Characterization Of Lignin Research Articles

Characterization and Comparison of Some Kraft Lignins Isolated from Different Sources

Lignin characteristics are significantly affected by kraft processing and isolation conditions. In the studies carried out in this context, commercial lignins or isolated lignins from industrial black solutions are generally preferred. In this study, in order to conduct more comprehensive research, three lignin samples were isolated from kraft black liquor obtained from laboratory cooking trials of pine, poplar, and wheat straw chips, representing softwoods, hardwoods, and annual plants, respectively, according to efficient pulping studies. In addition, another lignin-containing industrial waste was provided from a pulp mill (OBL). The acidification method was applied for isolating lignin from black liquor samples. After isolating the lignin samples from different sources, they were characterized and compared with the commercially available kraft lignin sample (Indulin AT). Total phenolic groups, carboxyl groups, purity, functional groups, nitrobenzene oxidation products, molecular weight, thermal stability, and element contents were analyzed. The isolated lignin samples (except wheat straw) were as pure as commercial lignin. Since the wheat straw was agricultural waste and an annual plant, inorganic elements such as P, K, and Si were more abundant than in the other samples. However, the polydispersity and molecular weight of all of the isolated lignin samples were higher than those of commercial lignin. Because the ash contents of the lignin samples for pine, poplar, OBL, and indulin AT were between 1 and 3%, they can be used for high-value applications. In particular, despite some disadvantages, wheat straw lignin has greater potential for use in extruders than softwood lignins due to their syringyl content.

Structural Characterization of the Milled-Wood Lignin Isolated from Sweet Orange Tree (Citrus sinensis) Pruning Residue.

The pruning of sweet orange trees (Citrus sinensis) generates large amounts of lignocellulosic residue. Orange tree pruning (OTP) residue presents a significant lignin content (21.2%). However, there are no previous studies describing the structure of the native lignin in OTPs. In the present work, the "milled-wood lignin" (MWL) was extracted from OTPs and examined in detail via gel permeation chromatography (GPC), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), and two-dimensional nuclear magnetic resonance (2D-NMR). The results indicated that the OTP-MWL was mainly composed of guaiacyl (G) units, followed by syringyl (S) units and minor amounts of p-hydroxyphenyl (H) units (H:G:S composition of 1:62:37). The predominance of G-units had a strong influence on the abundance of the different linkages; therefore, although the most abundant linkages were β-O-4' alkyl-aryl ethers (70% of total lignin linkages), the lignin also contained significant amounts of phenylcoumarans (15%) and resinols (9%), as well as other condensed linkages such as dibenzodioxocins (3%) and spirodienones (3%). The significant content of condensed linkages will make this lignocellulosic residue more recalcitrant to delignification than other hardwoods with lower content of these linkages.

Biphasic lignocellulose fractionation for staged production of cellulose nanofibers and reactive lignin nanospheres: A comparative study on their microstructures and effects as chitosan film reinforcing

The effective fractionation of lignocellulose and the enhancement of its components require formidable efforts. This study explored synergistic biorefinery routes for the holistic conversion of lignocellulose biomass to green nanomaterials through one-pot fractionation using recyclable p-toluenesulfonic acid (p-TsOH)/pentanol reagents. The potential of p-TsOH/pentanol pretreatment of aspen biomass under various temperatures (80–180 °C) for co-production of cellulose nanofibers (CNFs) and lignin nanospheres (LNSs) was investigated. The optimal pretreatment temperature, which minimizes cellulosic degradation and promotes the holistic conversion of biomass, was 120 °C. In addition to its highly digestible nature, the cellulose-rich residue produced high-quality CNFs with a diameter <100 nm, good crystallization, and thermostability, making it suitable for various applications. Lignin characterization, molecular dynamics simulation, and density functional theory analyses of the recovered lignin revealed well-protected β-O-4 bonds (47.3/100 Ar), uniform molecular weights (Mw, 2815 g/mol; Mn, 1704 g/mol; PDI, 1.65), < 1% sugar content, fewer condensed structures, and nanosize shapes (100–300 nm) due to the molecular interactions of p-TsOH and pentanol with lignin units. Moreover, 0.4% LNSs additions reduced the chitosan film thickness by 53% and enhanced its tensile strain and strength by 33 and 59%, respectively, as compared to the pure chitosan film. This study provides a sustainable platform for the co-production of biobased CNFs and LNSs using cutting-edge fractionation of LCB, which is a breakthrough toward industrial biorefineries.

