Pure Lignin Research Articles

Efficient separation of functional xylooligosaccharide, cellulose and lignin from poplar via thermal acetic acid/sodium acetate hydrolysis and subsequent kraft pulping

Thermal acetic acid/sodium acetate hydrolysis (ASH) on poplar wood chips were carried out to obtain functional xylooligosaccharide, then the hydrolyzed wood chips were subjected to kraft pulping (KP) to fractionate cellulose and lignin. The separated three fractions were extensively characterized for further utilization in view of the integral biorefinery concept. The extraction efficiency of hemicelluloses by ASH strongly depends on the buffer ratio of the acetic acid/sodium acetate buffer solution. The ASH facilitated producing a high ratio of xylooligosaccharides with high molecular weight, while prevented further degradation of the saccharides, and simultaneously inhibited the condensation of lignin facilitating the subsequent kraft delignification. The obtained cellulose pulps had higher intrinsic viscosities as compared with the traditional autohydrolysis-KP process. Moreover, the ASH-KP process delivered a high purity of lignin with relatively high molecular weight. Therefore, the proposed integrated fractionation strategy is conducive to convert the lignocellulosic components into bio-based functional materials.

Recovery of High Purity Lignin and Digestible Cellulose from Oil Palm Empty Fruit Bunch Using Low Acid-Catalyzed Organosolv Pretreatment

The lignocellulosic residue from the palm oil industry, oil palm empty fruit bunch (OPEFB), represents a challenge to both producing industries and environment due to its disposal difficulties. Alternatively, OPEFB can be used for the production of valuable products if pretreatment methods, which overcome OPEFB recalcitrance and allow tailored valorization of all its carbohydrates and lignin, are developed. Specifically, high-value applications for lignin, to increase its contribution to the feasibility of lignocellulosic biorefineries, demand high-purity fractions. In this study, acid-catalyzed organosolv using ethanol as a solvent was used for the recovery of high-purity lignin and digestible cellulose. Factors including catalyst type and its concentration, temperature, retention time, and solid-to-liquid (S/L) ratio were found to influence lignin purity and recovery. At the best conditions (0.07% H2SO4, 210 °C, 90 min, and S/L ratio of 1:10), a lignin purity and recovery of 70.6 ± 4.9% and 64.94 ± 1.09%, respectively, were obtained in addition to the glucan-rich fraction. The glucan-rich fraction showed 94.06 ± 4.71% digestibility within 18 h at an enzyme loading of 30 filter paper units (FPU) /g glucan. Therefore, ethanol organosolv can be used for fractionating OPEFB into three high-quality fractions (glucan, lignin, and hemicellulosic compounds) for further tailored biorefining using low acid concentrations. Especially, the use of ethanol opens the possibility for integration of 1st and 2nd generation ethanol benefiting from the separation of high-purity lignin.

Fractionation and characterization of lignins from Miscanthus via organosolv and soda pulping for biorefinery applications

The structural complexity of lignins necessitates characterization and isolation methodologies for assessing their appropriateness for thermo-chemical systems and material applications. Lignins prepared via two pulping methods (organosolv and soda) were comprehensively investigated by analyzing the properties, including lignin purity, yield, and thermal and chemical properties. The extracted organosolv lignin has high purity (93.13–98.12%), however, the purity of soda lignin was relatively low (87.58–89.61%). Organosolv lignin produced the highest heating value of 26.79–26.95 MJ kg−1, with a fixed carbon content of 39.47–41.06 wt%, high purity, and low ash content, making it suitable for biofuel applications. The content of total phenolic OH groups was higher for the organosolv lignins; however, for the phenolic OH groups, the 4-vinylphenol content was significantly higher in the soda lignins, and increased with increasing NaOH concentration. Overall, the thermal and chemical properties related to the lignin structure changed with the fractionation method and solvent concentration, which in turn influences the design of lignin valorization strategies for prospective depolymerization and material applications.

