Lignin Particles Research Articles

Numerical modeling and validation of hydrothermal liquefaction of a lignin particle for biocrude production

Lignin liquefaction process under catalyst-free conditions in a temperature range from 573 K to 647 K is investigated with this mathematical model. Based on the theoretical understanding of the physical and chemical processes of the liquefaction process in subcritical temperatures, a comprehensive mathematical model for the decomposition of lignin by hydrolysis reaction pathway is developed on the results of a series of batch experiments. The model consists of four main sections. They are liquefaction of lignin particle, oily film, and inorganic (ash) layer formation behavior during the liquefaction, kinetic model to model further liquefaction process of initial products, and the layer model for the intraparticle processes. Hydrolysis of the lignin particle is modeled using the shrinking core concept. The formation of oily film and an inorganic layer around the lignin particle and their behavior is modeled considering water transport through layers, diffusion of products, and dissolution of products in water. Moreover, the layer model is used to obtain surface and center point temperatures of the particle using mass transfer. .The kinetic model consists of ten components and 21 reactions. . Variations of aromatic hydrocarbons and phenolic compounds are given significance. In the experimental study highest biocrude yield of 0.28 w/w0 is obtained at an operating temperature of 573 K. Aromatic hydrocarbons are reduced from 0.23 w/w0 to 0.145 w/w0 with the increase of operating temperature from 573 K to 623 K. For an increase of operating temperature from 573 K to 623 K, phenol shows an increase from 2.5 × 10−4 w/w0 to 3 × 10−3 w/w0. At 573 K and with a particle of radius 0.08 mm, oily film and ash layer show a maximum thickness of 2 × 10−12 m and 7.5 × 10−3 m, respectively. Both oily film and ash layer show a faster formation and faster dissolution in water with increasing operating temperature. Finally, the model's liquefaction results are analyzed and validated with the experimental data and the literature data, where it shows a reasonable agreement.

Colloidal Lignin Particles and Epoxies for Bio-Based, Durable, and Multiresistant Nanostructured Coatings.

There is a need for safe and sustainable alternatives in the coating industry. Bio-based coatings are interesting in this perspective. Although various oils and waxes have been used as traditional wood coatings, they often lack sufficient durability. Lignin is an abundant natural polyphenol that can be used to cure epoxies, but its poor water solubility has impeded the use of unmodified lignin in coatings in the past. To address this issue, water-dispersible colloidal lignin particles (CLPs) and an epoxy compound, glycerol diglycidyl ether (GDE), were used to prepare multiprotective bio-based surface coatings. With the GDE/CLP ratios of 0.65 and 0.52 g/g, the cured CLP–GDE films became highly resistant to abrasion and heat. When applied as a coating on wooden substrates, the particulate morphology enabled effective protection against water, stains, and sunlight with very thin layers (less than half the weight of commercial coatings) while retaining the wood’s breathability excellently. Optimal hydrophobicity was reached with a coat weight of 6.9 g(CLP)/m2, resulting in water contact angle values of up to 120°. Due to their spherical shape and chemical structure, the CLPs acted as both a hardener and a particulate component in the coating, which removed the need for an underlying binding polymer matrix. Light interferometry measurements showed that while commercial polymeric film-forming coatings smoothened the substrate noticeably, the particulate morphology retained the substrate’s roughness in lightweight coatings, allowing for a high water contact angle. This work presents new strategies for lignin applications in durable particulate coatings and their advantages compared to both currently used synthetic and bio-based coatings.

Valorization of Rice Straw via Hydrotropic Lignin Extraction and Its Characterization.