Effect of chemically modified lignin addition on the physicochemical properties of PCL nanofibers

In this study, a chemically modified lignin additive was successfully prepared to improve the physicochemical properties of biodegradable polycaprolactone (PCL)-based nanofibers. The molecular weight and surface functional group characteristics of lignin were effectively controlled through a solvent fractionation process using ethanol. Then, PCL-g-lignin was successfully synthesized by using ethanol-fractionated lignin as a platform for the PCL grafting process. Finally, PCL/PCL-g-lignin composite nanofibers were simply prepared by adding PCL-g-lignin to the PCL doping solution and performing a solution blow spinning process. The addition of PCL-g-lignin could dramatically improve the physical and chemical properties of PCL nanofibers, and in particular, the tensile strength (0.28 MPa) increased by approximately 280 % compared to the conventional PCL. In addition, the lignin moiety present in PCL-g-lignin was able to impart UV blocking properties to PCL nanofibers, and as a result, it was possible to effectively suppress the photolysis phenomenon that occurred rapidly in existing PCL nanofibers. Therefore, PCL-g-lignin may be widely used not only as a reinforcing agent of existing biodegradable nanofibers but also as a functional additive for UV protection.

Newly Synthesized Lignin Microparticles as Bioinspired Oral Drug-Delivery Vehicles: Flavonoid-Carrier Potential and In Vitro Radical-Scavenging Activity.

The aim of the present study was to synthesize lignin microparticles, to evaluate their physicochemical, spectral, morphological and structural characteristics, to examine their encapsulation and in vitro release potential and behaviour towards the flavonoid morin in simulated physiological medium and to assess the in vitro radical-scavenging potential of the morin-loaded lignin microcarrier systems. The physicochemical, structural and morphological characteristics of alkali lignin, lignin particles (LP) and morin-encapsulated lignin microparticles (LMP) were determined based on particle size distribution, SEM, UV/Vis spectrophotometric, FTIR and potentiometric titration analyses. The encapsulation efficiency of LMP was 98.1%. The FTIR analyses proved that morin was successfully encapsulated in the LP without unexpected chemical reactions between the flavonoid and the heteropolymer. The in vitro release performance of the microcarrier system was successfully mathematically described by Korsmeyer-Peppas and the sigmoidal models outlining the general role of diffusion during the initial stages of the in vitro release process in simulated gastric fluid (SGF), and the predominant contribution of biopolymer relaxation and erosion was determined in simulated intestinal medium (SIF). The higher radical-scavenging potential of LMP, as compared to that of LP, was proven via DPPH and ABTS assays. The synthesis of lignin microcarriers not only provides a facile approach for the utilization of the heteropolymer but also determines its potential for the design of drug-delivery matrices.

Mild isolation and characterization of surface lignin from hydrothermally pretreated lignocellulosic forestry and agro-industrial waste biomass

