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Although organosolv processes using high-boiling solvents have been investigated in recent decades for developing novel industrial processes, there are potential benefits of using high-boiling point solvents for traditional sulphate-based cooking processes, both from an industrial perspective and from a laboratory perspective. Using high-boiling solvents, experiments can be done under atmospheric conditions, thus making it easier to continually monitor laboratory experiments and extracting aliquots at desired intervals. Using such a system, alkaline consumption was monitored during impregnation of spruce chips in glycerol media using chemical charges of 1 M NaOH and 0.1 M NaHS, i. e., kraft pulping conditions, and compared to a similar investigation of alkaline consumption in water media using steel autoclaves. The resulting data was fitted to a first order kinetic model, with an apparent activation energy of 22 kJ mol−1 in glycerol media. Finally, a “normal quality pulp” of kappa number 28 and a viscosity of 1113 ml g−1 was successful produced using a cooking process with an impregnation step at 140 °C for 3 h and a cooking step at 160 °C for 4 h. A nuclear magnetic resonance study on the dissolved lignin produced for said experiment showed characteristics typical of other kraft lignins.

Eucalyptus dunnii is cultivated in Uruguay for kraft pulping purposes. However, depending on the growth site, the kraft pulping properties of the wood vary highly, and in some cases, pulping is difficult. Different batches of wood were chemically characterized and the only significant difference related to the pulping properties was the calcium content. The calcium appears to at least partly be present in the form of crystals in the lumen. Kraft pulping experiments on wood with different calcium contents indicated that high calcium led to slower delignification, and higher yield losses. Hexeneuronic acid formation was not significantly affected. Possible mechanistic explanations for these effects are discussed.

Water electrolysis is a promising approach for the sustainable production of hydrogen, however, the unfavorable thermodynamics and sluggish kinetics of oxygen evolution reaction (OER) are associated with high anodic potentials. To lower the required potentials, an effective strategy is proposed to substitute OER with partial oxidation of degradation products of carbohydrate origin from the waste stream of a chemical pulping industry. In this work, two different catalytic materials – PdNi and NiO are investigated comparatively to understand their catalytic performance for the oxidation of carbohydrate alkaline degradation products (CHADs). PdNi can catalyze CHADs with low potential requirements (−0.11 V vs. Hg/HgO at 150 mA cm−2) but is limited to current densities

The development of high-performance electrocatalysts for alcohol oxidation is still a major challenge to use these reactions for sustainable energy applications such as hydrogen production. In addition, understanding the reactivity under different hydrodynamic conditions is essential since the fuel is continuously fed to the anode in practical applications. In this work, the synthesis, characterization and electroactivity of bimetallic PdNi nanocoatings generated by electrodeposition toward the ethanol oxidation reaction (EOR) is described. A catalyst formed by Pd0.91Ni0.09 nanoflowers showed the highest EOR activity and enhanced performance under moderate mass transport rate. Both OH− concentration and hydrodynamics affected the EOR activity and the product selectivity. Acetic acid was the main EOR product, but acetaldehyde formation increased when OH− was limiting or under faster mass transport rates. This study provides novel knowledge to understand the EOR on PdNi catalysts and exposes the importance of evaluating hydrodynamic conditions when developing new electrocatalysts.

Paper grade pulp production across the globe is dominated by the kraft process using different lignocellulosic raw materials. Delignification is achieved around 90% using different chemical treatments. A bottleneck for complete delignification is the presence of residual covalent bonds that prevail between lignin and carbohydrate even after severe chemical pulping and oxygen delignification steps. Different covalent bonds are present in native wood that sustain drastic pulping conditions. In this study, 100% birch wood was used for producing paper grade pulp, and the lignin carbohydrate bonds were analyzed at different stages of the kraft cook. The lignin carbohydrate bonds that were responsible for residual lignin retention in unbleached pulp were compared and analyzed with the original lignin-carbohydrate complex (LCC) bonds in native birch wood. It was shown that lignin remaining after pulping and oxygen delignification was mainly bound to xylan, whereas the lignin bound to glucomannan was for the most part degraded.

