Degree Of Delignification Research Articles

Wood‐inspired High Ionic Conductivity Hydrogel Electrolytes for Flexible Supercapacitors

Hydrogel is a promising electrolyte substrate, but its ionic conductivity needs further improvement. In this paper, we propose a strategy to improve the ionic conductivity of hydrogels with flexible wood and fabricate a flexible wood‐based poly(acrylic acid‐acrylamide) composite hydrogel electrolyte (WHE) by delignification and in‐situ polymerization. The flexible wood as a porous backbone for hydrogels can regulate ion transport pathways to improve the ionic conductivity of hydrogels. The straight pores of wood confine the transport of electrolyte ions along the shortest path, resulting in a high ionic conductivity of 3.0 × 10‐2 S cm‐1, which is great in composite polymer electrolytes. We have systematically investigated the effect of the degree of delignification and the polymerization process on the overall performance of the electrolyte. The optimized supercapacitor exhibits a specific capacitance of 155.64 F g‐1 and an energy density of 7.45 W h kg‐1. The WHE is applied to flexible supercapacitor, which exhibits good flexibility under bending conditions and can maintain similar electrochemical performance at a wide range of bending angles. This work provides an effective strategy for the efficient use of wood resources and the development of low‐cost, environmentally friendly, and high‐performance hydrogel electrolyte materials.

Effects of peracetic acid delignification on hemicellulose extraction by dimethyl sulfoxide

Extracting high-purity and structurally intact hemicelluloses from lignocellulosic fibers is a prerequisite to reveal their structures and realize high-value utilization. Delignification is usually performed before hemicellulose extraction to break the covalent bonds between hemicelluloses and lignin for effective separations, but usually leads to toxic by-products and hemicellulose degradation. Peracetic acid (PAA) is an environmentally friendly oxidizing agent, which is more selective for delignification and has less effect on the primary structure of hemicelluloses. However, the yields and chemical structures of hemicelluloses extracted at different PAA delignification conditions are not clear, which greatly hinders its research and application. Consequently, the response surface methodology (RSM) was used in this study to optimize the process parameters of PAA delignification. With the increase of temperature or time, the yield of holocellulose decreases, and the hemicellulose yield increases first and then decreases. With the increase of delignification degree, the hemicellulose yield increases significantly. The degree of PAA delignification also has a significant effect on the chemical structures of extracted hemicelluloses; hemicellulose samples extracted from highly delignified holocelluloses have a higher xylose unit content, molecular weight (MW) and degree of substitution by acetyl groups (DSAc). The tert-butanol solvent exchange or ball milling treatments on holocelluloses significantly increase the hemicellulose yields, by avoiding the hornification and improving the accessibility of holocellulose. This study will provide theoretical and technical support for the efficient separation of hemicelluloses.

Novel stationary basket reactor for effective biomass delignification with deep eutectic solvent

Biomass pretreatment and conversion are crucial for sustainable development, but lack information on equipment that ensures effective mass transfer and easy biomass separation post-process. This work introduces a novel basket reactor with a stationary bed (StatBioChem) for biomass processing using deep eutectic solvents (DESs). We compared the delignification efficiencies of soft and hard biomass samples processed in the StatBioChem reactor, a stirred tank reactor (STR), and a commercial SpinChem® reactor. The StatBioChem design allowed DES to flow evenly through biomass in the basket, achieving the highest delignification degree, particularly for hard biomass. This effect was not observed in the SpinChem® basket reactor. High delignification led to increased glucose yields in subsequent enzymatic hydrolysis. The StatBioChem effectively combines the simplicity and efficiency of an STR with the ease of solvent recovery typical of basket reactors.