Within the biorefining concept, the lignocellulosic biomass wastes can serve as feedstock to produce value-added chemicals and fuels. The sustainable valorization of biomass is based on integrated processes that aim to the utilization of “whole biomass”. To this end, the first step of the efficient biomass pretreatment towards selective isolation of cellulose, hemicellulose and lignin, is of paramount importance. Hydrothermal pretreatment of biomass in neat water is a green and well-established process that enhances hemicellulose removal and recovery in the liquid fraction, affording a cellulose and lignin enriched solid which can be enzymatically hydrolyzed to glucose. A simple and efficient method to facilitate the hydrolysis is the prior extraction of the formed “surface” lignin which hinders the action of enzymes. Within this context, in this work, forestry (beechwood sawdust) and agro-industrial (vine prunings, apricot kernel shells) wastes were hydrothermally pretreated in neat water (at 220 °C, 15 min) and the formed surface lignin was extracted via soxhlet or reflux methods under mild conditions, with the use of green solvents (ethanol, acetone). The delignification degree of the pretreated biomass was in the range of 35–67 wt%, depending on the solvent and biomass feedstock. The recovered surface lignins were of high purity and exhibited similar physicochemical and structural characteristics with the organosolv lignin. The fast pyrolysis of surface lignins afforded bio-oils enriched in alkoxy-phenols and oxy-aromatics. The biomass solids recovered after lignin extraction are enriched in cellulose (70%) and exhibit high relative crystallinity and improved textural properties, thus increasing their potential valorization.

Characterisation of lignins isolated from Bamboo organosolv and kraft black liquor

Bamboo biomass was pulped using organosolv methods: Acetic acid and formic acid; hydrogen peroxide and formic acid; ethanol and water and kraft process with varying concentrations of the cooking chemicals. The properties of the isolated lignin were influenced by the black liquor pH as well as the pulping method. Highest pH (12,8) was recorded for kraft at 70:30 liquor concentration while lowest pH of 2,5 was recorded for both Aceticformic (70:30) and Ethanol/water (70:30 and 60:40). There were obvious differences in the characteristic colours, shapes and sizes of the lignin samples. Bamboo kraft lignin samples formed large pieces much easier than that of Organosolv. Aceticformic (70:30) had the best filteration properties (FC) while Ethanol/water had the poorest. Generally, kraft recorded the highest lignin yield while all the organosolv processes recorded reduced yield. Highest yield (119,25 g/L) was gotten from kraft (50:50) while Peroxyformic (60:40) had the lowest yield of 8,20 g/L. The results showed that higher liquor pH favours total dissolved solid as well as lignin precipitation. As the pH increases, total dissolved solid, yield, Klason and low molecular weight (LMW) lignin content increases while FC decreases. The Klason and LMW lignin content increased with incresing lignin yield.

Insight into the structural feature, ash transformation behavior, and alkali metal heat release characteristic of industrial lignin via experimental and equilibrium evaluation

The release characteristics of inorganic minerals during the thermochemical transformation of organic solid wastes are one of the key issues for their resource utilization. This study concentrated on the chemical structure of three kinds of industrial lignin and the release pattern and mechanism of alkali metal elements during heat treatment by means of 13C NMR, FTIR, XRD, SEM, and chemical thermodynamic equilibrium simulation. The microstructures of the three lignin samples were studied using 13C NMR and FTIR. The three lignin samples contained much more aliphatic and aromatic carbon than carbonyl carbon, and the aliphatic carbon moieties contained the most oxygenated carbon. The lignin samples mainly had aromatic molecular structures with aromaticity (fa) of 55.76% (sodium lignin sulfonate, SL), 52.62% (calcium lignin sulfonate, CL), and 63.93% (de-alkalized lignin, DL), respectively. Carbonyl content in DL was lower than lignin sulfonate SL and CL. The benzene ring content of SL was lower than the other two lignin samples. Na+ metal salts promoted the pyrolysis of lignin samples, while Ca2+ metal salts inhibited the pyrolysis of lignin samples. Microstructural studies showed that the structure of SL evolved from columnar and granular coexistence breaking into filamentous protrusions and lamellar structures with the increase of pyrolysis temperature. The CL and DL samples became ash presented in granular state and the particle size continued to become smaller with increasing temperature as the distribution gap became larger. The chemical thermodynamic equilibrium calculations showed that the variation in the initial concentrations of Na+ and Ca2+ in the three lignin samples led to different release characteristics of the three lignin samples. Na+ release rate was higher than that of Ca2+, and the valence state of the metal ions was an important reason for this phenomenon. This study provides data support and theoretical basis for the migration and release pattern of alkali metal during the thermal conversion reaction of organic solid waste applications.

