Liquefaction Of Lignin Research Articles

Degradation of lignin in ionic liquid with HCl as catalyst

Lignocellulosic materials consist of 10−30% lignin by weight and 40% by energy (Perlack et al., 2005). As the highest energy component of plant biomass, lignin is composed of phenol units. Eco‐friendly degradation of lignin in ILs provides an important way to utilize it efficiently. In this study, 1‐methyl‐3‐benzylimidazolium chloride (BnMIMCl) and 1‐methyl‐3‐benzylimidazolium trichloroacetate (BnMIMTFA) were applied for degradation liquefaction of lignin. The highest liquefaction efficiency of 75.45% was obtained under the optimized condition. This attributed to the good dissolving capability and assistance of ILs to lignin during the degradation. GC‐MS analysis showed that 60% of low molecular products were phenols. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 809–814, 2016

Preparation and Characterization of Lignin Polyols from the Residues of Oil Palm Empty Fruit Bunch

In this work, lignin polyols were prepared from the liquefaction of kraft lignin and from the direct liquefaction of Elaeis guineensis lignocellulosic waste. The liquefaction reaction was performed with polyhydric alcohols using sulfuric acid as catalyst at 160 °C. The physical and chemical characterizations of lignin and lignin polyols were conducted by elemental analysis, Fourier transform-infrared spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, molecular weight distribution, and thermogravimetric analysis (TGA). Quantitative 13C NMR showed that all aliphatic hydroxyl group values of polyols noticeably increased with the use of the two methods compared to kraft lignin. The average molecular weight analysis of the liquefied product showed that it exhibited high molecular weight compared to kraft lignin. Both structural and thermal characteristics suggest that lignin polyols would be a good substitute for kraft lignin in the synthesis of polymeric compounds such as environmentally friendly resins or wood adhesives, as it presents higher amounts of activated free ring positions, higher molecular weight, and high thermal stability.

Ethanol-Enhanced Liquefaction of Lignin with Formic Acid as an in Situ Hydrogen Donor

The conversion of biomass into biofuel using solvents that come from biomass itself is being more and more important for the concern of renewable development and CO2 netural. Formic acid was used as an in situ hydrogen donor for the liquefaction of wheat straw alkali lignin. It was found that the addition of ethanol improved the yield of monophenols remarkably. Although ethanol exhibited a poor effect in the liquefaction of lignin, it was found to be a good assistant solvent for improving the monophenol yield of the formic acid system significantly.

Effect of Catalyst Properties on Hydrocracking of Pyrolytic Lignin to Liquid Fuel in Supercritical Ethanol

The metal-acid bifunctional catalysts have been used for bio-oil upgrading and pyrolytic lignin hydrocracking. In this work, the effects of the metal-acid bifunctional catalyst properties, including acidity, pore size and supported metal on hydrocracking of pyrolytic lignin in supercritical ethanol and hydrogen were investigated at 260 °C. A series of catalysts were prepared and characterized by BET, XRD, and NH3-TPD techniques. The results showed that enhancing the acidity of the catalyst without metal can promote pyrolytic lignin polymerization to form more solid and condensation to produce more water. The pore size of microporous catalyst was smaller than mesoporous catalyst. Together with strong acidity, it caused pyrolytic lignin further hydrocrack to numerous gas. Introducing Ru into acidic catalysts promoted pyrolytic lignin hydrocracking and inhibited the polymerization and condensation, which caused the yield of pyrolytic lignin liquefaction product to increase significantly. Therefore, bifunctional catalyst with high hydrocracking activity metal Ru supported on materials with acidic sites and mesopores was imperative to get satisfactory results for the conversion of pyrolytic lignin to liquid products under supercritical conditions and hydrogen atmosphere.