Maximizing the valorization potential of lignin through optimization of the Soda pulping conditions

The valorization potential of lignin is strongly dependent on the yield that can be obtained during the pulping process as well as its chemical structure. Both of these are determined by factors such as the biomass type, the selected extraction strategy and the employed conditions. Within this study, Miscanthus x giganteus biomass was subjected to systematically varying Soda pulping conditions, i.e., temperature (100 °C – 180 °C), OH– concentration (0.158 mol/L – 1.000 mol/L) and time (60 min – 360 min). These pulping conditions can be combined into a single factor, reflecting the processing severity, which in this work varied from approximately 1 to 5. The resulting black liquor, precipitated lignin, lignin stock solution (i.e., lignin dissolved in the solvent used in the subsequent depolymerization step) and product pool after mild reductive catalytic depolymerization (200 °C, 10 bar H2 initial, 4 h) were thoroughly characterized using a plethora of analysis techniques. Increasing the severity factor of the pulping was found to result in an enhancement of the delignification degree from 25.3 ± 2.6 % to 95.4 ± 9.9 %. However, beyond a severity factor of 3, fragmentation of native ether linkages and condensation reactions start to cause unfavourable changes in the chemical structure of the lignin and depolymerization product pool. Furthermore, these reactions significantly reduce the total mass yield from biomass to depolymerization product pool. An Adaboost model with quadratic base estimator was trained against the experimental data, and subsequently used to optimize the pulping conditions, aiming at a maximum total mass yield with minimal fragmentation and, hence, condensation, of the lignin. The optimum was experimentally validated, which resulted in a lignin with high β-O-4 content (42.7 ± 2.8 linkages per 100 aromatic units) and a total mass yield of 30.9 ± 3.4 wt% and a pulp with a residual lignin content of 8.25 ± 0.94 wt%.

The corrected H/G factors for accurately describing the delignification and depolymerization of industrial hemp stalks

Establishment of precise kinetic models is beneficial for the control of the degree of delignification and carbohydrate degradation in the pulping process. However, most kinetic models judge the degree of delignification and depolymerization only by holding time or fluctuating temperature, ignoring the effects of temperature and heating-up stage. Thus, this study explored in depth the delignification and depolymerization kinetic behaviors of the kraft pulping process of alkali-extracted hemp stalk material (HSM-AE). The chemical composition characteristics of the HSM-AE were firstly studied, followed by the investigation of the HSM-AE kraft pulping under different conditions. The H/G factor of the wood raw material was not suitable to describe the delignification and depolymerization behaviors during HSM-AE kraft pulping and needs to be corrected. Based on the corrected H/G factors, kinetic models of delignification and depolymerization were established. The parameter fitting results showed that the delignification and depolymerization were mainly dominated by sulfide cleavage and alkaline hydrolysis respectively. The activation energies of delignification caused by alkaline- and sulfide- cleavages were 66.8 and 72.7 kJ/mol; and the activation energies of cellulose depolymerization caused by peeling reaction and alkaline hydrolysis were 111.7 and 120.5 kJ/mol, respectively. Compared with eucalyptus kraft pulping, the activation energy ratio of delignification to cellulose depolymerization decreased, indicating that under the same delignification degree, the cellulose in HSM-AE was easier to alkaline degrade. At present, the process described in this experiment was more suitable to prepare dissolving-grade pulp for further production of viscose staple fiber.

Model-based process intensification of deep eutectic solvent treatment of eucalyptus slabs for lignin extraction and pulp production

This work revealed the reaction characteristics in the delignification process of eucalyptus slabs catalyzed by acidic deep eutectic solvent (benzyltriethylammonium chloride/formic acid) from the perspective of heterogeneous reactions. The limitation of internal diffusion on delignification process cannot be ignored. Afterwards, a kinetic model based on cell wall structure was proposed to describe the relationship between the delignification degree and reaction conditions, and it also hold excellent predictive ability for lignin removal, carbohydrate retention and solid residue yield. Compared with other reported kinetic models, this novel model not only took into account all operational parameters of reaction process, but also can be applied to the entire reaction process without the need for segmentation. Besides, an essential requirement based on the developed model was a 44.40 wt% formic acid concentration and a temperature of 130 °C, when the purpose of DES treatment was pulping. Generally, this work could provide guidance on process adjustments and product quality control during the DES processing.