Technical kraft lignin from coffee parchment

Abstract The biomass deconstructed by kraft process and the lignin dissolved in the black liquor are burned to generate energy in a pulp mill. This study used the black liquor from coffee parchment cooking, a residue from the coffee industry, to isolate kraft technical lignin. The parchment was subjected to the kraft pulping process to obtain pulps of kappa number 60 and 25, and the resulting black liquors were used for lignin extraction. Chemical characterization, elemental analysis and heating value of liquors and lignins were performed, as well as FTIR and Py-CG-MS analysis of lignins. The cooking provided liquors with similar characteristics, with lignin content of 31.67 and 32.63% for kappa 60 and 25 liquors, respectively. The extractions resulted in high purity lignin (92.35% for K#60 lignin and 93.96% for K#25 lignin). The higher heating values were 23.8 and 25.4 MJ/kg for K#25 and K#60 lignins, respectively. FTIR analysis showed characteristic peaks of lignin. Through Py-GC-MS, it was possible to observe the slight predominance of guaiacyl-type lignin, which can be an advantage depending on the application. It is possible to extract lignin from the black liquor obtained from the coffee parchment pulping to generate products with high-added value.

Elucidating the effect of the physicochemical properties of organosolv lignins on its solubility and reductive catalytic depolymerization

Unsatisfactory solubility and recalcitrant condensed structures of isolated lignins (technical lignins) severely limit their processability into renewable materials, fuels, and chemicals. Therefore, a comprehensive understanding of the structural and physicochemical properties of isolated lignins is of great value in explaining their performance in the solubilization and further depolymerization to high-value applications. In this work, we investigated the solubilization and depolymerization performance of organosolv lignins from three different sources (beech (L01), birch (L02), and wheat straw (L03)). We applied sequential solvent fractionation as a tool to subdivide parent lignins into four more homogeneous subfractions (SF1, SF2, SF3, and IF), with a gradual increase in molecular weight and interunit linkages and a decrease in phenolic –OH group from SF1 to IF. The solubility tests of the parent lignins and their subfractions at ambient conditions were carried out in six organic solvents (n-hexane, diisopropyl ether, ethyl acetate, ethanol, methanol, and acetone) with large differences in Hansen solubility parameters. Among the solvents studied, the solvents with δp > 8 MPa1/2 demonstrated a high solubilization yield of organosolv parent lignins and their subfractions. The solubilization behavior of parent lignins and subfractions was further described based on their inherent structural properties, such as molecular weight and functional group content (phenolic –OH and –COOH). The structure–reactivity characteristics of parent organosolv lignin and their subfractions were also investigated under different conditions in the presence of catalyst-containing transition (NiHTC-500) and noble (Pd/C) metals as active centers. Strong structural correlations between parent lignin/subfractions and depolymerized lignin oils were derived using GC-FID/MS, GPC, 1H–13C HSQC NMR, and 31P NMR.

Lignin structural elucidation and compositions investigation of Camellia oleifera fruits collected from various locations