Rice straw hydrotropic lignin was extracted from p-Toluene sulfonic acid (p-TsOH) fractionation with a different combined delignification factor (CDF). Hydrotropic lignin characterization was systematically investigated, and alkaline lignin was also studied for the contrast. Results showed that the hydrotropic rice straw lignin particle was in nanometer scopes. Compared with alkaline lignin, the hydrotropic lignin had greater molecular weight. NMR analysis showed that β-aryl ether linkage was well preserved at low severities, and the unsaturation in the side chain of hydrotropic lignin was high. H units and G units were preferentially degraded and subsequently condensed at high severity. High severity also resulted in the cleavage of part β-aryl ether linkage. 31P-NMR showed the decrease in aliphatic hydroxyl groups and the increasing carboxyl group content at high severity. The maximum weight loss temperature of the hydrotropic lignin was in the range of 330–350 °C, higher than the alkaline lignin, and the glass conversion temperature (Tg) of the hydrotropic lignin was in the range of 107–125 °C, lower than that of the alkaline lignin. The hydrotropic lignin has high β-aryl ether linkage content, high activity, nanoscale particle size, and low Tg, which is beneficial for its further valorization.

Ultralow loading mussel-inspired conductive hybrid as highly effective modifier for function-engineered poly(lactic acid) composites

It remains a great challenge to prepare polylactic acid (PLA) composites with excellent mechanical properties, superior anti-bacteria, and highly effective electromagnetic interference (EMI) shielding using ultralow loading of functional fillers. Herein, lignin particles were uniformly nano-sized as the matrix reinforcement and the fillers carrier via green mechanochemistry for improved thermal properties of polymer matrix. Through one-pot approach to a multitasking engineered agent, hybridized ZnO/Ag particles were synthesized for multi-functionalities. Inspired by mussels, the bio-derived dopamine cross-linker was introduced to in-situ synthesize the polypyrrole (PPy-PDa) glutinous nanofibrils as an interfacial modifier and a particles dispersant to regulate surface free energy of nanoparticles and improve filler-matrix interactions. With effective constructed 3D conductive networks by glutinous nanofibrils and hybridized particles, the dramatic improvement in EMI shielding and electrical conductivity was accomplished using an ultralow content of the conductive particles modifier (0.29 vol% Ag). The resulted biobased composites presented outstanding anti-dripping properties, mechanical properties, electrical conductivity (104.2 S/cm), anti-bacteria, joule heating, photothermal conversion ability and EMI shielding effectiveness (48.6 dB at X-band), which are superior to those reported. This work will broaden the application prospects of PLA composites in the fields of wearable electronics, food packaging and medical devices.

Ultrafine Friction Grinding of Lignin for Development of Starch Biocomposite Films.

The work demonstrates the utilization of fractionalized lignin from the black liquor of soda pulping for the development of starch-lignin biocomposites. The effect of ultrafine friction grinding on lignin particle size and properties of the biocomposites was investigated. Microscopic analysis and membrane filtration confirmed the reduction of lignin particle sizes down to micro and nanoparticles during the grinding process. Field Emission Scanning Electron Microscopy confirmed the compatibility between lignin particles and starch in the composites. The composite films were characterized for chemical structure, ultraviolet blocking, mechanical, and thermal properties. Additional grinding steps led to the reduction of large lignin particles and the produced particles were uniform. The formation of 7.7 to 11.3% lignin nanoparticles was confirmed in the two steps of membrane filtration. The highest tensile strain of the biocomposite films were 5.09 MPa, which displays a 40% improvement compared to starch films. Further, thermal stability of the composite films was better than that of starch films. The results from ultraviolet transmission showed that the composite films could act as an ultraviolet barrier in packaging applications.

Effect of boron-based additives on char agglomeration and boron doped carbon microspheres structure from lignin pyrolysis

To prevent the thermal softening of lignin during the pyrolysis process, the influence of boron-based additives (boric acid, sodium borate and potassium borate) on lignin softening, pyrolysis process were investigated with metal bases (Ca(OH)2 and Mg(OH)2) as comparison, and the influence mechanism of boron based additives was explored in depth. It is found that the boron additives can effectively inhibit the agglomeration of lignin particles. For pyrolysis products, boron additive promoted the carbon-forming reaction of lignin with carbon sequestration more than 70 wt%, and inhibited the release of volatiles, especially for phenolic compounds. It also inhibited the generation of CO2 and CH4, while promoted the release of CO. The boron element in lignin char mainly exists in the form of BCO2 and B2O3 with more hydroxyl groups on the surface. Furthermore, boron-modified lignin chars are spherical with more uniform and smaller particle size compared with metal bases modified lignin chars.