Purity and structural composition of lignin isolated from Miscanthus x giganteus by sub-critical water extraction with associated modifiers

Lignin is an industrial by-product produced from the pulping and paper industry, where the process generates lignin in the form of lignosulphonates. While there are many applications for lignin, there are all low value and attempts to add value to lignin are hindered by its complex physicochemical nature and the presence of sulphur. Adopting the biorefining concept, the study evaluates the impact of direct (DE) and sequential extraction (SE) of Miscanthus x giganteus using sub-critical water with associated modifiers; ethanol and carbon dioxide on the physical and chemical properties of the extracted lignin. Isolated lignins were characterised by a Fourier Transform Infrared Spectroscopy (FTIR). Although higher delignification was achieved by DE and SE about 81.5% and 58.0%, respectively, the lignin recovered from the SE process showed remarkably higher purity with 91.5%. Lignin recovery did not differ considerably for either processing method. FTIR revealed a qualitative reduction in the intensity of bonds corresponding to hydroxyl groups for the lignin derived from DE rather than SE processing routes. These indicated that the lignin derived from SE had potential for subsequent preparation in lignin value-added bio-based materials.

Carbon fibers derived from pure alkali lignin fibers through electrospinning with carbonization

Alkali lignin (AL) fibers with a smooth surface and fine morphological appearance were successfully produced via electrospinning using a simple heated single spinneret system, instead of typical electrospinning of lignin with added synthetic polymer blends or conventional co-axial electrospinning. To reduce the size of the fibers, glycerol was added to the spinning solution as a co-solvent for surface tension reduction and electrospinnability improvement. After electrospinning, stabilization and carbonization were subsequently performed to convert AL fibers to carbon fibers (CFs). The obtained CFs displayed rough and uneven surfaces. However, the CFs derived from glycerol-added solution showed greater electrical conductivity, specific surface area, and porosity compared with those from pure AL solution. Furthermore, the results indicated that the inorganic salts on the rough surface of CFs were successfully removed by sulfuric acid (H2SO4) washing. After H2SO4 washing, the CFs revealed a smoother surface and higher electrical conductivity, specific surface area, and porosity.

Synergistic effect of humic acid on alkali pretreatment of sugarcane bagasse for the recovery of lignin with phenomenal properties

Lignin forms a recalcitrant structure in lignocellulosic biomass and hence huge amount of enzymes are required for disintegrating it into their subsequent components, like glucose and other by-products. Thus, the pretreatment is an ineluctable step in the bioethanol scheme for the delignification of biomass and also the recovery of lignin, an emerging value added polymer in many industrial applications. A green facile method was developed wherein humic acid (HA) acts as a catalyst and surfactant in the alkali pretreatment of sugarcane bagasse for the step reduction in lignin recovery scheme with phenomenal properties and enhanced enzymatic-hydrolysis. HA assisted experiments were performed with and without calcium chloride (CaCl2). Effective disintegration of lignocellulose by the cleavage of β-O-4 moieties resulted in forming lignin and hydrolyzable biomaterial via two pathways. Possible covalent linkages between the HA and lignin resulted in the release of esters as a byproduct. Thus, the delignified biomass, the isolated lignin and a variety of esters, could be valorised in various industrial applications. The biomass was characterized by XRD and SEM analysis. The isolated lignin was characterized using FTIR, NMR, GPC, SEM, and TGA – DTA studies. The yield of recovered pure lignin for the two process was 90–100%, as measured through gravimetric analysis. The produced esters were confirmed using FTIR studies. Batch enzymatic hydrolysis was performed for the HA assisted de-lignified bagasse (without CaCl2), which demonstrated a 19% increase in glucose yield compared to the alkali treated bagasse. The produced hydrolysates were subjected to fermentation for the production of ethanol.

Biphasic fractionation of rice straw under mild condition in acidified 2-phenoxyethanol/water system

A novel biphasic organic solvent, 2-phenoxyethanol (EPH) was introduced to pretreat and fractionate rice straw into glucose/glucan, xylose/xylan and lignin under mild conditions. In addition, the combined severity factor (CSF) was used to evaluate the effect of pretreatment severity on the composition variation of rice straw. Under the biphasic system (0.05 M H2SO4, 70 % EPH:30 % H2O), 130 ℃ cooking rice straw 2 h, 86.48 % of cellulose retention in solid residue, 92.10 % of hemicellulose removal and 63.16 % of lignin removal were obtained. Then, the solid residue was enzymatically digested with a glucose yield of 80.94 % at 36 h, and the pure lignin (92.60 %) was recovered by simple precipitation. Based on the fractionation process, 96.69 % of glucose and glucan, 81.83 % of xylose and xylan, and 71.71 % of lignin in solid and liquid phase were recovered. Finally, the residue, especially the retrieved lignin was characterized by SEM, XRD, FTIR, HSQC and thermogravimetric analysis.