Influence of pulping conditions on the pulp yield and fiber properties for pulping of spruce chips by deep eutectic solvent

AbstractThe chemical pulping of wood chips using deep eutectic solvents (DES-pulping) has emerged as an alternative technology to conventional pulping in the paper industry, allowing the production of pulp in combination with the recovery of lignin and sugars for valorization. A challenge in the development of this technology is the understanding of how the operating conditions influence the crucial pulp manufacturing parameters such as delignification percentage, pulp yield, and fiber quality. This work is focused on investigating the effect of operating conditions such as cooking temperature, cooking time, liquor-to-wood ratio, initial water content on DES, type of mixing, the addition of a pre-treatment step (pre-impregnation of DES into the wood chips) to cooking process, and DES composition (lactic acid:choline chloride, lactic acid:sodium chloride, and lactic acid:sodium bromide) on the cooking of wood chips by DES. A shortcut quality evaluation parameter (Q), defined as the product of the fiber length and the degree of delignification quantified the quality of the pulping process in a single value, shows values similar to a reference unbleached kraft pulp for cooking at 130 °C in a range of cooking times from 3 to 4.5 h at a L/W of 10:1 by using lactic acid:choline chloride DES. More elaborate property analysis on the fibers showed that several of the the quality-indicating properties of the fibers (coarseness, shape factor, fibril area, and crill index) are comparable with typical sulfite pulping fibers.

Optimization of delignification depth of wood surfaces for skin polymer impregnation

We controlled the degree of surface delignification of a wood specimen to impart functionality to its surface and injected a polymer into the porous structure to investigate using it as a functional material. Generally, balsa wood is used in studies aiming to impart functionality through polymer impregnation. However, we used a native Korean tree (Paulownia tomentosa), which has the lowest specific gravity. Peracetic acid (acetic acid and hydrogen peroxide mixture) was used as the delignification solution. Changes in wood surface properties were analyzed according to the delignification treatment duration. Changes in chemical composition, functional groups, cell wall structure, specific gravity, and pores were also observed. Depending on the delignification time, the specific gravity decreased from 0.24 to 0.12. The lignin content was reduced from 29.2% to 0.9%. Fourier Transform Infrared Spectroscopy revealed changes in the lignin functional groups (1 591, 1 507, and 1 240 cm−1), and changes in functional groups derived from hemicellulose (1 720 and 1 182 cm−1). Epoxy infiltration depth was adjusted according to delignification treatment depth to impart wood surface functionality. Our research results indicated that strength and durability could be improved by selectively impregnating polymers into the wood surface requiring functionality, unlike chemically modifying the entire interior of the wood.

Pulp delignification and refining: impact on the supramolecular structure of softwood fibers

The effect on softwood fiber wall nanostructure of kraft cooking, oxygen delignification and refining was evaluated by X-ray scattering. A recently developed simulation method for modelling small angle X-ray scattering (SAXS) data was used to estimate the apparent average sizes of solids (AAPS) and interstitial spaces in the fiber wall (AACS). Fiber saturation point and wide angle X-ray scattering were also used to calculate the pore volume in the fiber wall and the crystallite size of the fibril, respectively. The experimental modelled SAXS data was able to give consistent values for each kraft-cooked and oxygen-delignified pulp. Kraft delignification seems to have the major influence on the fiber nanostructure modification, while oxygen delignification has little or no significant impact even for different kappa numbers. The particle sizes values were more stable than the cavities sizes and no significant differences were seen between different delignification processes, refining or delignification degree. Pulps evaluated after PFI-refining, showed an increase in the fiber wall porosity evaluated by FSP and an increase in the interstitial spaces in the fiber wall, while the crystallite size and the particle sizes were very little or not affected at all.