Hemicelluloses, a family of heterogeneous polysaccharides with complex molecular structures, constitute a fundamental component of lignocellulosic biomass. However, the contribution of each hemicellulose type to the mechanical properties of secondary plant cell walls remains elusive. Here we homogeneously incorporate different combinations of extracted and purified hemicelluloses (xylans and glucomannans) from softwood and hardwood species into self-assembled networks during cellulose biosynthesis in a bacterial model, without altering the morphology and the crystallinity of the cellulose bundles. These composite hydrogels can be therefore envisioned as models of secondary plant cell walls prior to lignification. The incorporated hemicelluloses exhibit both a rigid phase having close interactions with cellulose, together with a flexible phase contributing to the multiscale architecture of the bacterial cellulose hydrogels. The wood hemicelluloses exhibit distinct biomechanical contributions, with glucomannans increasing the elastic modulus in compression, and xylans contributing to a dramatic increase of the elongation at break under tension. These diverging effects cannot be explained solely from the nature of their direct interactions with cellulose, but can be related to the distinct molecular structure of wood xylans and mannans, the multiphase architecture of the hydrogels and the aggregative effects amongst hemicellulose-coated fibrils. Our study contributes to understanding the specific roles of wood xylans and glucomannans in the biomechanical integrity of secondary cell walls in tension and compression and has significance for the development of lignocellulosic materials with controlled assembly and tailored mechanical properties., Hemicelluloses are an essential constituent of plant cell walls, but the individual biomechanical roles remain elusive. Here the authors report on the interaction of wood hemicellulose with bacterial cellulose during deposition and explore the resultant fibrillar architecture and mechanical properties.

Plant β-mannans are complex heteropolysaccharides that represent an abundant resource from lignocellulosic biomass. The influence of the molecular motifs of plant mannans on the backbone flexibilit...

Fuel wood pellets have the tendency of undergoing self-heating and off-gassing during storage and transportation. Self-heating can lead to spontaneous combustion and cause fires while toxic gasses such as carbon monoxide and some volatile organic compounds released due to off-gassing are a human health and environmental hazard. Previous research suggests that the self-heating and off-gassing of wood pellets are as a result of the oxidation of wood extractives. The aim of this study was to identify the extractives, i.e., fatty and resin acids that are responsible for the emissions of carbon monoxide, carbon dioxide and methane from wood pellets by testing the off-gassing tendencies of pellets produced from synthetic microcrystalline cellulose and different additive oils. The additive oils were intentionally selected to represent different types of wood extractives (mainly fatty and resin acids) and they included: tall oil, pine rosin, linseed oil and coconut oil. The highest mean concentrations of carbon monoxide, carbon dioxide and methane were recorded from cellulose pellets with added linseed oil. The concentrations of carbon monoxide and methane for the other four pellet types were negligible and there was no carbon dioxide emission. Pellets with added linseed oil had high off-gas emissions due to the high content of unsaturated fatty acids compared to other pellet types.

Interaction between xylan and cellulose microfibrils is required to maintain the integrity of secondary cell walls. However, the mechanisms governing their assembly and the effects on cellulose surface polymers are not fully clear. Here, molecular dynamics simulations are used to study xylan adsorption onto hydrated cellulose fibrils. Based on multiple spontaneous adsorption simulations it is shown that an antiparallel orientation is thermodynamically preferred over a parallel one, and that adsorption is accompanied by the formation of regular but orientation-dependent hydrogen bond patterns. Furthermore, xylan adsorption restricts the local dynamics of the adjacent glucose residues in the surface layer to a level of the crystalline core, which is manifested as a three-fold increase in their