Pure, stable and highly antioxidant lignin nanoparticles from elephant grass

Finding renewable and green resources for nanomaterial preparation is a compelling topic concerning the sustainability in nanotechnological applications. In particular, lignin-based nanoparticles are pivotal for unlocking the use of lignin in value added products. In this paper, we isolated pure lignin (ca. 98 % of purity) from elephant grass (Pennisetum purpureum) using two simple extractions with diluted acid and alkali solutions and prepared lignin and lignin acetate nanoparticles dispersed in water-basis by anti-solvent addition. Elephant grass in natura contains ca. 25 % of lignin, which could be converted into lignin nanoparticles with a 37 % yield. Spherical lignin and lignin acetate nanoparticles were revealed by electron microscopies (TEM and FESEM) and proved to be stable in a wide pH range (5–11) and ionic strength lower than 0.01. Lignin nanoparticles showed higher antioxidant activity (RSI of ca. 82) as compared to lignin in solution and to the commercial antioxidants (BHT and BHA). These nanoparticles were successfully incorporated in a neutral cream, resulting in a tinted sunscreen formulation with both ultraviolet and visible absorption. Altogether, we present here an effective method to isolate pure lignin from a non-food biomass and to prepare stable and highly antioxidant lignin nanoparticles that can be applied in dermocosmetics and are intrinsically non-toxic to the environment.

Extraction Behaviors of Lignin and Hemicellulose-Derived Sugars During Organosolv Fractionation of Agricultural Residues Using a Bench-Scale Ball Milling Reactor

Ethanol organosolv fractionation combined with ball milling was conducted on three major agricultural residues: Rice husk (RH), rice straw (RS), and barley straw (BS). The highest lignin extraction yields of RH, RS, and BS were 55.2%, 53.1%, and 59.4% and the purity of lignin recovered was 99.5% for RH and RS, and 96.8% for BS, with similar chemical characteristics, i.e., low molecular weight distributions (1453–1817 g/mol) and poly dispersity index (1.15–1.28). However, considering the simultaneous production of hemicellulose-derived sugars, distinctive fractionation behaviors were shown for the three agricultural residues. The highest hemicellulose-derived sugar yield was 73.8% when RH was fractionated at 170 °C for 30 min. Meanwhile, very low sugar yields of 31.9% and 35.7% were obtained from RS and BS, respectively. The highest glucan-to-glucose conversion yield from enzymatic hydrolysis of fractionated RH reached 85.2%. Meanwhile, the enzymatic digestibility of the fractionated RS and BS was 60.0% and 70.5%, respectively. Consequently, the fractionation efficiency for RH can be improved with fine refinement. For the case of RS, other fractionation process should be applied to achieve effective fractionation performance.

Comparison study of lignin-kraft extraction process from black liquor using centrifuge and thermal acid hydrolysis methods

Black liquor is a remnant of pulping fluid which generally consists of 14-18 percent solids which is commonly known as weak black liquor (WBL) with a pH of 12 or more. About 65 percent of the solids contained in black liquor are organic compounds derived from wood such as lignin, resins and fatty acids, acids from carbohydrates, and other organic compounds; The remaining 35percent percent is white liquor which is used in the pulping process. Kraft lignin, also called sulfate or alkali lignin, is obtained from black liquor by the extraction method using an acid hydrolysis process, so that pure kraft lignin compounds can be obtained which can be further utilized in various industrial activities. This study is comparing two kraft lignin extraction methods of acid hydrolysis process with thermal assistance (heating temperature) and a gradual centrifuge. The experiment results showed that the levels of lignin contained in black liquor consist of total calories of 391 kcal / Kg which can be processed into energy sources in the recovery boiler unit in further process. The result of kraft lignin extraction process using the acid hydrolysis method with gradual centrifuge stage is better than the thermal acid hydrolysis method. Quantitatively calculated with ASL values difference of around 0.002 mg / g of both the method and the AIR Value using centrifuge give an average yield of 969.815 mg / g, while using thermal assistance gives an average yield of 679.790 mg / g. Qualitatively, the centrifuge method is more optimal compared to the thermal method shown by the results of ICP, FTIR and SEM testing.

