Ethanol Lignin Research Articles

Calorific Power Improvement of Wood by Heat Treatment and Its Relation to Chemical Composition

Chemical composition influences the calorific power of wood, mainly due to the calorific power of structural compounds and extractives. Heat treatment changes the chemical composition of treated wood. This work studies the relationship between chemical composition and calorific power improvement by heat treatment. Samples were heat-treated by the ThermoWood process ® for 1 h and 2 h. High heating value (HHV) and chemical composition; lignin, cellulose, hemicelluloses and extractives in dichloromethane, ethanol, and water were determined. The HHV of untreated wood ranged between 18.54–19.92 MJ/kg and increased with heat treatment for all the tested species. A positive linear correlation was found between HHV and Klason lignin (R2 = 0.60). A negative trend was observed for holocellulose, cellulose, and hemicelluloses content against HHV, but with low determination coefficients for linear regression. The best adjust for polysaccharides was found for hemicelluloses content. A positive correlation could be found for dichloromethane extractives (R2 = 0.04). The same was obtained in relation to ethanol extractives with R2 = 0.20. For water and total extractives, no clear positive or negative trends could be achieved. The results showed that the HHV of wood increased with heat treatment and that this increase was mainly due to the increase in lignin content.

Depolymerization of Pine Ethanol Lignin in the Medium of Supercritical Ethanol in the Presence of Catalysts NiCu/SiO₂ and NiCuMo/SiO₂

The regularities of thermocatalytic transformation of pine ethanol lignin in supercritical ethanol in the presence of catalysts NiCu/SiO₂ and NiCuMo/SiO2 in the temperature range 250–400 °C were established. The composition and structure of ethanol lignin, liquid and solid products of its conversion were studied by methods of elemental analysis and gel-permeating chromatography (GPC). The composition of gaseous products – by method of gas chromatography. At the process temperature of 250 °C the catalysts do not have a significant effect on conversion of ethanol lignin. The maximal yield of liquid products (83.5 wt. %) was obtained at temperature 300 °C in the presence of catalyst NiCuMo/SiO₂ containing 8.8 wt. % of molybdenum. At temperature 350 °C NiCu/SiO₂ and NiCuMo/SiO2 catalysts contribute to the almost complete conversion of ethanol lignin into liquid and gaseous products, and the yield of solid products does not exceed 1 wt. %. In liquid products of catalytic conversion there is a decrease in the atomic ratio of O/C and the increase of H/C atomic ratio as compared to initial ethanol lignin due to catalytic intensification of reactions of deoxygenation and hydrogenation of lignin and products of its depolymerization. According to GPC data on the curves of molecular mass distribution (MMD) of liquid products of thermocatalytic conversion of ethanol lignin at 300 °C there are peaks with highs at 160 and 380 Da, probably related to guiacyle monomers and dimmers, respectively. From the comparison of MMD of liquid products obtained by ethanol lignin depolymerization at 300 °C over catalysts NiCu/SiO₂ and NiCuMo/SiO₂ it follows, that the introduction of molybdenum in the catalyst promotes the formation of monomeric guaiacyl products

Numerical Optimization of the Abies Ethanol Lignin Sulfation Process with Sulfamic Acid in 1,4-Dioxane Medium in the Presence of Urea

The process of abies ethanol lignin sulfation with sulfamic acid in 1,4-dioxane medium in the presence of urea was optimized by calculation methods. The influence of such factors, as the ratio of lignin/sulfating complex (L/SC), temperature and time of the sulfation process on the sulfur content in the resulting sulfated ethanol lignin and its yield, has been established. The variance analysis of the obtained mathematical models testifies their good predictive properties. The optimal conditions of abies ethanol lignin sulfation process, which provide the formation of water-soluble sulfated lignin with a high yield (to 100 % wt.) and sulfur content (up to 7.9 % wt.), have been established. They are: temperature of 95-100 °C, the ratio L/SC 1:2,3-1:2:9 and the time of the process 119-137 minutes

Catalytic hydrogenolysis of native and organosolv lignins of aspen wood to liquid products in supercritical ethanol medium