Highly anisotropic and elastic cellulosic scaffold guiding cell orientation and osteogenic differentiation via topological and mechanical cues

Inspired by the similarity of anisotropic channels in wood to the canals of bone, the elastic wood-derived (EW) scaffolds with anisotropic channels were prepared via simple delignification treatment of natural wood (NW). We hypothesize that the degree of delignification will lead to differences in mechanical properties of scaffolds, which in turn directly affect the behaviors and fate of stem cells. The delignification process did not destroy the anisotropic channel structure of the scaffolds, but endowed the scaffolds with good elasticity and rapid stress relaxation. Interestingly, the micron-scale anisotropic channels of the scaffolds can highly promote the polarization of cells along the direction of channels. We also found that the alkaline phosphatase of EW scaffold can reach to about 13.1 U/gprot, which was about double that of NW scaffold. Moreover, the longer the delignification time, the better the osteogenic activity of the EW scaffolds. We further hypothesize that the osteogenic activity of scaffolds is related to the stress relaxation properties. The immunofluorescence staining showed that when the stress relaxation time of scaffold was shortened to about 10 s, the nuclear ratio of YAP of scaffold increased to 0.22, which well supports our hypothesis.

Improving the Cellulose Enzymatic Digestibility of Sugarcane Bagasse by Atmospheric Acetic Acid Pretreatment and Peracetic Acid Post-Treatment.

Pretreatment of sugarcane bagasse (SCB) by aqueous acetic acid (AA), with the addition of sulfuric acid (SA) as a catalyst under mild condition (<110 °C), was investigated. A response surface methodology (central composite design) was employed to study the effects of temperature, AA concentration, time, and SA concentration, as well as their interactive effects, on several response variables. Kinetic modeling was further investigated for AA pretreatment using both Saeman's model and the Potential Degree of Reaction (PDR) model. It was found that Saeman's model showed a great deviation from the experimental results, while the PDR model fitted the experimental data very well, with determination coefficients of 0.95-0.99. However, poor enzymatic digestibility of the AA-pretreated substrates was observed, mainly due to the relatively low degree of delignification and acetylation of cellulose. Post-treatment of the pretreated cellulosic solid well improved the cellulose digestibly by further selectively removing 50-60% of the residual linin and acetyl group. The enzymatic polysaccharide conversion increased from <30% for AA-pretreatment to about 70% for PAA post-treatment.

Morphological Differences between Virgin and Secondary Fibers

The properties of the fibers determine the quality of the pulp and, thus, the quality of the paper made from it. Recognition of properties, which fiber and paper pulp should be characterized by, in order to achieve required paper properties, is, therefore, a subject of research and interest of many papermaking research experts and scientists. Fibers are subject to deformation and possible weakening under the influence of chemical and mechanical factors, and therefore the quality of the fibers decreases each time they are used in production when it comes to recycled pulps. Then again, the key factor determining the quality of the primary fiber is the degree of pulp delignification. In the article, an attempt was made to define the impact of delignification of virgin pulp on morphological properties of fibers, and compare them with the properties of recycled paper pulp, in order to find correlations. The current economic and raw material situations in the wood market force one to seek new solutions to limit the use of virgin fibers, which is extremely important for the economy of the paper mill, environmental protection and raw material management.

Enhanced catalytic cleavage of C-O and C-C bonds of raw biomass into lignin monomers and glucose

Reductive catalytic fractionation (RCF) of lignocellulose has been considered to be a promising strategy for the separation and subsequent upgradation of biomass constituents. However, the recalcitrant C-C bonds in lignin were the major limitation to produce aromatic monomers in high yield for the hydrogenolysis of lignocellulosic biomass under mild conditions. Herein, an efficient approach was developed to catalytic in-situ hydrogenolysis of solid biomass into lignin monomers and glucose using Ni-Al catalyst with Ni2Al3 alloy phase. 62.9 wt% of aromatic monomers yield was achieved with the degree of delignification up to 89.8 %. Two-dimensional heteronuclear single quantum correlation nuclear magnetic resonance (2D HSQC NMR) spectrum emerged that the C-O and C-C bonds involving β-O-4, β-β and β-5 linkages were all catalytically broken. Moreover, the cellulose was recovered with the cellulose retention and purity of 80.1 % and 88.2 %, respectively, which was further enzymatically hydrolyzed to glucose with the yield of 92 %. Overall, the efficient fractionation and transformation of biomass constituents were realized simultaneously.

