Liquid Lignin Research Articles

Solvent Fractionation and Depolymerization Provide Liquid Lignin Fractions Exploited as Bio-based Aromatic Building Blocks in Epoxies

In the context of a green transition, alternatives to fossil-based aromatic compounds have to be implemented. In this study, the combination of sequential solvent fractionation followed by depolymerization via catalytic hydrogenolysis of lignin led to liquid oligomeric lignin structures with chemical properties governed by the choice of lignin soluble fraction. Lignin species of increasing molecular weight (MW) were obtained with MW reduction up to 72% compared to the parent lignin, with a corresponding increase in total hydroxyl content up to 18% obtained through cleavage of lignin ether bonds. Hydrogenolysis led to lignin depolymerization oils comprising macromolecular lignin fragments and app. 15–18 wt % lignin monomers, resulting in a liquid product mixture. The lignin species were epoxidized to show their potential as a bio-based aromatic substitute to fossil-based bisphenol A. Liquid epoxy resins were obtained with viscosities between 2 × 103 and 4 × 105 Pa·s, which after curing resulted in thermoset networks with Young’s moduli between 0.9 and 1.4 GPa depending on the lignin fraction. Optimal viscosity to mechanical performance was obtained for ethyl acetate and ethanol solvent fractionated and depolymerized lignins as lower viscosity allows for reduced use of volatile organics.

Maximizing yield of liquid-lignin from membrane filtration retentate of kraft black liquor

Removal of lignin from kraft pulping black liquor has the potential to increase pulp production, and at the same time lignin can serve as raw material for renewable fuels. There are well-known challenges associated with the outtake of lignin from kraft black liquor. Examples of such challenges are acid consumption and effects on the Na/S balance in the pulp mill, which can be decreased by a new process concept combining membrane filtration and liquid-lignin separation. In this study, we investigated the yield of liquid-lignin in separation from kraft black liquor retentate, specifically concerning how it was influenced by the presence of xylose and galactoglucomannan. For example, the liquid lignin yield after carbon dioxide separation decreased from 89.3 % to 85.2 % and 86.1 % with the addition of 20 g/L xylose and galactoglucomannan, respectively. The results showed that the yield of liquid-lignin decreased with an increasing amount of sugar added. Similarly to previous research, our results showed an improvement of liquid-lignin yield associated with a decrease in the content of sugars in cases of heat treatment prior to separation.We suggest a new explanation for the interaction between lignin and hemicellulose, namely that the interactions occur at a molecular level, with lignin in solution, and that these interactions possibly involve the formation of covalent lignin-carbohydrate bonds. This makes the lignin more polar and less prone to form a liquid-lignin phase.

Study on extraction of cotton stalk lignin by different methods and its antioxidant property in polypropylene

ABSTRACT In this paper, ionic liquid method and ultrasound-assisted ionic liquid method were used to extract lignin and the effects of various factors on the extraction of lignin were investigated. The properties and antioxidant properties of lignin were studied. The lignin extraction rates of the two methods were 93.60% and 94.01%, respectively. On this basis, the oxidation resistance and stability of lignin in polypropylene were studied, and the added value of lignin was increased. It was shown that the lignin extracted by two different methods had a certain antioxidant effect, and the ultrasonic assisted ionic liquid lignin had the best antioxidant effect.

Quantitative structures and thermal properties of Miscanthus × giganteus lignin after alcoholamine-based ionic liquid pretreatment

Alcoholamine-based ionic liquid (IL) pretreatment has been potential due to low cost (∼$1.0/kg) and efficient delignification. However, valuable exploration of lignin during this pretreatment has not been systematically studied and this hinders its further commercialized application. In this study, the effects of mild and efficient ethanolamine acetate [EOA][OAc] pretreatment on the structural and thermal feature of Miscanthus × giganteus (M×g) lignin were evaluated in detail. The ionic liquid lignin (ILL), and residual-enzymatic hydrolysis-mild acidolysis lignin (R-EMAL) were compared with the original-enzymatic hydrolysis-mild acidolysis lignin (O-EMAL). Results determined that Guaiacyl (G) was the predominant unit in all the lignins. As compared to O-EMAL, ILL had higher yield, high purity, less β-O-4 ether linkages, and more COOH contents as well as a higher thermal stability owing to formation of slightly condensed structures. Additionally, depolymerization of the lignin occurred as the reduction of the molecular weight, and cleavage of β-O-4 ether linkages. Furthermore, R-EMAL was similar to O-EMAL as approximative β-O-4 ether linkages, molecular weight and thermal stability. The structural elucidation of M×g lignin could provide a good theoretical basis for economic improvement of the alcoholamine-based biorefinery and efficient conversion of lignocellulose to high value-added lignin-based products.