The Effect of Acid Concentration (H2SO4) on the Yield and Functional Group during Lignin Isolation of Biomass Waste Pulp and Paper Industry

Declining oil production in Indonesia lately has been much discussed by industrial practitioners, especially from the petroleum industry. The decrease is due to the age of old drilling wells with high water cut (> 90%), so it is necessary to pursue a production method that can increase the production of these old wells. The EOR (Enhanced Oil Recovery) method is one way of extracting oil from oil wells that cannot be further retrieved by injecting materials that are not in the reservoir. One ingredient that can be injected is Sodium Ligno Sulfonate (SLS) surfactant derived from lignin. Lignin was obtained from the lignin isolation process from Black Liquor, which in this study came from the pulp and paper mill waste of PT. Indah Kiat, Pekanbaru, Sumatra, Indonesia. This study aims to determine the effect of variations in H2SO4 concentrations (concentrations of 15%, 20%, 25%, 30% w/w) on the yield of lignin isolation results, and to compare the functional groups between dirty lignin, clean lignin, and pure lignin using FT-IR. Based on the research results, it was found that the best lignin is lignin with an H2SO4 concentration of 20%, with the highest yield and the color of lignin produced tends to be similar to pure lignin. In addition, it was found that the peak of the net lignin group had more similarity with commercial lignin compared to crude lignin. Keywords: Lignin, Black Liquor, Enhanced Oil Recovery (EOR), FTIR

Utilization of Trapa natans

In this study, Trapa natans nut collected from the costs of Inkumu-Bartin was analyzed according to its lignin content. Acid-insoluble lignin content was determined according to TAPPI T222om-02 as 28.31%. TGA and FTIR analyses were performed. FTIR analysis indicated that Trapa natans contained cellulose, hemicelluloses and lignin. The peaks at 1506-1510 cm-1 in both samples are characteristic peaks for the lignin components due to C = O and COO-non-symmetric stretching vibrations in the aromatic rings of the lignin structure. 1510 cm-s peak is found in the literature as lignin’s fingerprint peak. The peaks at 1230-1270 cm-1 band show the vibrations of guayasil ring with CO tension in lignin and hemicelluloses. Around the peaks of 900, 1025, 1030 and 1050 cm-1 bands cellulose’s O-H, C-H and C-O-C type bonds are seen. When TGA analyzes are examined, approximately 4.5% of the sample is lost from 30 °C to 200 °C. At these intervals, samples generally lose volatile constituents and moisture. From 200 to 271 °C 4.6% of the weight is lost. The decrease in this range may be due to the decomposition of cellulose and hemicelluloses. The DTG curve shows maxima weight-loss occurring at 349 °C. The weight-loss in the range from 271-352 °C is about 50%. Pure lignin sample’s TGA and DTG curve results show 10%, 50%, and 70% weight-losses at 233 °C, 489 °C, and 1167 °C respectively. According to these results, dominantly lignin and small quantities of cellulose and hemicelluloses are present in trapa samples.

Cost-effective production of organosolv lignin from woody biomass using ethanol-water mixed solvent at mild conditions

A cost-effective process has been developed for fractionating pine sawdust into lignin and cellulose fractions in an ethanol-water mixed solvent. The effects of temperature, different types of catalysts (i.e., strong acid, weak acid and alkali), and residence time, with respect to yields and purity of the crude lignin (degraded products) and crude cellulose (solid residue) were investigated. It is found that the purity of crude lignin was higher but with a lower product yield under a weak acid or alkali catalysis in comparison to strong acid treatments. According to the analysis results, the optimal conditions for fractionation process were as follows: a mixed solvent of ethanol-water (1:1, v/v), 15 % formic acid (based on dry biomass), 180 °C, and 60 min. The yield of the resulted crude lignin was 29.2 % with a purity of 54.6 %, and yield of crude cellulose was 64.6 % with a high purity of 84.3 %.