Preparation and performance of lignin-based waterborne polyurethane emulsion

The unmodified industrial Alkali Lignin (AL) was used as a hydrophilic chain extender to prepare a series of Lignin-based Waterborne Polyurethane (LWPU) emulsions with different lignin contents by step-growth addition polymerization with polypropylene glycol (PPG) and isophorone diisocyanate (IPDI). The lignin content in the series of LWPUs was determined by elemental analysis, with a maximum content of 24.68 wt%. The infrared spectrum and SEM diagram of the LWPU film show that the AL reacts well with isocyanate, the section of the film is flat and smooth, and there are no agglomerated lignin particles in the film, which indicates that the film is homogeneous. With the increase of AL content, the particle size of the LWPU emulsion decreased gradually from 233 nm to 127 nm, the Zeta potential decreased gradually from -44.8 mV to -56.9 mV, and the emulsion has good stability in the pH range of 5–12. The thermogravimetric analysis of the LWPU film show that the introduction of AL can improve the thermo stability of the polyurethane material, and the mechanical properties test results show that the highest tensile strength of the LWPU film can reach 1.29 times that of the pure polyurethane film. Ultraviolet aging test show that the introduction of AL can significantly improve the UV aging resistance of the polyurethane film. The lignin-based waterborne polyurethane emulsion prepared in this study can be used as a new type of bio-based polyurethane material.

Benzenesulfonic acid-based hydrotropic system for achieving lignocellulose separation and utilization under mild conditions

Developing low-cost and sustainable fractionation technology is the key to achieve the maximal utilization of lignocellulosic biomass. This study reported benzenesulfonic acid (BA) as a green hydrotrope for efficient lignocellulose conversion into two fractions at atmospheric pressure: (1) a primarily cellulosic solid residue that can be utilized to produce high-value building blocks (lignocellulosic nanomaterials or sugars), and (2) the collected spent acid liquor that can be diluted with anti-solvent to easily obtain lignin nanoparticles. BA hydrotropic method exhibited greater reaction selectivity to solubilize lignin, where approximately 80% lignin were removed at only 80 °C in 20 min. The lower lignin content substrates resulted in relatively higher enzymatic hydrolysis efficiency of 80% and less entangled lignocellulosic nanofibrils (LCNF). Furthermore, the separated lignin particles size can be easily adjusted by the initial acid concentration. Overall, this work presented a promising and simple technology in achieving lignocellulose separation and utilization under mild conditions.

Preparation of novel all-lignin microcapsules via interfacial cross-linking of pickering emulsion

Lignin based microcapsules are highly attractive for protect easy photolysis substances. However, so far, all-lignin microcapsules prepared with water-soluble lignin are not satisfactory in terms of wall thickness and mechanical properties. Herein, we fabricated a novel all-lignin microcapsules (ALMC) by using 1,6-dibromohexane or epichlorohydrin to crosslink lignin particles adsorbed at the Pickering emulsion droplets interface. 1, 6-Dibromohexane demonstrated a stronger cross-linking activity than epichlorohydrin, and could be used in less dosage and at lower temperatures. The shell thickness of ALMC was about 300 nm. Further analysis confirmed that the shell had a double-layer structure, the outer layer was rough and shrinking and the inner layer was smooth and dense. ALMC can be used to encapsulate hydrophobic substances, and a photosensitive pesticide avermectin (AVM) was chosen to be sealed as model object. The AVM-encapsulated ALMC showed ideal sustained-release performance, namely releasing slowly in the early stage without affecting the overall release. After 70 h of UV irradiation, 93.7 % of AVM was retained, while the original AVM without encapsulation almost all of them was photodegraded, which means that the ultraviolet absorption property of lignin provides excellent protection for the core materials.