Comparative study of acid- and alkali-catalyzed 1,4-butanediol pretreatment for co-production of fermentable sugars and value-added lignin compounds

BackgroundOrganosolv pretreatment is one of the most efficient methods for delignification and boosting biomass saccharification. As compared to typical ethanol organosolv pretreatments, 1,4-butanediol (BDO) organosolv pretreatment is a high-boiling-point solvent pretreatment, which can generate low pressure in the reactor during high temperature cooking that improves the operation safety. Although several studies showed that organosolv pretreatment can lead to effective delignification and enhancement in glucan hydrolysis, there has been no studies on acid- and alkali-catalyzed BDO pretreatment, as well as their comparison on promoting biomass saccharification and lignin utilization.ResultsIt was shown that BDO organosolv pretreatment was more effective in removing lignin from poplar as compared with typical ethanol organosolv pretreatment under the same pretreatment conditions. HCl-BDO pretreatment with 40 mM acid loading led to 82.04% of original lignin removed from biomass, as compared to the lignin removal of 59.66% in HCl-Ethanol pretreatment. Besides, acid-catalyzed BDO pretreatment was more effective in improving the enzymatic digestibility of poplar than alkali-catalyzed BDO pretreatment. As a result, HCl-BDO with acid loading of 40 mM provided a good enzymatic digestibility of cellulose (91.16%) and the maximum sugar yield of 79.41% from original woody biomass. The linear correlations between physicochemical structure (e.g., fiber swelling, cellulose crystallinity, crystallite size, surface lignin coverage and cellulose accessibility) changes of BDO pretreated poplar and enzymatic hydrolysis were plotted to figure out the main factors that influenced biomass saccharification. Moreover, acid-catalyzed BDO pretreatment mainly brought about the phenolic hydroxyl (PhOH) groups formation in lignin structure, while alkali-catalyzed BDO pretreatment mostly led to the lower molecular weight of lignin.ConclusionsResults indicated that the acid-catalyzed BDO organosolv pretreatment could significantly improve enzymatic digestibility of the highly recalcitrant woody biomass. The great enzymatic hydrolysis of glucan resulted from increased cellulose accessibility, which mostly associated with the higher degree of delignification and hemicellulose solubilization, as well as the more increase in fiber swelling. Besides, lignin was recovered from the organic solvent, which could be used as natural antioxidants. The formation of phenolic hydroxyl groups in lignin structure and the lower molecular weight of lignin contributed to its greater radical scavenging capacity.

SULPHATE COOKING OF THE DEAD SOFT WOOD

The samples of dead wood (the pine, spruce, fir, cedar), damaged in 2017 by the siberian silkmoth and cedar-tree borer is displayed at April 2022 on the Yenisei region of Krasnoyarsk Territory with for sulphate delignification, optimization of the cooking process, estimation of the unbleached cellulose characteristics, determination of the possibility of its use as fibrous semi-finished product of cellulose-paper production. The sulphate cookings are executed in laboratory autoclave under the following constant conditions: hydromodule 4.8; the degree sulfiditiy of the cooking solution 20.8%; the temperature 170 °C. In the course of experiment varied the active alkali consumption (15.5–18.5% from wood mass in unit Na2O) and duration of the isothermal cooking (4.5–6.5 hours). The dependencies of the output and of the cellulose characteristics from these factor is approximated by the regression equations of the second order. Mathematical model of the cookig process obtained such way is used for graphic presentation result in type of the three-dimensional surfaces of the response and for calculation of the best values of the variable cooking factor: consumption active alkali 16.2%; cooking duration 6.1 hour. All samples of the wood was be cooking separately on optimal regime. The cooking results: the cellulose output 37.9–41.3%; the no-cooked part less 1%; degree of the cellulose delignification 23–29 Kаppа unit (the mass part of the lignin 3.38–4.21%); the explosive length 8130– 9250 m; the forcing through resistance 400–490 кPа; tearing resistance 630–870 mmN; break resistance 380–460 bends. The characteristic of the all cellulose samples answer to the mark NS-3. It is noted significant reduction of the cellulose output (on 10–2%) in comparison with cellulose similar degree delignification from sound wood.