A sufficient understanding of structural characteristics of lignin is essential for the production of biomaterials, bioenergy, and biochemicals from lignocellulosic biomass. Camellia oleifera fruit shell (CFS) is a considerable waste lignocellulosic resource in the camellia seed oil production industry, and contains a large amount lignin. Herein, to understand the structural characteristics of CFS lignin, double enzymatic lignins (DEL) and acid-soluble lignins (ASL) from CFS collected from various locations were separated and thoroughly characterized. Additionally, to synthetically comprehend the difference among the six camellia varieties, the chemical compositions of the camellia fruits were also studied. The results showed that the ASL from XL210 shells showed the highest lignin derivative content (4.15 wt %). All DEL were of the SG-type with low S/G ratios (0.47–0.88) and homogeneous structures (Mw/Mn, 2.00–2.06). The DEL showed a high content of β−O−4 aryl ether linkages (41.89–48.26/100 Ar) and C−C interunit linkages, namely β−β (14.84–26.30/100 Ar) and β−5 (9.61–13.85/100 Ar). DELQD had the highest total phenolic OH content (2.64 mmol/g) among the six DEL. Finally, the structural models of the DEL were depicted. Understanding the chemical compositions of Camellia oleifera fruits and structural characteristics of the CFS lignins would facilitate the optimization of the pretreatment process and the deconstruction of the CFS, and in addition, it would be important for the future comprehensive utilization of Camellia oleifera fruits and the valorization of the CFS.

Biodegradation characteristics of lignin in pulping wastewater by the thermophilic Serratia sp. AXJ-M: Performance, genetic background, metabolic pathway and toxicity assessment

The key to the efficient removal of pulping wastewater lies in the effective degradation of lignin at high temperature. There is thus an urgent need to seek effective eco-environmental techniques to overcome this environmental limit for lignin degradation. The soil isolate thermophilic Serratia sp. AXJ-M efficiently metabolizes lignin. Nevertheless, the underlying comprehensive molecular mechanism of lignin degradation by thermophilic AXJ-M is poorly understood. Here, strain AXJ-M showed excellent degradation ability toward diverse lignin-related aromatic compounds. Functional genome analysis and RNA-Seq disclosed several traits which in joint consideration suggest a high efficiency of AXJ-M representative to the lignin degradation and environmental adaptation. Multiomics analyses combined with GC–MS revealed seven potential lignin biodegradation pathways. DyP was predicted to be involved in the breakdown of the β-O-4 ether bond, Cα-Cβ bond and Cα oxidation of lignin by prokaryotic expression and gene knockout and complementation. Molecular docking deepens the understanding of the interaction between DyP and lignin. Toxicity assessment experiments clearly indicated that AXJ-M significantly reduced the toxicity of the metabolites. This work expands the knowledge about the degradation mechanism of thermophilic lignin-degrading bacteria, most importantly, offers a new perspective on potential applications in utilizing this strain in pulping wastewater bioremediation.

Lignin-based epoxy composite vitrimers with light-controlled remoldability

Vitrimers open new possibilities in the reprocess of epoxy and other thermosets. However, direct heating is not practical on many occasions, and the waste vitrimers would cause great harm to the environment. In this work, we propose to use kraft lignin (KL) to fabricate vitrimer with reprocessability and environmental friendliness. The lignin-based epoxy vitrimer was fabricated by blending epoxy-modified KL and poly(ethylene glycol) bis(carboxymethyl) ether (PEG-DCM). The obtained lignin-based epoxy vitrimer (EML/PEG-DCM) showed good light-to-heat capability. Under the infrared radiation (808 nm, 1 W cm−2) for only 30 s, the surface temperature of EML/PEG-DCM was over ∼148 °C, and reached the maximum at ∼231 °C for 5 min. This good light-to-heat effect can activate the dynamic 3D cross-linking networks and repair the vitrimer. The energy consumption of the light-controlled remolding process is only one-thousandth of the conventional hot-press. This study not only helps to explore the natural characteristics of lignins, promoting their functional and intelligent utilization, but also provides a new raw material platform for the development of green vitrimer materials.