Optimizing the lignin based synthesis of flexible polyurethane foams employing reactive liquefying agents

The present work is focused on the optimization of a green process based on the employment of by-products obtained from wood treatments as raw materials for producing flexible polyurethane foams. More specifically, lignin was employed in flexible polyurethane foams in order to partially replace the usual fossil polyols; therefore glycerol (GLY) and glycerin polyglycidyl ether (EJ 300) were used as the polyol fraction for lignin liquefaction. Polypropylene glycol triol was used as a chain extender in different ratios with liquefaction solvents, and polymeric diphenylmethane diisocyanate as an isocyanate fraction. Liquefaction of lignin was performed by microwave irradiation, thus reducing the processing time and energy required compared to present industrial production processes. All the foams were produced in controlled expansion through the adoption of a ‘one-shot’ approach, using water as a blowing agent and with an isocyanate index (NCO/OH) of less than 100 to improve the flexibility of the foam. This approach allowed for the substitution of up to 12% of common petro derived polyol with commercial soda lignin. Finally, the foams were characterized, presenting properties that could be modulated as a function of lignin content, GLY/EJ 300 ratio and isocyanate index. The qualities of the foams were compatible with existing materials used for furniture and for the interiors of car seats and couches. © 2015 Society of Chemical Industry

FTIR as a simple tool to quantify unconverted lignin from chars in biomass liquefaction process: Application to SC ethanol liquefaction of pine wood

Lignin in solid residues produced from wood liquefaction can be quantified by FTIR analysis. This is applied to investigate pine wood liquefaction in supercritical ethanol in comparison with model lignin and cellulose in order to achieve a thorough description of wood liquefaction in SC ethanol. The proportions of lignin, hemicelluloses, cellulose and chars in the solid residue were quantified by compositional analysis based on acid hydrolysis combined to the quantitative FTIR analysis of the νCC vibration of lignin at 1514cm−1. It was shown that SC ethanol is an efficient medium for an easy liquefaction of lignin and hemicellulose from pine wood. Native cellulose in pine wood was only slightly attacked by contrast to microcrystalline cellulose. From pine wood, gas production is limited to 3wt.% and total yields in liquid products achieved 45wt.% but only one fourth of liquid products were eluted by GC–MS.

Microwave assisted liquefaction of wheat straw alkali lignin for the production of monophenolic compounds

The microwave assisted liquefaction process of wheat straw alkali lignin was investigated to obtain monophenolic compounds as the precursor of bio-fuel. It is found that the total yield of monophenolic compounds is significantly improved under microwave irradiation, reaching 15.77% under a relatively mild liquefaction condition of 10 wt% H2SO4 as the catalyst, 10 wt% phenol as the hydrogen-donor reagent at 120 °C for 40 min. Compared with conventional thermal liquefaction process, microwave irradiation promotes the cleavage of C–C bonds, which gives an extra 29% of Caryl–Cα bond cleavage, and increases the yield of monophenolic compounds from 0.92% to 13.61% under the same conditions. The excessive temperature and prolonged time under microwave irradiation will promote the recondensation of degraded lignin fragments, so the key to obtain high yield of monophenolic compounds is to avoid the recondensation reaction. The selected solid catalyst promotes the dissociation of methoxy groups, and the addition of phenol into liquefaction can only slightly improve the yield of monophencolic compounds.

Flexible polyurethane foams green production employing lignin or oxypropylated lignin

An innovative and green chemistry synthetic approach was developed in order to employ lignin for the production of flexible polyurethane foams. Soda lignin and oxypropylated soda lignin were tested and compared. Glycerol and PEG 400 were used as polyol fractions for lignin liquefaction by microwave irradiation, which represents a novel green processing technique. The samples were produced with the “one-shot” technique, using two types of chain extenders in combination with liquefied lignin: castor oil and polypropylene glycol triol. Water was used as a single natural blowing agent, and polymeric diphenylmethane diisocyanate (PMDI) was employed as the isocyanate fraction. The work was carried out keeping the NCO/OH less than one hundred, thus enhancing the flexibility due to a lower crosslinking degree; all the foams were produced in free and controlled expansion. Two of the most efficient chain extenders were individuated thus introducing flexible chains into the macromolecular structure that can reduce the glass transition temperature of the materials and therefore generate foams with higher flexibility. The properties of the produced foams were compatible with the technical requirements for applications in packaging and for the production of the interior part of car seats.