Tall oil is a valuable byproduct in chemical pulping of wood, and its fractions have a large spectrum of applications as chemical precursors, detergents, and fuel. High recovery of tall oil is important for the economic and environmental profile of chemical pulp mills. The purpose of this study was to investigate critical parameters of tall oil separation from black liquor. To investigate this in a controlled way, we developed a model test system using a “synthetic” black liquor (active cooking chemicals OH- and HS- ions), a complete process for soap skimming, and determination of recovered tall oil based on solvent extraction and colorimetric analysis, with good reproducibility. We used the developed system to study the effect of the ratio of fatty acids to rosin acids on tall oil separation. When high amounts of rosin acids were present, tall oil recovery was low, while high content of fatty acids above 60% significantly promoted tall oil separation. Therefore, manipulating the content of fatty acids in black liquor before the soap skimming step can significantly affect the tall oil solubility, and hence its separation. The findings open up chemical ways to improve the tall oil yield.

Nickel (oxy)hydroxides (NiOxHy) are promising cost-effective materials that exhibit a fair catalytic activity for the ethanol oxidation reaction (EOR) and could be used for sustainable energy conve ...

The exact mechanism behind the disintegration of chemical pulp fiber into cellulose nanofibers is poorly understood. In this study, samples were subjected to various homogenization cycles, indicating that the mechanism is a stepwise process. In the earlier stages of the mechanical process, a large amount of macrofibrils were created as the larger structures disappeared. Upon mechanical treatment these macrofibrils disappeared despite the increasing yield of cellulose nanofibers. The proposed model expands the understanding of the disintegration pathway and may provide additional insight as to how wood cells are converted into microfibrils.

Biomass electro-oxidation is a promising approach for the sustainable generation of H2 by electrolysis with simultaneous synthesis of value-added chemicals. In this work, the electro-oxidation of two structurally different organic hydroxyacids, lactic acid and gluconic acid, was studied comparatively to understand how the chemical structure of the hydroxyacid affects the electrochemical reactivity under various conditions. It was concluded that hydroxyacids such as gluconic acid, with a considerable density of C-OH groups, are highly reactive and promising for the sustainable generation of H2 by electrolysis at low potentials and high conversion rates (less than -0.15 V vs. Hg/HgO at 400 mA cm-2 ) but with low selectivity to specific final products. In contrast, the lower reactivity of lactic acid did not enable H2 generation at very high conversion rates (

A novel method exploiting the in situ reactivation of a PdNi catalyst to enhance the electro-oxidation of alcohols is reported. The periodic regeneration of the catalyst surface leads to significant gains in terms of conversion rate, energy requirements and stability compared to the conventional potentiostatic method.

Off-gassing and self-heating are the major challenges when it comes to transportation and storage of wood pellets. The heat generated due to self-heating poses a fire risk while off-gassing of toxic gasses such as carbon monoxide (CO) and some volatile organic compounds (VOCs) is an environmental and human health risk. With the increase in production volumes of wood pellets which has subsequently increased the amounts of wood pellets in transportation and storage, there is need to find lasting solutions to off-gassing and self-heating of wood pellets. The objective of this study was to test the off-gassing abilities of Scots pine wood pellets produced from sawdust with varying amounts of extractives. The aim is to come up with raw material pre-treatment measures so as to produce wood pellets that are not liable to off-gassing. Six (6) types of sawdust raw materials namely; fresh pine sawdust (FPS), stored pine sawdust (SPS), sawdust plus pine rosin (PRS), sawdust plus linseed oil (LOS), sawdust plus tall oil (TOS) and acetone extracted sawdust (AES) were used to produce the pellets. The produced pellets were then subjected to off-gassing tests under controlled conditions using the ECOM J2KN analyser. The concentrations of carbon monoxide, carbon dioxide and methane increased with storage time but slowed down towards the end of the nine days test period. The formation of these gasses were largely dependent on the type of extractives present in the raw material and not the total extractive content. The formation of methane started later than the other gases and coincided with the time when residual oxygen was depleted.

To investigate the dispersibility of dried cellulose nanofibers (CNFs), various additions (glycerol, octanol, glycol, and sodium perchlorate) were added to CNFs prior to drying. Glycerol was the only species to show any significant effect on re-dispersibility. The sedimentation was slower, and the transmittance of the solution was comparable to that of its undried counterpart. Increasing the amount of glycerol showed a clear trend with regard to dispersibility. The mechanical properties of films were maintained for samples that were dried and redispersed in the presence of glycerol.