Catalytic hydrogenolysis in the medium of supercritical organic solvents is a promising way of wood lignins depolymerization into liquid products.In this study, for the first time, the catalytic properties of bifunctional catalysts Ru/C, Pt/ZrO2, NiCuMo/SiO2, containing nanosized metal particles on acidic groups are compared in the processes of aspen wood and ethanol lignin hydrogenolysis in supercritical ethanol.The most active catalysts are Ru/C and Pt/ZrO2 which provide the high conversion of wood (to 78.0 wt%), significant yield of liquid products (to 50.6 wt%) and low yield of solid rest (to 22.0 wt%) at temperature 250 °C and H2 pressure 9.0 MPa. These catalysts increase the yield of monomeric compounds in liquid products from 10.5 % to 50.4 % on mass of lignin.GC–MS analysis shows that alkyl derivatives of methoxyphenols (mainly propyl syringol and propyl guaiacol) are dominated in liquid products. Solid products of aspen wood catalytic hydrogenolysis contain mainly cellulose (to 82.2 wt%). Therefore, the catalytic hydrogenolysis in supercritical ethanol in the presence of by functional catalysts Ru/C and Pt/ZrO2 allows to fractionate the aspen wood biomass on cellulose and liquid products enriched with propyl syringol and propyl guaiacol.In catalytic hydrogenolysis of ethanol lignin the yield of alkyl derivatives of methoxyphenols is lower compared to wood. This is probably due to the reduced content of reactive β-O-4 bonds in the structure of ethanol lignin compared to native lignin of aspen wood. As follows from the results obtained, native lignin of wood is easier depolymerized to monomeric compounds in the process of catalytic hydrogenolysis than ethanol lignin, isolated from wood.According to GPC data, the catalysts shift to the region of lower molecular mass the molecular mass distribution of liquid products of aspen wood and ethanol lignin hydrogenolysis.

High-quality and phenolic monomer-rich bio-oil production from lignin in supercritical ethanol over synergistic Ru and Mg-Zr-oxide catalysts

The efficient depolymerization of technical lignin to produce high-quality and phenolic monomer-rich bio-oil is challenging owing to the inherent recalcitrant structure of lignin. In addition, the phenolic fragments formed during lignin depolymerization are highly reactive and easily undergo rapid repolymerization to yield undesired heavy oils or char. In the present work, we report a new hybrid catalyst of Ru/C combined with MgO/ZrO2 that is highly effective at depolymerizing lignin to high-quality bio-oil by a cooperative catalysis of Ru-catalyzed reductive depolymerization and MgO/ZrO2-catalyzed stabilization of the reactive phenolic monomers through in-situ capping of the phenol repolymerization initiator, i.e., formaldehyde, by reaction with ethanol. A screening study of various catalyst combinations, including transition metal catalysts such as Pd, Ni, and Ru supported on carbon or Al2O3 as well as basic oxide catalysts such as MgO, MgO/ZrO2, ZrO2, and Mg-Al mixed oxides, revealed that Ru/C–MgO/ZrO2 was the only combination that had a significant positive synergistic catalytic effect on lignin depolymerization, thereby highlighting its unique and exceptional activity. To elucidate the synergistic roles of Ru and MgO/ZrO2 in lignin depolymerization, their individual and integrated catalysis as well as the effect of the Mg/Zr ratio were systematically investigated through a comprehensive analysis of the bio-oil products using several techniques, including 2D heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy (HSQC-NMR). A high bio-oil yield of 76.2 wt% with a low molecular weight of 401 g/mol, large HHV of 34.47 MJ/kg, and high phenolic monomer yield of 31.44 wt% was successfully obtained over the integrated catalyst of Ru/C and MgO/ZrO2 (Mg/Zr = 3) at 350 °C and 30 bar-H2 after 4 h.

Sulfation of ethanol lignin of abies wood by sulfamic acid in N,N-dimethylformamide medium

The sulfation of ethanol lignin of abies wood by sulfamic acid–urea mixture in N,N-dimethylformamide (DMF) medium was studied for the first time. The effect of the duration of lignin sulfation process on the yield and sulfur content in resulted lignin sulfates was studied. It was shown that the reaction of ethanol lignin sulfation begins and ends in a homogeneous medium. At temperature 100 °C, the sulfur content in lignin varies from 5.4 to 6.8% mass, depending on the process time. The introduction of sulfate groups into the lignin structure was confirmed by FTIR and 2D NMR spectroscopy. It was found that both alcohol and phenolic hydroxyl groups of lignin enter the sulfation reaction. The molecular weight distribution of sulfated ethanol lignin was determined by gel permeation chromatography. The optimized method of synthesis allows to obtain sulfated ethanol lignin with low polydispersity (1.31) and narrow molecular weight distribution (3.25–3.75 kDa).