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.

Efficient Fractionation and Catalytic Valorization of Raw Biomass in ϵ-Caprolactone and Water.

Efficient fractionation and utilization of the whole biomass is particularly attractive but remains a great challenge, owing to the recalcitrance of biomass. In this study, a simple and efficient approach is developed to obtain high-purity cellulose with a delignification degree of 97.5 % in ϵ-caprolactone and water. FTIR spectroscopy reveals that ϵ-caprolactone and water act in synergy to remove lignin from raw biomass and afford cellulose with clear macrofibrils. A linear positive correlation between the contents of hemicellulose and lignin is observed for the separated cellulose pulp. This mixed solvent exhibits good performance for the removal of lignin from various agricultural and forestry wastes. Moreover, nearly complete transformation of the whole biomass constituents is achieved with Ni-Al catalyst.

A Robust Process to Produce Lignocellulosic Nanofibers from Corn Stover, Reed Canary Grass, and Industrial Hemp.

The use of agricultural waste biomass for nanocellulose production has gained interest due to its environmental and economic benefits compared to conventional bleached pulp feedstock. However, there is still a need to establish robust process technologies that can accommodate the variability of waste feedstocks and to understand the effects of feedstock characteristics on the final nanofiber properties. Here, lignocellulosic nanofibers with unique properties are produced from various waste biomass based on a simple and low-cost process using mild operating conditions. The process robustness is demonstrated by diversifying the feedstock, ranging from food crop waste (corn stover) to invasive grass species (reed canary grass) and industrial lignocellulosic residues (industrial hemp). This comprehensive study provides a thorough examination of the influence of the feedstocks' physico-chemical characteristics on the conversion treatment, including process yield, degree of delignification, effectiveness of nanofibrillation, fiber morphology, surface charge, and density. Results show that nanofibers have been successfully produced from all feedstocks, with minor to no adjustments to process conditions. This work provides a framework for future studies to engineer nanocellulose with specific properties by taking advantage of biomass feedstocks' intrinsic characteristics to enable versatile applications.

Influence of Pretreatment Severity Factor and Hammett Acidity on Softwood Fractionation by an Acidic Protic Ionic Liquid.

The impact of pretreatment severity in the acidic protic ionic liquid (IL) N,N-dimethylbutylammonium hydrogen sulfate, [DMBA][HSO4] using pine softwood was investigated using a modified severity factor that considers the IL solution acidity based on Hammett acidity. A Box-Behnken experimental design was employed to evaluate pretreatment severity with temperature, pretreatment time, and IL concentration as factors and degree of delignification as the response variable. The optimal pretreatment conditions were found to be at 170 °C, 30 min, and 80 wt % IL, which yielded nearly 90% of delignification and 95% of glucose yield in enzymatic saccharification. The modified severity factor showed an improved correlation with the fractionation indicators relative to the classical pretreatment severity factor, indicating that it can better predict the pretreatment outcomes, particularly for delignification and hemicellulose removal. The fate of hemicellulose, its conversion to humins, and its impact on the precipitated lignin properties were also investigated and correlated to the modified pretreatment severity factor. It was found that such parameters alone cannot be used to predict the fate of dissolved hemicellulose sugars in the IL medium. Furthermore, IL acidity greatly impacts the degradation of the dissolved hemicellulose sugars and the formation of humins.

Effects of Severity Levels on Degree of Delignification of Sugarcane Bagasse Using Hydrogen Peroxide and Sodium Hydroxide

Effects of Severity Levels on Degree of Delignification of Sugarcane Bagasse Using Hydrogen Peroxide and Sodium Hydroxide