Toward waste valorization by converting bioethanol production residues into nanoparticles and nanocomposite films

A “waste-valorization” approach was developed to transform recalcitrant hydrolysis lignin (HL) from second-generation bioethanol production into multifunctional bio-based products. The hydrolysis lignin (HL) was extracted with aqueous acetone, yielding two fractions enriched in lignin and cellulose, respectively. The soluble hydrolysis lignin (SHL) was converted into anionic and cationic colloidal lignin particles (CLPs and c-CLPs). The insoluble cellulose-rich fraction was transformed into lignocellulosic nanofibrils that were further combined with CLPs or c-CLPs to obtain nanocomposite films with tailored mechanical properties, oxygen permeability and antioxidant properties. To enable prospective applications of lignin in nanocomposite films and beyond, CLPs and c-CLPs were also produced from a soda lignin (SL) and the influence of the lignin type on the particle size and ecotoxicity was evaluated. Finally, the carbon footprint of the entire process from hydrolysis lignin to films was assessed and an integration to industrial scale was considered to reduce the energy consumption. While most previous work utilizes purified lignin and pristine and often purified cellulose fibers to produce nanomaterials, this work provides a proof of concept for utilizing the recalcitrant lignin-rich side stream of the bioethanol process as raw material for functional nanomaterials and renewable composites.

State-of-the-Art: Applications and Industrialization of Lignin Micro/Nano Particles.

As a new product of high-value utilization of lignin, lignin micro/nano particles (LMNPs) have attracted the attention of researchers due to their non-toxicity, corrosion-resistance, UV resistance, and other excellent characteristics and potential application value. This article outlined the main preparation methods of LMNPs at the current stage, summarized and compared them from three perspectives of preparation technology, final product state and product composition. Subsequently, based on the different focuses of the properties of LMNPs, their application research progress as fillers, UV blockers, drug delivery carriers, among others, were introduced. Then a concise analysis of the technical and economic assessment and life cycle assessment of LMNPs in the process of industrialization was made. Finally, the main problems at present and the future development directions were analyzed and prospected to provide references for the deep processing of forest resources and the development of bio-based nanomaterials.

Biobased “rigid-to-stretchable” conversion for strong and tough poly(lactic acid) with UV-protective property

• Hetero-profiled morphology of lignin-based complex for “rigid-to-stretchable” conversion for the first time. • Specialized assembly of particles for the recalcitrant issues of interfacial compatibility and filler dispersion. • Rigidity-sourced complex as toughening plasticizer and interfacial modifier for improved toughness, stiffness, strength and excellent anti-ultraviolet properties. The major obstacles to expand the applications of biodegradable poly(lactic acid) (PLA) are the poor toughness and the lack of UV protection in many fields, such as food and goods packaging. In this work, a bio-based “rigid-to-stretchable” conversion approach was presented for the first time to construct the plasticized lignin-based complex through mechanochemistry for the simultaneous improvement of toughness and strength on PLA matrix. With the aid of polymer-based surfactants as an interfacial modifier, the rigid lignin particles were significantly softened through a facile and green ball-milling process to form the plasticized complex with hetero-profiles. Apart from the conventional approach to the rubber-like toughener, the morphology-structured lignin-based complex was controllably regulated as the rigidity-sourced plasticizer to address the recalcitrant issues of interfacial compatibility and dispersion. With the strong and tough PLA-based composite films (PLA/Lg@TWN) successfully prepared, the tensile strength and the ultimate elongation simultaneously increases to 58.2 MPa and 32.5 % compared to those of the neat PLA of 15.8 MPa and 15.7 % respectively. The toughness was also enhanced from 7.21 MJ/m 3 for pure PLA to 15.57 MJ/m 3 for PLA/Lg@TWN. The specialized assembly of bio-derived aromatic structures was conducive to exploring ultraviolet resistance, exhibiting superb UV absorption property in UV A (100 %) and UV B (99.5 %) range compared to low UV absorption of UV A (57 %) and UV B (75 %) for neat PLA. Therefore, the developed multifunctional PLA films would present the promising potential for applications in the fields of packaging and agricultural materials with favorable mechanical properties and UV protection performance.