Ionic Liquid Lignosulfonate: Dispersant and Binder for Preparation of Biocomposite Materials

AbstractIonic liquid lignins are prepared from sodium lignosulfonate by a cation exchange reaction and display glass transition temperatures as low as −13 °C. Diethyleneglycol‐functionalized protic cations inhibit lignin aggregation to produce a free‐flowing “ionic liquid lignin”, despite it being a high‐molecular‐weight polyelectrolyte. Through this approach, the properties of both lignin and ionic liquids are combined to create a dispersant and binder for cellulose+gluten mixtures to produce small microphases. Biocomposite testing pieces are produced by hot‐pressing this mixture, yielding a material with fewer defects and improved toughness in comparison to other lignins. The use of unmodified lignosulfonate, acetylated lignosulfonate, or free ionic liquid for similar materials production yields poorer substances because of their inability to maximize interfacial contact and complexation with cellulose and proteins.

Ionic Liquid Lignosulfonate: Dispersant and Binder for Preparation of Biocomposite Materials.

Ionic liquid lignins are prepared from sodium lignosulfonate by a cation exchange reaction and display glass transition temperatures as low as −13 °C. Diethyleneglycol‐functionalized protic cations inhibit lignin aggregation to produce a free‐flowing “ionic liquid lignin”, despite it being a high‐molecular‐weight polyelectrolyte. Through this approach, the properties of both lignin and ionic liquids are combined to create a dispersant and binder for cellulose+gluten mixtures to produce small microphases. Biocomposite testing pieces are produced by hot‐pressing this mixture, yielding a material with fewer defects and improved toughness in comparison to other lignins. The use of unmodified lignosulfonate, acetylated lignosulfonate, or free ionic liquid for similar materials production yields poorer substances because of their inability to maximize interfacial contact and complexation with cellulose and proteins.

Detritus to Functional Auxiliary: Twin Properties Polymer from Woody Biomass for Leather Post-Tanning Application

Economic feasibility and dual functionalities are contemplated as the most substantial parameters for polymers applicable in leather industries. In this work, we have identified an easy step to utilize black liquor (paper and pulp industrial waste) as a dual functional auxiliary in the post-tanning stage of leather processing. By a simple acidification method, soluble lignin (liquid lignin) was separated, and the percentage of acid input was optimized. A detailed characterization of liquid lignin products emphasized their improved functionality, better organic content, and appropriate particle size and surface potential. The presence of more hydroxyl groups with larger aromatic rings in liquid lignin results in improved leather quality with high surface smoothness and filling. In order to determine the dyeing property influenced by liquid lignin, three types of dyes were used as a dyeing agent. Along with the retanning ability, lignin was able to influence the dyeing greatly by good adsorption with minima...

Liquid Lignin from the SLRPTM Process: The Effect of Processing Conditions and Black-Liquor Properties

CO2 acidification of Kraft black liquors was performed at temperatures of 100–150°C and pressures of 5–8 bar in an investigation of the SLRPTM process. At these conditions, a highly hydrated, lignin-rich liquid (vs. the usual solid) separated out to form a new phase. The solids content/ionic strength of the starting black liquor was found to be a key variable for controlling the bulk and molecular properties of the „liquid-lignin” (LL) phase. For example, black liquors of lower ionic strengths (20% solids) produced LLs with lower ash contents and higher molecular weights, albeit in lower yields. In contrast, higher ionic strengths/solids content (40%) produced LLs in higher yields with higher aromatic and aliphatic hydroxyl contents. Temperature effects were significant only at the highest levels. The degree of hydration of the LL phase was found to be a useful measure of the water available for hydration of ionized/polarizable groups in lignin.

Temperature Effects on the Molecular Properties of Liquid Lignin Recovered from Kraft Black Liquor

The effect of temperature on the molecular properties of a “liquid-lignin” phase recovered from Kraft black liquor via CO2 acidification at elevated temperatures was investigated. For softwood black liquors, up to a 4-fold increase in the molecular weight (mol wt) of the recovered liquid-lignin phase was observed as the acidification temperature was increased from 100 to 150 °C. Thus, experiments were carried out in which the CO2-acidification steps of preheating, acidification, and phase separation were decoupled from each other in order to elucidate the mechanisms for the observed changes in molecular weight. Results indicate that some lignin cleavage and a corresponding decrease in molecular weight occur during the black-liquor preheating step. However, a significant net increase in molecular weight occurs after the lignin has phase-separated from the black liquor in the form of a new, denser liquid phase, pointing to condensation reactions as the most likely cause. Minimal changes in lignin aromatic c...