Comprehensive evaluation of hydro-liquefaction characteristics of lignocellulosic subcomponents

This study investigated the hydro-liquefaction behaviors of cellulose, xylan and lignin in ethanol at various temperatures. The interactions between the reaction medium and individual biomass component under different temperatures were evaluated using the Monte Carlo method. The simulation results indicated that the compatibility from cellulose and xylan system was superior to that of lignin with the elevated temperature. The liquefaction characteristics of cellulose and xylan were highly affected by temperature variation due to the existence of active chemical region and functional groups in the structures. In comparison, the reaction behavior of lignin-containing complicated polyaromatic structure was slightly dependent on the elevated temperature. The variation trend of chemical structures from solid residues was highly related to the nature of the raw feedstock. The properties of bio-oil derived from liquefaction of single biomass composition were also associated with the inherent composition of each biomass subcomponent.

Study of the Structure and Properties of Carbon Gels from Abies Lignin and Tannins

Carbon tannin-lignin-formaldehyde (TLF) gels were obtained for the first time by carbonization of organic xerogels synthesized by sol-gel condensation of formaldehyde with polyphenolic substances isolated from abies wood and bark – ethanol lignin and condensed tannins. The effect of the mass ratio of the tannins/lignin (T/L) components in the range 1:0 – 1:2 on the specific surface areas, porous volume, apparent density, and microstructure of carbon tannin-lignin-formaldehyde gels has been studied. It was found that the density of the carbon gels increases from 0.52 to 0.60 g/cm3 with a rises in the T/L ratio from 1:0 to 1:0.2 and 1:0.5 in the initial gel and then decreases to 0.20 and 0.13 g/cm3 with an increase in the lignin content to T/L ratios of 1:1 and 1:2, respectively. The study of the porous structure of carbon gels by the BET method showed that the carbon TLF gel obtained at a T/L ratio 1:2 is characterized by the highest specific surface area (538 m2/g). Using scanning electron microscopy, the structures of TF and TLF carbon gels have been studied. It has been established that the size of globular particles has a decisive influence on the structure of gels. The size of the globule particles increases with increasing of lignin content in the composition of the tannin-lignin-formaldehyde gel that leads to the formation of a less ordered structure of the carbon gel. The porous structure of TLF carbon gels obtained from abies polyphenolic substances can be regulated by varying the ratio of tannins:lignin. The obtained carbon gels can be used as sorbents and catalyst supports

Synthesis and Study of Copper-Containing Polymers Based on Sulfated Ethanol Lignin of Abies Wood

For the first time water soluble copper-containing polymers based on sulfated ethanol lignin of abies wood were obtained by the method of ion exchange. Their composition and structure were studied with the use of elemental and chemical analysis, infrared spectroscopy (IR), atomic absorption, electron paramagnetic resonance (EPR). The absence of nitrogen for copper cations in the resulting polymer indicates the complete substitution of ammonium cations in the ammonium salt of sulfated ethanol lignin. In EPR spectrum of copper-containing sulfated ethanol lignin there is a superposition of two signals. One of them belongs to isolated Cu2+ ions, the other to exchange-bound Cu2+ ions in salt-like compounds. The integral intensity of signal of isolated Cu2+ ions (anisotropic signal) and exchange-bound ions (isotropic signal) depends on the copper content in the polymer

Optimization of the process of abies ethanol lignin sulfation by sulfamic acid–urea mixture in 1,4-dioxane medium