On-site and quantitative SERS detection of trace 1, 2, 3-benzotriazole in transformer oil with colloidal lignin particles-based green pretreatment reagents

Since 1, 2, 3-Benzotriazole (BTA) is one of the most commonly used metal passivators in transformer oil, on-site and quantitative detection of BTA plays a significant role in fast evaluation of the performance of the insulating oil. Herein, we proposed a cycle-growth synthetic protocol for yielding two-dimensional (2D) plane-based surface-enhanced Raman scattering (SERS) substrates with tunable optical property and controllable interparticle distance, and an extraction material, so called colloidal lignin particles (CLPs), for the fast separation of BTA from oil matrix. After BTA from transformer oil were adsorbed by hydrophilic CLPs, highly reproducible SERS signal of BTA can be obtained by dropping on the substrate. The characteristic Raman shift at 1386 cm−1 of BTA has been selected to establish a good linearity between its relative intensity and concentration in the range of 1–300 mg/L, and the detection limit for BTA was down to 0.12 mg/L. Moreover, the time consumption for the whole detection process of real sample including sample pretreatment and SERS measurements was less than 30 min. It is highly expected that the combination of CLPs with SERS can accomplish the on-site detection of trace BTA in transformer oil.

Understanding lignin micro- and nanoparticle nucleation and growth in aqueous suspensions by solvent fractionation

Interactions of sub-micron lignin particles dependent on precursor kraft lignin chemistry and molecular weight.

エアロゾルフローリアクターを用いたリグニン粒子のハイスループット合成：サイズ分画とピッカリングエマルションへの応用

エアロゾルフローリアクターを用いたリグニン粒子のハイスループット合成：サイズ分画とピッカリングエマルションへの応用

Well-Defined Lignin Model Films from Colloidal Lignin Particles.

The transformation of a molecularly complex and irregularly shaped lignin into a nanoscale spherical architecture is anticipated to play a pivotal role in the promotion of lignin valorization. From the standpoint of using colloidal lignin particles (CLPs) as building blocks for a diverse range of applications, it has become essential to study their interactions with soluble compounds of varied origin. However, the lack of model films with well-defined surface properties similar to those of CLPs has hindered fundamental studies using surface-sensitive techniques. Here, we report well-defined and stable thin films prepared from CLPs and demonstrate their suitability for investigation of surface phenomena. Direct adsorption on substrates coated with a cationic anchoring polymer resulted in uniform distribution of CLPs as shown with atomic force microscopy (AFM). Quartz crystal microbalance with dissipation monitoring (QCM-D) experiments revealed higher adsorbed mass of cationic lignin onto the CLP-coated substrate in comparison to the film prepared from dissolved lignin, suggesting preferential adsorption via the carboxylic acid enriched surfaces of CLPs. QCM-D further enabled detection of small changes such as particle swelling or partial dissolution not detectable via bulk methods such as light scattering. The CLP thin films remained stable until pH 8 and displayed only a low degree of swelling. Increasing the pH to 10 led to some instability, but their spherical geometry remained intact until complete dissolution was observed at pH 12. Particles prepared from aqueous acetone or aqueous tetrahydrofuran solution followed similar trends regarding adsorption, pH stability, and wetting, although the particle size affected the magnitude of adsorption. Overall, our results present a practical way to prepare well-defined CLP thin films that will be useful not only for fundamental studies but also as a platform for testing stability and interactions of lignin nanoparticles with materials of technical and biomedical relevance.

Copper Adsorption on Lignin for the Removal of Hydrogen Sulfide.

