions and at 40 °C, while a slight increase in reaction temperature significantly reduced the reaction time. The molecular weight Mw was effectively reduced from 4371 g/mol to 767 g/mol. The acid-treated lignin samples with incorporated nitro groups were further carbonized to create nitrogen-doped carbon structures. The resulting materials show stable nitrogen content (about at 5 wt%) even after carbonization due to the transformation of nitro groups into thermally stable pyridinic moieties, thereby exhibiting enhanced electrocatalytic properties compared to nitrogen-free carbon materials derived from Kraft lignin. The nitric acid-assisted treatment of lignin obviates the need for catalysts, and additional extraction or purification steps for preparing bio-derived carbon precursors, rendering it facile, fast, and cost-efficient.

Preparation of structural colors from lignin: Improving the homogeneity between different raw materials by solvent precipitation fractionation

Structural color materials prepared by lignin colloidal spheres (LCSs) have attracted great interest due to their biocompatibility, biodegradability, multifunctionality, and ability to weaken incoherent scattering. However, the lignin raw materials originating from different biomass resources have distinct heterogeneity leading to a big difference in the size of resultant LCSs via self-assembly, which is a major challenge for the preparation of stable structural colors. In this work, we employ the solvent precipitation method to fractionate the crude lignin samples obtained from corncob, softwood, hardwood, and bamboo, respectively. After solvent precipitation fractionation, the self-assembly behaviors of different lignin samples become similar. The LCSs prepared by fractionated lignin samples show quite similar sizes (212, 202, 215, and 210 nm) compared with the LCSs prepared by crude lignin samples (341, 83, 128, and 253 nm). The quantitative atomic force microscope force spectroscopy demonstrates the improved homogeneity of LCSs prepared by fractionated lignin samples is attributed to similar long-ranged intermolecular forces in self-assembly. By employing LCSs as building blocks, the lignin-based pigments with stable structural colors are successfully prepared. The presented colors are independent of the biomass resource types, which benefits the product stability and large-scale production of lignin-based structural color materials.

Research on modeling the lignin waste molecular structure and pyrolytic reactions using ReaxFF MD method

The lack of clarity in characterizing the chemical structure model of lignin waste hinders the comprehensive understanding of its pyrolysis reaction mechanism. The characterization results revealed that the de–alkalized lignin sample contained larger amounts of aliphatic and aromatic carbons compared to carbonyl carbons. Additionally, the aliphatic carbon molecules exhibited a higher presence of oxygenated carbons. The degree of aromaticity (fa) was determined to be 63.93 %. The resulting single–molecule structural model exhibited a molecular formula of C33H26O11 and a molecular weight of 598.56. Furthermore, the evolutions patterns and formation pathways of primary volatile components (H2, CH4, CO, and CO2) in pyrolysis reactions were revealed. The number of H2 molecules exhibited a positive correlation with the rise in pyrolysis reaction temperature. CH4 molecules exhibited a pattern of initially increasing and subsequently decreasing. The number of CO molecules exhibited a positive correlation with the rise in pyrolysis temperature. Conversely, the number of CO2 molecules demonstrated an initial increase followed by a decrease as the pyrolysis temperature increased. Finally, the generation pathway analysis of pyrolysis products shows that the H2 molecule is composed of two hydrogen atoms bonded together that have been dissociated from the carboxyl group. Alternatively, it can be produced through hydrogenation reactions involving hydrogen atoms detached from the carboxyl group and methyl groups. CH4 is primarily generated through the reaction between –CH3 and free hydrogen ions. CO is primarily produced through the cleavage of the carbonyl group. CO2 is primarily produced through the cleavage of carboxyl and ester groups.

Insights into the Chemical Structure and Antioxidant Activity of Lignin Extracted from Bamboo by Acidic Deep Eutectic Solvents.

Deep eutectic solvents (DESs) composed of choline chloride as hydrogen bond acceptors (HBAs) and six organic acids as hydrogen bond donors (HBDs) were used to extract lignin from bamboo (Phyllostachys edulis (Carrière) J. Houz.). The structures of the DES-extracted lignin samples were analyzed by Fourier-transform infrared spectroscopy (FT-IR), UV-visible spectroscopy (UV-vis), thermogravimetric analysis (TG), and gel permeation chromatography (GPC) to investigate the relationship between the chemical structure of lignin and its antioxidant activity. The results showed that DES treatment removed a large portion of the lignin (73.37-86.38%) from bamboo, and the chemical structure of lignin was changed due to the use of different types of HBDs. The extracted lignin exhibited good UV-vis light shielding properties, thermal stability, and antioxidant activity. Moreover, the total phenolic hydroxyl content of lignins was positively correlated with their antioxidant activity, while the molecular weight of lignins was negatively correlated with their antioxidant activity. Notably, lignin extracted with choline chloride-p-toluenesulfonic acid had the highest phenolic hydroxyl content and lower molecular weight, showing the strongest antioxidant activity (IC50DPPH = 417.69 μg/mL, IC50ABTS = 58.62 μg/mL). This study confirms the high thermal stability, excellent antioxidant activity, and UV shielding properties of lignin extracted with choline chloride-organic acid DESs, suggesting its potential application in the fields of antioxidants and material modifiers.

The presence of nanoparticles in aqueous droplets containing plant-derived biopolymers plays a role in heterogeneous ice nucleation.