The new process of abies ethanol lignin sulfation by a low-toxic mixture of sulfamic acid and urea in 1,4-dioxane medium was optimized, and the structure of sulfated ethanol lignin was studied. The process of lignin sulfation is described by a first-order equation in the temperature range 70–100 °C. The value of the rate constants is weakly dependent on the ratios of lignin and sulfating complex (sulfamic acid–urea mixture). The activation energy of the sulfation process decreases from 11.5 to 7.5 kJ/mol with an increase in the content of the sulfating complex (SC). The optimal conditions for sulfation of abies ethanol lignin with a high yield of water-soluble sulfated lignin [(100% of mass) with sulfur content of 7.9%] were found: temperature 95–100 °C, L/SC ratio 1:2.3–1:2.9, time 2 h. The composition and structure of water-soluble sulfated ethanol lignin were determined by elemental analysis, FTIR spectroscopy, two-dimensional NMR spectroscopy and gel permeation chromatography. It was shown that only alcoholic OH groups of ethanol lignin react with sulfamic acid. Sulfated ethanol lignin has a higher molecular weight and a lower degree of polydispersity compared to the initial ethanol lignin.

Catalytic Alcoholysis of Lignin with HY and ZSM-5 Zeolite Catalysts

Here, the zeolite catalysts HY and ZSM-5 were used for liquefaction of lignin in supercritical ethanol (Sc-EtOH) to improve the bio-oil yield and control the product distribution. The effects of the reaction temperature (260–380 °C), reaction time (30–120 min), and catalyst content (5.00–15.00 wt %) were investigated. In Sc-EtOH, lignin treated with 10.00 wt % HY catalyst at 360 °C for 60 min resulted in a bio-oil yield of 59.13 wt % and a total hydrocarbon content of 31.26%. Under the same conditions with 10.00 wt % ZSM-5 catalyst, the bio-oil yield was 51.77 wt % and the total hydrocarbon content was 10.34%. This showed that there were large differences in the bio-oil yield and distribution of hydrocarbons (alkanes, olefins, and aromatic hydrocarbons) using the two catalysts. A large amount of alkanes and aromatic hydrocarbons was produced from lignin in the presence of the HY and ZSM-5 zeolite catalysts, respectively. This revealed that the primary reaction over HY was isomerization, whereas that over ...

Structure and properties of organic xerogels derived from tannins and ethanol lignins of the Siberian fir

The organic xerogels, prepared from tannins and ethanol lignins of the fir (Abies sibirica), were synthesized for the first time. The influence of the composition of initial mixture and pH on the characteristics of xerogels obtained by sol-gel condensation of formaldehyde with polyphenols of fir has been studied. The possibility of regulating the density and porosity of gels by varying of the concentration of ethanol lignin in the initial mixture was established. It was found that tannin-lignin-formaldehyde gel with low-density (0.11 g/cm3), and very high porosity (92%) is formed at a mass ratio tannins and lignins equal to 1. According to FTIR data, the process of xerogel formation is carried out by cross-linking due to the formation of carbon-carbon and alkyl ethers bonds. SEM method confirmed the formation of branched macromolecular structure of gels from interconnected spherical particles of different sizes. Thermogravimetric analysis demonstrates greater thermal stability of tannin-formaldehyde gels compared with the tannin-lignin-formaldehyde gels. The increase of lignin concentration in gels more than 50–65% (by the mass) reduced the temperature of their intensive mass loss on 23–63 °С. The obtained organic gels are non-flammable polymers, and they can be used as thermal and fire retardant materials.

Hydrogenation of Abies Wood and Ethanol Lignin by Hydrogen in Supercritical Ethanol in the Presence of Bifunctional Catalyst Pt/ZrO₂

The effect of bifunctional catalyst Pt/ZrO₂ on the yield and composition of products of abies wood and ethanol lignin hydrogenation in supercritical ethanol at temperature of 250 °C was established. In the process of abies wood hydrogenation, the catalyst Pt/ZrO₂ increases the degree of conversion of wood from 52.0 to 65.7 wt.%, the yield of liquid products from 31.0 to 38.1 wt.%,.%, and also increases the content of monomeric compounds in the liquid products. In the presence of catalyst, the cellulose content in the solid product of wood catalytic hydrogenation reaches to 77.1 wt.%, and the content of lignin and hemicelluloses decreases to 21.2 wt.% and 1.7 wt.%, respectively. In the process of ethanol lignin hydrogenation the catalyst Pt/ZrO₂ increases the degree of lignin conversion from 86.0 to 99.4 wt.%, the yield of liquid products from 75.0 to 90.0 wt.%, and also reduces the yield of solid residue from 14.0 to 0.6 wt.% and the yield of gases from 4.7 to 3.3 wt.%. Thus, the polysaccharides of wood biomass complicate the reductive depolymerization of native lignin in comparison with the depolymerization of isolated ethanol lignin. The use of the catalyst Pt/ZrO₂ makes it possible to fractionate the abies wood in supercritical ethanol at 250 °C on solid product with a high content of cellulose, as well as liquid and gaseous products from lignin and hemicelluloses