Effect of Lignin Modification on Properties of Kenaf Core Fiber Reinforced Poly(Butylene Succinate) Biocomposites.

In this study, the effects of lignin modification on the properties of kenaf core fiber reinforced poly(butylene succinate) biocomposites were examined. A weight percent gain (WPG) value of 30.21% was recorded after the lignin were modified with maleic anhydride. Lower mechanical properties were observed for lignin composites because of incompatible bonding between the hydrophobic matrix and the hydrophilic lignin. Modified lignin (ML) was found to have a better interfacial bonding, since maleic anhydrides remove most of the hydrophilic hydrogen bonding (this was proven by a Fourier-transform infrared (FTIR) spectrometer—a reduction of broadband near 3400 cm−1, corresponding to the –OH stretching vibration of hydroxyl groups for the ML samples). On the other hand, ML was found to have a slightly lower glass transition temperature, Tg, since reactions with maleic anhydride destroy most of the intra- and inter-molecular hydrogen bonds, resulting in a softer structure at elevated temperatures. The addition of kraft lignin was found to increase the thermal stability of the PBS polymer composites, while modified kraft lignin showed higher thermal stability than pure kraft lignin and possessed delayed onset thermal degradation temperature.

Bio-FLASHCHAIN® theory for rapid devolatilization of biomass 1. Lignin devolatilization

This study validates a modeling framework to accurately predict the total and tar yields from any lignin at any devolatilization conditions. The original reaction mechanism and depolymerization kinetics in bio-FLASHCHAIN® are slightly modified for pure lignin, and used to accurately interpret how the molecular weight distribution (MWD) of a lignin governs its primary devolatilization behavior. The only sample-specific input requirements are an ultimate analysis and a weight-average molecular weight (MW), although a measured MW-value is not needed for lignin in whole biomass. Predicted total and tar yields are validated with measured values from 20 diverse lignins for heating rates from 10 °C/min to 5000 °C/s to temperatures from 430 to 950 °C with contact times of several seconds. Predicted tar yields increase for progressively lighter lignin MWDs, and accurately depict how variations in lignin MWD affect total volatiles yields. The strong impact of lignin MWD on its primary devolatilization behavior is accurately interpreted by the flash distillation analogy without any adjustments to the reaction kinetics for a diverse assortment of lignins. The entire reaction mechanism in bio-FLASHCHAIN® is required with non-pyrolytic lignins, whose predicted total and tar yields increase in inverse proportion to reductions in MW. For pyrolytic lignins, bridge scission is superfluous because the whole lignin falls within the size range for tar precursors initially and throughout devolatilization. Consequently, neither total nor tar yields are affected by MW variations because the tar vaporization rates are maximized throughout this MW range. Devolatilization shifts toward hotter temperatures for progressively faster heating rates, in good agreement with data, whereas predicted total and tar yields are insensitive to heating rate variations. Total yields increase for progressively hotter temperatures due to the transition from tar production to char decomposition in the reaction mechanism. Tar yields saturate to an asymptotic ultimate value at approximately 550 °C for fast heating rates.

Influence of Base-Catalyzed Organosolv Fractionation of Larch Wood Sawdust on Fraction Yields and Lignin Properties

Lignocellulose-based biorefineries are considered to play a crucial role in reducing fossil-fuel dependency. As of now, the fractionation is still the most difficult step of the whole process. The objective of this study is to investigate the potential of a base-catalyzed organosolv process as a fractionation technique for European larch sawdust. A solvent system comprising methanol, water, sodium hydroxide as catalyst, and anthraquinone as co-catalyst is tested. The influence of three independent process variables, temperature (443–446 K), catalyst loading (20–30% w/w), and alcohol-to-water ratio (30–70% v/v), is studied. The process conditions were determined using a fractional factorial experiment. One star point (443 K, 30% v/v MeOH, 30% w/w NaOH) resulted in the most promising results, with a cellulose recovery of 89%, delignification efficiency of 91%, pure lignin yield of 82%, residual carbohydrate content of 2.98% w/w, and an ash content of 1.24% w/w. The isolated lignin fractions show promising glass transition temperatures (≥424 K) with high thermal stabilities and preferential O/C and H/C ratios. This, together with high contents of phenolic hydroxyl (≥1.83 mmol/g) and carboxyl groups (≥0.52 mmol/g), indicates a high valorization potential. Additionally, Bjorkman lignin was isolated, and two reference Kraft cooks and a comparison to three acid-catalyzed organosolv fractionations were conducted.