An ecofriendly approach for the synthesis of plastic biomaterials based on renewable materials suitable for 3D printing application or other applications has been developed. The material was prepared from native (microcrystalline) or amorphous cellulose, citric acid, and glycerol or ethylene glycol, by a pretreatment at 40 °C and a curing at 175 °C for 1 h. The results showed that tensile properties and the water absorption level of the material were acceptable. The highest strain at break (14%) was obtained from materials made of 10% amorphous cellulose with 90% glycerol/citric acid. It had a maximum stress at 37 MPa. Moreover, materials were without ash content. Possible applications of the material in 3D-printers were discussed. In addition, application of mechanical pulp and wood powder into novel plastic material production was discussed. Foaming during curing might be a problem for this type of material, but this can be avoided by using amorphous cellulose in the recipe.

In this paper, we explore xyloglucan adsorption to cellulose nanofibers as a method for the evaluation of their quality (i. e., the degree of disintegration) and the accessible surface area in the wet state and at low ionic strength. This method was shown to be capable of estimating the surface areas of 14 different cellulose nanofiber qualities from both hardwood and softwood with different pretreatments, including enzymatic hydrolysis using a monocomponent endoglucanase, TEMPO-mediated oxidation, and carboxymethylation. The cellulose surface measured using this method showed a correlation with the degree of disintegration expressed as transmittance for different concentrations of xyloglucan.

The hemicellulose xyloglucan can be utilized to measure exposed cellulose surfaces for pulp fibers. This was shown by correlating a refining series with the adsorbed amount of xyloglucan, and by swelling cellulose fibers to various degrees by increasing the charge density. The method is specific to cellulose and could be used to quantify refining or to determine hornification.

The presence of covalent bonds between lignin and polysaccharides was investigated in dissolving pulps made with one-stage and two-stage acidic sulfite pulping for 100% pine heartwood raw material. ...

Galactoglucomannan (GGM) from sprucewas studied with respect to the degradation behavior inalkaline solution. Three reference systems includinggalactomannan from locust bean gum, glucomannanfrom ko ...

In a recent study, it was suggested that there could be direct associations between cellulose and lignin in mild alkaline cooked pulps. The observation was based on studies showing that the molecul ...

Xylan is tightly associated with cellulose and lignin in secondary plant cell walls, contributing to its rigidity and structural integrity in vascular plants. However, the molecular features and the nanoscale forces that control the interactions among cellulose microfibrils, hemicelluloses, and lignin are still not well understood. Here, we combine comprehensive mass spectrometric glycan sequencing and molecular dynamics simulations to elucidate the substitution pattern in softwood xylans and to investigate the effect of distinct intramolecular motifs on xylan conformation and on the interaction with cellulose surfaces in Norway spruce (Picea abies). We confirm the presence of motifs with evenly spaced glycosyl decorations on the xylan backbone, together with minor motifs with consecutive glucuronation. These domains are differently enriched in xylan fractions extracted by alkali and subcritical water, which indicates their preferential positioning in the secondary plant cell wall ultrastructure. The flexibility of the 3-fold screw conformation of xylan in solution is enhanced by the presence of arabinofuranosyl decorations. Additionally, molecular dynamic simulations suggest that the glycosyl substitutions in xylan are not only sterically tolerated by the cellulose surfaces but that they increase the affinity for cellulose and favor the stabilization of the 2-fold screw conformation. This effect is more significant for the hydrophobic surface compared with the hydrophilic ones, which demonstrates the importance of nonpolar driving forces on the structural integrity of secondary plant cell walls. These novel molecular insights contribute to an improved understanding of the supramolecular architecture of plant secondary cell walls and have fundamental implications for overcoming lignocellulose recalcitrance and for the design of advanced wood-based materials.