A Kinetic Study of the Thermal Degradation of Fir and Aspen Ethanol Lignins

Thermogravimetric (TG/DTG) methods have been used to study the thermal destruction of fir and aspen ethanol lignins at different heating rates in an inert (argon) medium. For each of the lignins, the main stages of thermal degradation were found under conditions of programmed heating of samples from 298 to 1173 K at heating rates of 5, 10, and 20 K/min. It was found that with an increase in the heating rate, the ranges of the main degradation of lignins expand. Shifts toward higher temperatures were 13.8 K for fir lignin and 21.1 K for aspen lignin. At the same temperatures, ethanol lignin from aspen showed a greater weight loss than fir lignin. Using the Ozawa–Flynn–Wall, Broido, and Redfern–Coats kinetic models, the results of the thermogravimetric analysis of the studied lignins are analyzed and the values ​​of the activation energy are calculated. The most reliable values of ​​the activation energy were obtained by the Ozawa–Flynn–Wall isoconversion method for the main temperature range of degradation (from ~569 to ~725 K): 113 kJ/mol for fir ethanol lignin and 106 kJ/mol for aspen ethanol lignin.

Formic acid assisted liquefaction of lignin in water and ethanol, investigated for a 0.025 and a 5 L batch reactor: Comparison of yields and compositions of the products

Formic acid assisted conversion of lignin to liquids (LtL-process), where lignin is hydrodeoxygenated in a one-step conversion, produces bio-oils with a molecular weight range of 300–600 Da that comprise a complex mixture of monomeric phenols, e.g., phenol, cresol, guaiacol, catechol, etc., and more hydrogenated products. This paper addresses depolymerisation of lignin at small and large lab scales and includes characterisation of the products. Lignin conversion is performed using a 5 L stirred reactor and a 0.025 L unstirred reactor to evaluate the effect of increased volume and stirring on the oil yield and oil quality. The amount of oil yields is investigated for different types of lignin/lignin-rich residues, reaction temperatures (320–380 °C), reaction times (0.75–3 h) and reaction solvents (aqueous or ethanolic), and have been shown to be highest for the 0.025 L reactor. Furthermore, the relationship between the yields and reaction conditions are systematically explored using principal component analysis (PCA). For the Eucalyptus lignin-rich residue, ethanol tends to give higher oil yields (36–52 wt%) at most of the operating temperatures compared to water as reaction solvent (20–50 wt%). At both reaction scales and both solvent-systems, oil yields tends to decrease at reaction temperatures above 350 °C due to increased char formation. Reaction time does not seem to have any significant effect on oil yield at either scale. More than 40 wt% of the input lignin can be recovered as oil at 320 °C at both scales and solvent systems.

Functionality study of lignin as a tyrosinase inhibitor: Influence of lignin heterogeneity on anti-tyrosinase activity.

Valorization of lignin based on its biological activities is always suffering the restriction from lignin heterogeneity, including wide molecular weight distributions and variable functional group contents. In this work, organosolv ethanol lignin (OEL) from corn stalk was divided into four fractions by multiple organic solvent successive extraction and the anti-tyrosinase activities of four obtained fractions were compared to evaluate the effect of lignin heterogeneity on the anti-tyrosinase activity. The characterization revealed that the successive extraction realized the fractionation of the heterogeneous OEL into four relatively homogeneous parts with gradually increasing molecular weight and decreasing phenolic OH content. The enzymatic inhibition study showed that the four fractions exhibited obviously different anti-tyrosinase activities and the dichloromethane fraction had the highest tyrosinase inhibition rate (75.12%, 0.5 mg/mL), whose value was comparable to the positive control p-hydroxybenzaldehyde. Besides, the relationships between the anti-tyrosinase activity and the lignin properties (purity, molecular weight and phenolic OH) were discussed to elucidate the possible formation mechanism of differences among the four lignin fractions in anti-tyrosinase activity. Consequently, these results suggest that lignin heterogeneity has a significant effect on the tyrosinase inhibition rate, and lignin fractionation is an effective way to screen lignin fractions with high anti-tyrosinase activity.