Lignin is currently an underutilized part of biomass; thus, further research into lignin could benefit both scientific and commercial endeavors. The present study investigated the potential of kraft lignin as a support material for the removal of hydrogen sulfide (H2S) from gaseous streams, such as biogas. The removal of H2S was enabled by copper ions that were previously adsorbed on kraft lignin. Copper adsorption was based on two different strategies: either directly on lignin particles or by precipitating lignin from a solution in the presence of copper. The H2S concentration after the adsorption column was studied using proton-transfer-reaction mass spectrometry, while the mechanisms involved in the H2S adsorption were studied with X-ray photoelectron spectroscopy. It was determined that elemental sulfur was obtained during the H2S adsorption in the presence of kraft lignin and the differences relative to the adsorption on porous silica as a control are discussed. For kraft lignin, only a relatively low removal capacity of 2 mg of H2S per gram was identified, but certain possibilities to increase the removal capacity are discussed.

Toughening of natural rubber nanocomposites by the incorporation of nanoscale lignin combined with an industrially relevant leaching process

Strong and tough nanocomposite materials based on natural rubber (NR) latex demonstrate increasing potential to be used in advanced engineering applications and personal care products. Among many approaches for improving the toughness of NR-based products, the use of renewable and bio-based nanofillers is persuaded by environmental and economic trends. In this study, we report the preparation and incorporation of nanoscale organosolv lignin (OSL) particles in NR latex to improve its mechanical properties. We showed that the tensile strength, toughness, and Shore hardness of NR films reinforced with 5 wt % nanoscale OSL were improved by 39 %, 53 % and 12 %, respectively, while retaining high elongation at break (∼1800 %). This substantially improved mechanical property profile can be attributed to the enhanced nanoscale dispersion of OSL and the associated favourable interfacial adhesion of OSL with the NR matrix. Furthermore, the impact of an industrially applicable leaching process on the toughness and thermo-oxidative stability of rubber films is also discussed. For an instance, after the leaching process, the tensile strength, elongation, and toughness of 1 wt % OSL/NR were increased by 27 %, 9 %, and 32 %, respectively.

Effects of cellulose, hemicellulose, and lignin on the combustion behaviours of biomass under various oxygen concentrations

The combustion behaviours of three components, namely hemicellulose, cellulose, and lignin, and four types of biomass, namely rice straw, bamboo, peanut shell, and chestnut shell, were examined in a drop tube furnace set at 1273 K, in O2/N2 atmospheres containing 21–100% O2. Radiant energy analysis technology was employed to infer the temperatures of the samples. The results show that the ignition mechanisms of cellulose and hemicellulose change at 30% and 70% O2, respectively, and the lignin particle ignites homogeneously at 20–30% O2, heterogeneously at 50% O2, and hetero-homogeneously at 70–100% O2, respectively. The changes in the ignition mechanisms of biomass particles with lignin content > 10% and < 10% under a certain oxygen concentration depend considerably on the lignin and cellulose contents in the biomass particle, respectively. The expansion of biomass particles with lignin content > 10% and < 10% during combustion process are caused by lignin and hemicellulose, respectively.

Influence of Adding Lignin and Wood as Reactive Fillers on the Properties of Lightweight Wood–Polyurethane Composite Foams

Abstract In this study, bio-based rigid polyurethane (PU) composite foams were prepared by a free-rising method, with the addition of wood particles (10 and 20 weight percent by the foam mass) and kraft lignin (5 and 10 weight percent by the polyol mass) as reactive reinforcing fillers. The resultant PU composites were evaluated for chemical structure, density, morphology, compressive properties, water uptake, and thermal stability. Fourier-transform infrared analysis confirmed the formation of characteristic urethane bonds in all foam samples. The foaming process was slowed down by the incorporation of lignin and wood particles. The apparent density of lignin-incorporated wood–PU composite foam ranged between 77 and 105 g/cm3. Compared with the neat PU foam, addition of wood particle resulted in decreased compressive properties and increased water uptake of the foams, whereas incorporation of lignin had a positive effect on the compressive properties and water resistance. In general, the PU foam sample with the incorporation of only 5 percent lignin (PUL5) exhibited the optimal physical–mechanical properties, with the compressive strength increased by 74 percent and 24-hour water uptake decreased by 28 percent compared with the control PU foam. Thermogravimetric analysis showed that the incorporation of lignin and wood particles did not significantly affect the thermal degradation pattern of foam but rather increased the mass of char residue.