Structural conversion and characterization of Camellia oleifera shell lignin based on mechanochemical-assisted pretreatment

Camellia oleifera shells (COS), are the by-product of Camellia oleifera seed oil processing, and possess a high lignin content (38.6%). However, information on the fundamental chemistry of this lignin is limited. Herein, mechanochemical strategies combining ball-milling with mild acetosolv or alkaline treatment are presented to compare the structural evolution of COS lignins. The mechanochemical processes significantly improve the lignin yield, releasing lignins with high molecular weights (Mw ≈ 7000 mol/g). The COS lignins are GS-type lignins, and G units account for 71.9% of MWL. The synergistic combination of ball-milling and acetosolv treatment led to the cleavage of β-O-4 linkages. In contrast, the alkaline lignin fractions retained a large number of β-O-4 linkages (50.67/100 Ar) and a low phenolic OH content (1.56 mmol/g), indicating that the ball-milling process had little effect on the alkaline lignin structures (typical substructures). In summary, understanding the structural conversion and characteristics of lignins during the combined pretreatments of COS would facilitate the optimization of the pretreatment process and the deconstruction of COS.

Revealing adsorption of mixed enzymes onto lignin resulted from integration of hydrothermal and chemi-mechanical pretreatment

Lignin is the main factor inhibiting enzymatic hydrolysis of lignocellulosic biomass. Different pretreatments can alter chemical and structural characteristics of lignin, thus affecting its adsorption capacity of enzymes. Herein, enzymatic mild acid lignin (EMAL) was separated from poplar branch wood chips as substrates resulted from different combined pretreatments, and then characterized and adsorbed by enzymes, so as to study the effects of different pretreatments on enzyme adsorption capacity. The results showed that the phenolic hydroxyl content and CC bond number of lignin increased after hydrothermal pretreatment, which increased the unproductive adsorption of mixed enzymes through hydrophobic interaction and hydrogen bonds. Chemical pretreatment after hydrothermal pretreatment can further reduce the unproductive adsorption of lignin on mixed enzymes, improving the enzymatic hydrolysis of substrates. This study would help to unmask the adsorption of mixed enzymes on lignin resulted from combined pretreatments, and facilitate the rapid development of efficient pretreatment for lignocellulosic biomass.

Enzyme-Catalyzed Polymerization of Kraft Lignin from Eucalyptus globulus: Comparison of Bacterial and Fungal Laccases Efficacy.

Kraft lignin, a side-stream from the pulp and paper industry, can be modified by laccases for the synthesis of high added-value products. This work aims to study different laccase sources, including a bacterial laccase from Streptomyces ipomoeae (SiLA) and a fungal laccase from Myceliophthora thermophila (MtL), for kraft lignin polymerization. To study the influence of some variables in these processes, a central composite design (CCD) with two continuous variables (enzyme concentration and reaction time) and three levels for each variable was used. The prediction of the behavior of the output variables (phenolic content and molecular weight of lignins) were modelled by means of response surface methodology (RSM). Moreover, characterization of lignins was performed by Fourier-transform infrared (FTIR) spectroscopy and different nuclear magnetic resonance (NMR) spectroscopy techniques. In addition, antioxidant activity was also analyzed. Results showed that lignin polymerization (referring to polymerization as lower phenolic content and higher molecular weight) occurred by the action of both laccases. The enzyme concentration was the most influential variable in the lignin polymerization reaction within the range studied for SiLA laccase, while the most influential variable for MtL laccase was the reaction time. FTIR and NMR characterization analysis corroborated lignin polymerization results obtained from the RSM.

Esterification of lignin with long chain fatty acids for the stabilization of oil-in-water Pickering emulsions

Pickering emulsions offer numerous advantages over conventional surfactant-stabilized emulsion systems, including lower loading levels and enhanced long-term stability. Through both organic and inorganic Pickering emulsifying particles exist, more efforts are being invested in devising renewable, biodegradable, and non-toxic alternatives to conventional Pickering emulsifiers. In this study, the use of lignin (unmodified and esterified) specimens as an effective alternative to conventional Pickering emulsifiers was investigated. Hexanoyl chloride, decanoyl chloride, and palmitoyl chloride esterified lignin specimens were produced and their employability as Pickering emulsifiers was studied. The effects of varying the concentrations of lignin (unmodified and esterified specimens) and pH of the dispersion medium on the stability of the produced Pickering emulsions were explored. Comprehensive characterization of the esterified lignin stabilized Pickering emulsions exhibited enhanced stability, and smaller average oil droplet size, resulting in stable Pickering emulsions with high zeta potential and better flow properties. Overall, the studied esterified lignin specimens can have appealing applications in various Pickering emulsion systems, as a nontoxic and sustainable alternative to conventional emulsifiers.