Environmental assessment of chemical products from a Norwegian biorefinery

To mitigate climate change and to ensure energy security, society is searching for alternatives to fossil fuels. Biomass is an interesting renewable resource, because it can be used both as energy and as feedstock for material and chemical production. The aim of this article is to present the environmental impacts associated with products from a biorefinery in Norway (Borregaard). More specifically, the article shows results from studies on the products ethanol 96%, ethanol 99%, cellulose, liquid lignin, lignin powder and vanillin, and identifies the processes which contribute most in each impact category and product. Comparative emissions are also shown for at least one product alternative. The study has been carried out using the life cycle assessment method from “cradle to gate”. The functional unit is 1 tonne product for cellulose, lignin and vanillin and 1 m3 product for ethanol. All of the products are based on the same raw materials (timber and wood chips). The infrastructure of the biorefinery has been included. The study has, as far as possible, avoided allocation by analysing and modelling the processes at a detailed level. Where necessary, energy allocation, using dry weight energy content, has been applied. Climate change, acidification, eutrophication, photochemical ozone creation, ozone depletion and cumulative energy demand have been selected as environmental impact categories. Different processes relating to the biorefinery have significance for the various environmental impact categories. This has made it difficult to single out the processes to be studied further. Oil combustion is the most important process in relation to climate change. Infrastructure is not important for either impact category. The global warming potential for bioethanol from Borregaard is in the lower range when compared with earlier studies. To conclude, this article demonstrates that the biofuel under study is, even at worst, comparable to that produced using other bioethanol production processes. The other products are also substitutes for fossil derived chemicals, but as the available literature lacks data for such chemicals, the environmental profiles for these have not been compared.

Structural features and thermal degradation properties of various lignin macromolecules obtained from poplar wood (Populus albaglandulosa)

Four different lignins obtained from poplar wood (milled wood lignin: ML, organosolv lignin: OL, ionic liquid lignin: IL and Klason lignin: KL) were subjected to several types of chemical/thermal analyses to compare their structural features and thermal decomposition properties. The ML, OL, IL and KL yield from poplar wood was 5.5, 3.9, 5.8, 19.5 wt%, respectively. Functional group analysis revealed that during the OL and KL extraction processes, the condensation reaction involved with phenolic hydroxyl groups of lignins significantly prevailed, which led to a highly condensed OL and KL structure. Thermogravimetric analysis (TGA) results showed that OL and KL thermal stability was much higher than that of ML and IL. The derivatization followed by reductive cleavage (DFRC) data showed that the thermal stability was highly associated with the frequency of arylglycerol-β-aryl ether (β-O-4) linkages in the lignin polymers. Pyrolysis-GC/MS (Py-GC/MS) analysis confirmed that acetic acid and several types of phenolic compounds were the main lignin pyrolysis products. The maximum sum of ML (13.8 wt%), OL (9.9 wt%) and IL (11.8 wt%) pyrolysis products was obtained at the pyrolysis temperature of 600 °C, whereas KL (1.6 wt%) was significantly lower due to its high thermal stability and condensation degree. The S- and G-type pyrolysis products (S/G) ratio varied from 1.61 to 1.93 for ML, 2.28 to 5.28 for OL, 2.06 to 2.86 for IL and 1.40 to 2.20 for KL, depending on the pyrolysis temperature, which ranged between 400 °C and 700 °C.

Quantitative Structures and Thermal Properties of Birch Lignins after Ionic Liquid Pretreatment

The use of ionic liquid (IL) in biomass pretreatment has received considerable attention recently because of its effectiveness in decreasing biomass recalcitrance to subsequent enzymatic hydrolysis. To understand the structural changes of lignin after pretreatment and enzymatic hydrolysis process, ionic liquid lignin (ILL) and subsequent residual lignin (RL) were sequentially isolated from ball-milled birch wood. The quantitative structural features of ILL and RL were compared with the corresponding cellulolytic enzyme lignin (CEL) by nondestructive techniques (e.g., FTIR, GPC, quantitative (13)C, 2D and (31)P NMR). The IL pretreatment caused structural modifications of lignin (cleavage of β-O-4 ether linkages and formation of condensed structures). In addition, lignin fragments with lower S/G ratios were initially extracted, whereas the subsequently extracted lignin is rich in syringyl unit. Moreover, the maximum decomposition temperature (T(M)) was increased in the order ILL < RL < CEL, which was related to the corresponding β-O-4 ether linkage content and molecular weight (M(w)). On the basis of the results observed, a possible separation mechanism of IL lignin was proposed.