Characterization and evaluation of antioxidation of lignin from bamboo powder using a formic acid-catalyzed ethanol organosolv process

The antioxidant activity of lignin for producing biochemicals has attracted attention. In this paper, a separation method for lignin is proposed, with high-yield and high-antioxidant activity by using a formic acid-catalyzed subcritical ethanol process. The formic acid-catalyzed ethanol lignin (EOL/FA) and ethanol organosolv lignin (EOL) were first prepared using a high-pressure autoclave at different formic acid dosages. Then, the antioxidant activity and the structural and thermal properties of EOL/FA, EOL, alkali lignin, and sodium lignosulfonate were analyzed using antioxidant analysis, Fourier transform infrared (FTIR) spectroscopy analysis, and thermogravimetric analysis (TGA). The phenolic hydroxyl content of the four lignins was also determined by the Folin–Ciocalteau colorimetric method. Results showed EOL/FA had a higher radical scavenging ability and higher total phenolic hydroxyl content than industrial lignin. It indicated that the formic acid-catalyzed subcritical ethanol process was effective for enhancing the antioxidant activity of lignin.

Relationship of thermal degradation behavior and chemical structure of lignin isolated from palm kernel shell under different process severities

Lignin has been considered to be a potential feedstock to produce phenols chemicals by fast pyrolysis technology because of its aromaticity. In this work, four types of lignin were isolated from palm kernel shell with different severities: milled wood lignin (MWL), alkali lignin (AL), Klason lignin (KL), and organosolv ethanol lignin (OEL). A deep investigation of the relevance of the pyrolysis behaviors and chemical structure was carried out by FTIR, GPC, 2D-HSQC-NMR, TGA-FTIR and Py-GC/MS. AL contained highest content of β-O-4 aryl ether bond (53.9/100 Ar) and highest value of S/G ratio (1.68). MWL showed the widest temperature range (126–536 °C) of thermal degradation because of its inhomogeneous distribution of molecular weight. Highest content of oxygen-containing non-condensable gas components (H2O, CO2, CO) was observed in AL. The dominant organic components from lignin pyrolysis were S-type phenols, G-type phenols, P-type phenols, and C-type phenols. G-type (9.74–26.01%) was the dominant phenols products in AL, while P-type (44.23–56.01%) for KL, P-type (29.38–56.07%) for OEL, and G-type (9.08–25.81%) and P-type (22.60–29.04%) in MWL. Higher pyrolysis temperature promoted the formation of aromatics. As the conversion rate increased from 0.1 to 0.8, the activation energy estimated from DAEM model of four types of lignin, all gradually increased.

Study of the Thermochemical Properties of Ethanol Lignins from Abies and Aspen Wood

Study of the Thermochemical Properties of Ethanol Lignins from Abies and Aspen Wood

Catalytic in Situ Hydrogenolysis of Lignin in Supercritical Ethanol: Effect of Phenol, Catalysts, and Reaction Temperature

This study aimed to explore the in situ hydrogenolysis of alkali lignin into bio-oil over three kinds of heterogeneous catalysts with varied catalytic properties (Ru/C, Ni/ZSM-5, and CuNiAl hydrotalcite-based catalyst) in supercritical ethanol. Phenol was first introduced to the in situ hydrogenolysis system to form a complex solvent to improve the lignin depolymerization over heterogeneous catalysts. The promotion effect of phenol was obviously observed during the hydrogenolysis process, leading to improved bio-oil yield and decreased solid residue yield, due to the unique dissolution and diffusion properties of phenol-containing solvent. The synergistic effects of basic sites and complex solvents were observed; thus, herein, the effect of catalysts, reaction temperature, and time on the hydrogenolysis, repolymerization, and coking on catalysts was investigated in detail, considering the molecular weight, elemental composition, and higher heating value (HHV) of bio-oil. The highest bio-oil yield was up t...