Several different methods for the extraction, separation, and purification of wood constituents were combined in this work as a unified process with the purpose of achieving a high overall efficiency of material extraction and utilization. This study aimed to present a laboratory-scale demonstrator biorefinery that illustrated how the different wood constituents could be separated from the wood matrix for later use in the production of new bio-based materials and chemicals by combining several approaches. This study builds on several publications and ongoing activities within the Wallenberg Wood Science Center (WWSC) in Sweden on the theme “From wood to material components.” Combining the approaches developed in these WWSC projects – including mild steam explosion, membrane and chromatographic separation, enzymatic treatment and leaching, ionic liquid extraction, and fractionation together with Kraft pulping – formed an outline for a complete materials-biorefinery. The process steps involved were tested as integral steps in a linked process. The scale of operations ranged from the kilogram-scale to the gram-scale. The feasibility and efficiency of these process steps in a biorefinery system were assessed, based on the data, beginning with whole wood.

Lignin has a very complex structure, and this is partly due to the monomers being connected by many different types of covalent bonds. Furthermore, there are multiple covalent bonds between lignin and polysaccharides in wood, and it is known that the structure of lignin covalently bound to the hemicellulose xylan is different to lignin bound to the hemicellulose glucomannan. Here, synthetic lignin (DHP) is synthesized at different pH and it is shown that lignin made at lower pH has a structure more similar to the lignin bound to xylan, i.e., having higher relative content of β-O-4 ethers. It is hypothesized that xylan due to its carboxylic acids forms a locally lower pH and thus “direct” the lignin structure to have more β-O-4 ethers. The biological significance of these results is discussed.

This work reveals the structural variations of cellulose nanofibers (CNF) prepared from different cellulose sources, including softwood (Picea abies), hardwood (Eucalyptus grandis × E. urophylla), and tunicate (Ciona intestinalis), using different preparation processes and their correlations to the formation and performance of the films prepared from the CNF. Here, the CNF are prepared from wood chemical pulps and tunicate isolated cellulose by an identical homogenization treatment subsequent to either an enzymatic hydrolysis or a 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation. They show a large structural diversity in terms of chemical, morphological, and crystalline structure. Among others, the tunicate CNF consist of purer cellulose and have a degree of polymerization higher than that of wood CNF. Introduction of surface charges via the TEMPO-mediated oxidation is found to have significant impacts on the structure, morphology, optical, mechanical, thermal, and hydrophobic properties of the prepared films. For example, the film density is closely related to the charge density of the used CNF, and the tensile stress of the films is correlated to the crystallinity index of the CNF. In turn, the CNF structure is determined by the cellulose sources and the preparation processes. This study provides useful information and knowledge for understanding the importance of the raw material for the quality of CNF for various types of applications.

Lignin extracted from trees is one of the most abundant biopolymers on Earth. Quinone, a substructure in lignin, can be used for energy storage via reversible redox reactions through absorbing and releasing electrons and protons. However, these efforts have encountered hindrances, such as short life cycle, low cycling efficiency, and a high self-discharge rate. All of these issues are related to electrode dissolution by electrolyte solvents and the insulating nature of lignin. Addressing these critical challenges, for the first time, we use a reconfigurable and hierarchical graphene cage to capture the lignin by mimicking the prey-trapping of venus flytraps. The reconfigurable graphene confines the lignin within the electrode to prevent dissolution, while acting as a three-dimensional current collector to provide efficient electron transport pathways during the electrochemical reaction. This bioinspired design enables the best cycling performance of lignin reported so far at 88% capacitance retention for ...

Hemicelluloses as major components of plant cell walls are acetylated to different extents. The biologicalfunctions of acetylation are not completely understood but suggested that one reason is to ...