이온성액체(1-ethyl-3-methylimidazolium acetate)로 추출한 리기다소나무(pitch pine) 리그닌의 화학·구조 특성

1-Ethyl-3-methylimidazolium acetate known as efficient biomass pretreatment reagent was used for the extraction of lignin from rigida pine wood (pitch pine), which was called to ionic liquid lignin (ILL), and chemical structural features of ILL were compared with the corresponding milled wood lignin (MWL). The amounts of phenolic hydroxyl groups (Phe-OH) was determined to 10.0% for ILL and 7.2% for MWL, respectively, where those of methoxyl groups (OMe) were 4.9% for ILL and 11.0% for MWL, respectively. The weight average molecular weight (Mw) of ILL (3,995) were determined to ca. 1/2 of that of MWL (8,438) and polydispersity index (PDI: Mw/Mn) suggested that the lignin fragments were more uniform in the ILL (PDI 1.36) than in the MWL (PDI 2.64). The temperature (Tm) corresponding to maximum decomposition rate (Vm) of ILL () was ca. lower than that of MWL (), suggesting that ILL was thermally unstable than MWL, as evidence from the lower Tm for ILL. Moreover, the structural characteristics of ILL and MWL were confirmed by spectroscopic analyses (FT-IR and -NMR), and these results indicated ionic liquid (1-ethyl-3-methylimidazolium acetate) was chemically or physically bound to ILL.

Structural features of lignin macromolecules extracted with ionic liquid from poplar wood

1-Ethyl-3-methylimidazolium acetate ([Emim][CH3COO]) was used for the extraction of lignin from poplar wood (Populus albaglandulosa), which was called to ionic liquid lignin (ILL) and structural features of ILL were compared with the corresponding milled wood lignin (MWL). Yields of ILL and MWL were 5.8±0.3% and 4.4±0.4%, respectively. The maximum decomposition rate (VM) and temperature (TM) corresponding to VM were 0.25%/°C and 308.2°C for ILL and 0.30%/°C and 381.3°C for MWL. The amounts of functional groups (OMe and phenolic OH) appeared to be similar for both lignins; approximately 15.5% and 6.7% for ILL and 14.4% and 6.3% for MWL. However, the weight average molecular weight (Mw) of ILL (6347Da) was determined to be 2/3-fold of that of MWL (10,002Da) and polydispersity index (PDI: Mw/Mn) suggested that the lignin fragments were more uniform in the ILL (PDI 1.62) than in the MWL (PDI 2.64).

DSC study on the effect of cure reagents on the lignin base epoxy cure reaction

AbstractThe cure reactions of liquid lignin base epoxy resin (LEPL) with three different curing agents, viz., methylhexahydrophthalic anhydride, maleic anhydride, and 2‐methyl‐4‐methylimidazole (EMI‐2,4), were investigated by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry. Cure kinetics was evaluated using the multiple heating rate Kissinger method. The reactivities of the three curing agents were compared based on kinetics results obtained by DSC. FTIR spectra of these curing systems were also studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Comparative study on the curing kinetics and mechanism of a lignin-based-epoxy/anhydride resin system

Curing kinetics and mechanism of liquid lignin based epoxy resin (LEPL)–maleic anhydride (MA) system accelerated with benzyldimethylamine (BDMA) were studied by Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). In order to investigate the difference in the curing process, heating FTIR was used to study the change of the functional group. Complete consumption of the epoxides has been observed after the heating temperature was higher than 110°C. E constant method and E variable method, to study the dynamic DSC curves, were deduced by assuming a constant and a variable activation energy, respectively. With E constant method, the cure reaction activation energy E, the frequency factor A and overall order of reaction n+m are calculated to be 59.68kJmol−1, e20.6 and 1.462, respectively. With E variable method, E is proved to decrease initially, and then increases as the cure reaction proceeds. The value of E spans from 60.16 to 87.80kJmol−1. With the E constant method, E variable method and heating FTIR spectra used together, we can have a comprehensive and profound understanding of the cure reactions of the LEPL–MA system.

Effects of Citrus Molasses Distillers Solubles and Molasses on Rumen Parameters and Lactation

Effects of dietary citrus molasses distillers solubles (0, 6, 12, and 18% of DM) on diet digestibility and ruminal parameters were studied with four fistulated Holstein cows fed each diet in Latin square sequence. Diets were 25% cottonseed hulls with solubles substituted for corn. Dry matter and organic matter digestibilities were increased curvilinearly with peak at 6%. Crude protein digestibility was depressed linearly and ADF curvilinearly with added solubles. Ruminal acetic acid proportion increased linearly and propionic acid decreased curvilinearly. Change in butyric acid was small with 0, 6, and 12% solubles but it increased dramatically with 18%. In a 36-cow (107 cow-period) lactation experiment with corn silage-based and cottonseed hull-based diets (0, 3, 6, and 9% solubles) milk yield increased; the diet containing 6% solubles gave highest production. We compared cane molasses (3 and 6%), liquid hemicellulose extract (3%, Masonex), and liquid lignin sulfonate (3%, Flambeau) added to cottonseed hull diets. Linear increases in milk yield and FCM were obtained with cane molasses; Flambeau and Masonex effects on production were not different from control. With diets and amounts used in these experiments, citrus molasses solubles and cane molasses each at up to 6% of DM nutritionally were superior to corn.