Fractionation of lignin from rice straw using an acidified biphasic solvent system

To obtain lignin from lignocellulosic biomass, phenoxyethanol (EPH) was employed to construct a biphasic solvent system. The concentration of EPH in this biphasic solvent system was first studied to determine a pretreatment condition for fractionation of lignin. Then, the fractionation of lignin from rice straw was performed under the conditions of temperature 130 °C, cooking time 60 min and sulfuric acid concentration 0.1 M, in 70 % aqueous EPH solvent system. The results showed that 50.97 %, 49.52 % or 82.02 % of the removed lignin with the purity of 89.04 %, 91.30 % or 84.76 % was regenerated from EPH liquor using dimethyl carbonate (DMC), dimethoxymethane (DMM) or diethyl ether (DE) as precipitant, respectively. Additionally, the weight-average molecular weight (Mw) and dispersity index (Đ) of the regenerated lignin decreased to 4247–4809 g/mol and 1.26–1.60 compared with that of the original lignin (5654 g/mol and 4.78). Finally, the compositional and structural characteristics of lignin, e.g., molecular weight and molecular structure, were also investigated by DSC, HSQC and elemental analysis.

Sustainable lignocellulose fractionation by integrating p-toluenesulfonic acid/pentanol pretreatment with mannitol for efficient production of glucose, native-like lignin, and furfural

A new cutting-edge lignocellulose fractionation technology for the co-production of glucose, native-like lignin, and furfural was introduced using mannitol (MT)-assisted p-toluenesulfonic acid/pentanol pretreatment, as an eco-friendly process. The addition of optimized 5% MT in pretreatment enhanced the delignification rate by 29% and enlarged the surface area and biomass porosity by 1.07–1.80 folds. This increased the glucose yield by 45% (from 65.34 to 94.54%) after enzymatic hydrolysis relative to those without MT. The extracted lignin in the organic phase of pretreatment exhibited β-O-4 bonds (61.54/100 Ar) properties of native cellulosic enzyme lignin. Lignin characterization and molecular docking analyses revealed that the hydroxyl tails of MT were incorporated with lignin and formed etherified lignin, which preserved high lignin integrity. The solubilized hemicellulose (96%) in the liquid phase of pretreatment was converted into furfural with a yield of 83.99%. The MT-assisted pretreatment could contribute to a waste-free biorefinery pathway toward a circular bioeconomy.

Effects of Fe addition on pyrolysis characteristics of lignin, cellulose and hemicellulose

In this paper, the pyrolyzed influence of Fe contents (0%, 1% and 5%) on the lignin, cellulose and hemicellulose were carried out by thermogravimetric and Fourier transform infrared spectroscopy. The pyrolysis process, kinetic characteristics and release characteristics of the pyrolysis products on the three major components were studied. The results showed that the addition of Fe increases the yield of cellulose biochar. The yield of lignin and hemicellulose biochar are also related to the addition of Fe. The kinetic analysis showed that Fe supplementation significantly decreases the activation energy of lignin, but increases the activation energy of cellulose, while the activation energy of hemicellulose was closely related to Fe addition (149.95 kJ/mol under 1% Fe and 127.84 kJ/mol under 5% Fe). The release characteristics of the pyrolysis products showed that the observed pyrolysis products mainly included H2O, CH4, CO2 and CO. An addition of 5% Fe increased CH4, CO and CO2 production in the pyrolysis process of the three components and produced less H2O.