Liquid–Liquid Equilibrium Compositions and Global Phase Behavior for Lignin–Acetone–Water Ternary at 25, 45, and 65 °C

Liquid–liquid equilibrium (LLE) phase compositions and tie lines were measured for the lignin–acetone–water system in the region of LLE where the aqueous lignin purification with hot agents (ALPHA)...

Pretreatment of mulberry stem by cholinium-based amino acid ionic liquids for succinic acid fermentation and its application in poly(butylene) succinate production

Cholinium-glycinate ([Ch][Gly]) and cholinium-alanate ([Ch][Ala]) were investigated on the pretreatment of mulberry stem (MS). It resulted in an increase of glucose from 14% to more than 74% compared to the untreated sample. Pretreatment by reused [Ch][Gly] showed good performance for delignification of >60%, and improved structural polysaccharide digestion. Each fractional component has high potential for lignin purification, and succinic acid fermentation. The extracted lignin with [Ch][Gly] showed >90% purity with good qualities of aromatic unit as confirmed by FT-IR and 1H NMR spectra. The carbohydrate rich material was employed for succinic acid fermentation with the highest yield of succinic acid more than 0.89 gsuccinic acid/gglucose. After purification, poly(butylene) succinate (PBS) was synthesized, and was characterized in comparison to commercial PBS.

Sorption behavior of malachite green onto pristine lignin to evaluate the possibility as a dye adsorbent by lignin

The objective of this study was to evaluate the adsorption characteristics of malachite green (MG) on pristine lignin as a dye adsorbent. The adsorption capacity of MG on lignin (31.2 mg/g) was described by Langmuir isotherm and pseudo second order models, and were higher than humic acid (6.4 mg/g). The adsorption of MG by lignin was rapid occurring within 15 min of the reaction, and then equilibrium was reached. The adsorption of MG by lignin based on an intraparticle diffusion model indicated that it was dominated by external boundary. Removal of MG by lignin can be applied at a wide range of pH’s (2–5), and optimal lignin dosage for MG removal was 3 g/L. In addition, the desorption efficiency of MG adsorbed on lignin was highest in methanol + acetic acid (95:5%, v/v) mixture of all solutions tested. The peaks attributed to the hydrogen-bonded stretching vibrations and sulphonyl groups in lignin before MG adsorption, were assigned at about 3400 and 620 cm−1, while the peaks in lignin after MG adsorption were attenuated or reduced. This result indicates that the adsorption of MG by lignin is closely related to the O–H and S–O bonds. Finally, this study suggests that pure lignin, which excludes active processes, can also be used as an adsorbent for dyes. However, in order to utilize the dye-adsorbed lignin repeatedly, further studies will be needed.

Investigating the possibility of making lignin-glyoxal resins as adhesives in the production of plywood

The possibility of making glues of natural origin (pure lignin and lignin-gluoxal (instead of chemical resins for making plywood from poplar layer was investigated. For this purpose, lignin was reacted with glyoxal and the lignin-glyoxal glue was produced. To make the desired plywood, pure lignin (L.100%), lignin-glyoxal 15% (L.85%, G.15%), and lignin-glyoxal 30% (L.70%, G.30%) were used as the adhesive at three different levels. Ammonium chloride (1%) as the hardener and wheat flour (30%) as the filler based on the dry weight of the adhesive were also used. Plates made with urea formaldehyde resin at 160 g/m2 were considered as control samples. After the laboratory boards were produced, the physical and mechanical properties of samples, such as thickness swelling after 2 and 24 h of immersion in water, shear strength, modulus of rupture and modulus of elasticity, were measured. In addition, the groups and bonds in the pure lignin and lignin-gloxal adhesives were identified by Fourier transform infrared (FTIR) spectroscopy. In most tests and compared to the boards made of the adhesives and control boards, the lignin-glyoxal 30% (L.70%, G.30%) glue came closest to the performance of the control glue.