Organic matter can initiate heterogeneous ice nucleation in supercooled water droplets, thereby influencing atmospheric cloud glaciation. Predicting the ice nucleation ability of organic matter-containing cloud droplets is challenging due to the unknown mechanism for templating ice. Here, we observed the presence of nanoparticles in aqueous samples of known ice-nucleating biopolymers cellulose and lignin, as well as in newly identified ice-nucleating biopolymers xylan and laminarin. Using our drop Freezing Ice Nuclei Counter (FINC), we measured the median ice nucleation temperature (T50) of xylan and of laminarin droplets of 2 μl to be -14.2 and -20.0 °C, respectively. Next, we characterized these samples using nanoparticle tracking analysis, and we detected and quantified nanoparticles with mean diameters between 132 and 267nm. Xylan contained the largest nanoparticles and froze at higher temperatures. Xylan also dictated the freezing in a 1:1:1:1 mixture with cellulose, lignin, laminarin, and xylan. Filtration experiments down to 300 kDa with the xylan sample indicated that the presence of nanoparticles triggered freezing. Overall, only samples with mean diameters above 150nm froze above -20 °C. Furthermore, we determined the ice-active site densities normalized to particle concentrations, surface area, and mass of the nanoparticles to show that the samples' nucleation site densities are similar to sea spray aerosols and nanometer-sized dust. The identification and characterization of xylan and laminarin as nanometer-sized ice-nucleating substances expands the growing list of organic matter capable of impacting cloud formation and thus climate.

UV–vis spectroscopy as a rapid method for evaluation of total phenolic hydroxyl structures in lignin

Abstract Phenolic hydroxyl groups in lignin are crucial for understanding its structure, reactivity, and potential applications. Various methods have been developed for the determining phenolic groups in lignin. This study focuses on the comparison of a simple, cost-effective, and time-efficient UV–vis ionization difference technique with the highly accurate 31P NMR spectroscopy for analyzing lignin samples of different origins and isolation methods. The results were carefully evaluated, and the strengths and limitations of each method were discussed. Two eco-friendly UV–vis approaches were proposed for a rapid and comprehensive evaluation of the total phenolic-OH groups: one using a strong alkaline solution for analyzing common types of technical lignins, and another employing multipoint wavelength calculations, effective for analyzing softwood lignins regardless of the extraction method. Additionally, the research highlighted the importance of selecting appropriate model phenolic compounds to accurately assess the phenolic hydroxyl group content in lignins using the UV–vis method. Offering straightforward and rapid analysis, with results closely aligning with 31P NMR data, this method is a promising alternative for routine analysis.

Formation of the emerging disinfection byproducts halocyclopentadienes from phenolic compounds after chlorination

Halocyclopentadienes (HCPDs) are an emerging class of alicyclic disinfection by-products (DBPs) with high toxicity in disinfected drinking water. However, their potential precursors remain unclear, which hinders the understanding of their formation and further development of control strategies. In this study, two HCPDs, 1,2,3,4-tetrachloro-1,3-cyclopentadiene (TCC) and 1,2,3,4,5,5-hexachloro-1,3-cyclopentadiene (HCC), were identified in chlorinated lignin and tannic acid samples for the first time. The chlorination of four lignin-like and two tannic-like phenolic model compounds confirmed that guaiacol and digallic acid can produce HCPDs. According to their structures, ortho-substituents of phenolic compounds were speculated to be crucial for HCPDs formation. The simulated disinfection of catechol, 2-ethoxyphenol (2-EOP), 2-propoxyphenol (2-POP) and 3,4-dihydroxy-5-methoxybenzoic acid (DH-5-MBA) with different ortho-substituents demonstrated that three of these compounds can generate HCPDs, except catechol, which further indicates that ortho-substituents, such as the methoxy, ethoxy and propoxy groups, contribute to HCPDs generation. Guaiacol was the simplest compound for generating HCPDs, and possible formation pathways during chlorination were proposed. Seven hydroxy-chlorocyclopentadienes were tentatively identified and are likely important intermediates of HCPDs formation. Additionally, TCC and HCC were confirmed in tap water and chlorinated SRNOM samples with total concentrations up to 11.07 ng/L and 65.66 ng/L, respectively, further demonstrating the wide existence of HCPDs and their precursors. This study reports the clear precursors of HCPDs and provides a theoretical foundation for controlling HCPDs formation in disinfected drinking water.

Characterization of fused aromatic multirings in lignin via synchronous fluorescence spectroscopy and catalytic hydro-depolymerization

The structural analysis of lignin is highly significant in practical terms. We investigated the presence of fused aromatic multirings (FARs) distinct from conventional phenylpropane units in seven lignin types using synchronous fluorescence spectroscopy (SFS) and quantified their relative proportions. Our findings reveal that FARs are present in all lignin samples, primarily composed of 2–6 rings. The relative distribution of FARs in lignin is ranked as follows: 2 rings > 1 ring > 4 rings > 3 rings > 6 rings > 5 rings. The relative contents of these FARs (1–6 rings) exhibit slight variations across all lignin samples. Notably, FARs with 2 rings are the highest at 35 %−53 %, while those with 5 and 6 rings are the lowest, collectively accounting for less than 1.37 %. Moreover, the relative contents of FARs with 1 and 2–6 rings range approximately 24 %−32 % and 68 %−76 %, respectively. Furthermore, the catalytic hydro-depolymerization of lignin was performed and the experimental results demonstrate that the hydro-liquefied oil from lignin contains aromatic compounds with 1–7 rings, and the relative contents of aromatic compounds with 1 ring and 2–7 rings in the oil are 29 % and 71 %, respectively, which is consistent with that of lignin SFS. These findings are also consistent with the existing literature and experimental results. This study offers an explanation for the low yields observed in current depolymerization processes targeting small molecules within lignin and establishes a theoretical foundation for achieving high yields in the preparation of multiring aromatic hydrocarbons.