With the arising of global climate change and resource shortage, in recent years, increased attention has been paid to environmentally friendly materials. Trees are sustainable and renewable materials, which give us shelter and oxygen and remove carbon dioxide from the atmosphere. Trees are a primary resource that human society depends upon every day, for example, homes, heating, furniture, and aircraft. Wood from trees gives us paper, cardboard, and medical supplies, thus impacting our homes, school, work, and play. All of the above-mentioned applications have been well developed over the past thousands of years. However, trees and wood have much more to offer us as advanced materials, impacting emerging high-tech fields, such as bioengineering, flexible electronics, and clean energy. Wood naturally has a hierarchical structure, composed of well-oriented microfibers and tracheids for water, ion, and oxygen transportation during metabolism. At higher magnification, the walls of fiber cells have an interesting morphology-a distinctly mesoporous structure. Moreover, the walls of fiber cells are composed of thousands of fibers (or macrofibrils) oriented in a similar angle. Nanofibrils and nanocrystals can be further liberated from macrofibrils by mechanical, chemical, and enzymatic methods. The obtained nanocellulose has unique optical, mechanical, and barrier properties and is an excellent candidate for chemical modification and reconfiguration. Wood is naturally a composite material, comprised of cellulose, hemicellulose, and lignin. Wood is sustainable, earth abundant, strong, biodegradable, biocompatible, and chemically accessible for modification; more importantly, multiscale natural fibers from wood have unique optical properties applicable to different kinds of optoelectronics and photonic devices. Today, the materials derived from wood are ready to be explored for applications in new technology areas, such as electronics, biomedical devices, and energy. The goal of this study is to review the fundamental structures and chemistries of wood and wood-derived materials, which are essential for a wide range of existing and new enabling technologies. The scope of the review covers multiscale materials and assemblies of cellulose, hemicellulose, and lignin as well as other biomaterials derived from wood, in regard to their major emerging applications. Structure-properties-application relationships will be investigated in detail. Understanding the fundamental properties of these structures is crucial for designing and manufacturing products for emerging applications. Today, a more holistic understanding of the interplay between the structure, chemistry, and performance of wood and wood-derived materials is advancing historical applications of these materials. This new level of understanding also enables a myriad of new and exciting applications, which motivate this review. There are excellent reviews already on the classical topic of woody materials, and some recent reviews also cover new understanding of these materials as well as potential applications. This review will focus on the uniqueness of woody materials for three critical applications: green electronics, biological devices, and energy storage and bioenergy.

The characteristics of two novel types of technical lignin, namely Ecohelix (EH) and CleanFlow black lignin (CFBL), isolated from two different pulping process side streams, were analyzed. EH and CFBL were analyzed in terms of general composition, chemical functionalities, molar mass distribution, and thermal stability. For comparison, two relevant types of commercially available lignosulfonate and kraft lignin were used. The results showed that EH contains a large amount of sulfonated lignin, together with carbohydrates and ash. As such, it can be considered a lignin-carbohydrate hybrid molecule. CFBL was found to contain 91.5% Klason lignin and the lowest amount of carbohydrates (0.3%). EH showed the highest content of aliphatic OH groups (5.44 mmol/g) and CFBL a high content of phenols (4.73 mmol/g). EH had a molecular weight of 31.4 kDa and a sufficient thermal stability. CFBL had the lowest molecular weight (Mw = 2.0 kDa) and thermal stability of all kraft lignins analyzed in this study. These properties highlighted that EH is a suitable building block for material development and that CFBL is a promising material for the production of biofuel and biochemicals.

A series of optically transparent composites were made by using tunicate cellulose membranes, in which the naturally organized cellulose microfibrillar network structure of tunicate tunics was preserved and used as the template and a solution of glycerol and citric acid at different molar ratios was used as the matrix. Polymerization through ester bond formation occurred at elevated temperatures without any catalyst, and water was released as the only byproduct. The obtained composites had a uniform and dense structure. Thus, the produced glycerol citrate polyester improved the transparency of the tunicate cellulose membrane while the cellulose membrane provided rigidity and strength to the prepared composite. The interaction between cellulose and polyester afforded the composites high thermal stability. Additionally, the composites were optically transparent and their shape, strength, and flexibility were adjustable by varying the formulation and reaction conditions. These composites of cellulose, glycerol, and citric acid are renewable and biocompatible and have many potential applications as structural materials in packaging, flexible displays, and solar cells.