C4H8SO3Hmim]HSO4 as an efficient catalyst for direct liquefaction of bagasse lignin: Decomposition properties of the inner structural units

Catalytic valorization of renewable aromatic lignin is attracting increasing attention. In this study, an efficient method for direct liquefaction of sugarcane bagasse lignin using acidic ionic liquid (IL) 1-(4-sulfobutyl)-3-methyl imidazolium hydrosulfate ([C4H8SO3Hmim]HSO4) is presented. The relationships between catalyst dosage, reaction condition parameters and degree of liquefaction, and the structure and elemental composition of liquefaction residue were investigated. The transformation performances of three molecular structural units (guaiacyl, syringyl, and hydroxyphenyl units) of bagasse lignin were also intensively examined using gas chromatography-mass spectrometry, elemental analysis, Fourier transform infrared spectrometry, and proton nuclear magnetic resonance characterization. The results demonstrated that the dual-functionalized acidic IL exhibited excellent catalytic performance in the direct liquefaction process. More than 65% degree of liquefaction was achieved under optimized conditions, yielding 13.5% of useful aromatic fine chemicals such as phenol, 4-ethylphenol, and guaiacol. The p-hydroxyphenyl unit of lignin was the most flexible, followed by the guaiacyl unit, whereas the syringyl group was the most refractory. Furthermore, the catalytic mechanism was proposed.

Hydrotreating of wheat straw in toluene and ethanol.

In the present work, wheat straw was hydroliquefied at a temperature of 300°C for 4h in ethanol or toluene in order to obtain bio-components which are useful for fuel purposes. The experiments were performed in a 100mL batch reactor under hydrogen pressure of 70 bar. Typically, 2g of straw and 0.1g of catalyst (66%Ni/SiO2-Al2O3) were dispersed in 15 g of solvent. The main compounds of the oil produced during the liquefaction of hemicellulose, cellulose and lignin of wheat straw in both solvents are: tetrahydrofuran-2-methanol, 1,2-butanediol and butyrolactone. Besides the mentioned compounds, ethanol favoured the decomposition of bigger molecules to short-chain alcohols such as 1-butanol, 1,2-propanediol and 1,2-ethanediol. Toluene contributes to the production of furans and other cyclic compounds. The light fractions distilled together with the solvent also contain the following: 1-propanol, 2-methyl-cyclopentanone, acetic acid and ethyl acetate.

Fingerprinting Bio-Oils from Lignocellulose and Comparison with Fossil Fuels

Positive and negative electrospray ionization–mass spectrometry, gas chromatography–mass spectrometry and Fourier transform infrared spectroscopy were used as complementary “fingerprinting” techniques for an initial evaluation of bio-oils from lignocellulose with different origins and degrees of upgrading and also for a comparison with petroleum based fuels. The tabulated spectra and chromatograms were interpreted using principal component analysis (PCA). The samples were crude fast pyrolysis oils from different wood feedstock, bio-oils made by liquefaction of lignin (lignin-to-liquid, LtL), hydrodeoxygenated (HDO) and more extensively hydrotreated (HT) fast pyrolysis oils and some petroleum based fuels. The major trend is that the crude pyrolysis oils from different laboratories and feedstock are relatively similar in composition, and different from the LtL, HDO and HT oils and the petroleum based fuels. However, pyrolysis oils made of mixtures of spruce, bark and needles are particularly influenced by t...

Hydrothermal conversion of lignin to substituted phenols and aromatic ethers

Hydrothermal liquefaction of lignin was performed using methanol and ethanol at various temperatures (200, 250 and 280°C) and residence times of 15, 30 and 45min. Maximum liquid product yield (85%) was observed at 200°C and 15min residence time using methanol. Increase in temperature was seen to decrease the liquid products yield. With increase in residence time, liquid yields first increased and then decreased. FTIR and 1H NMR showed the presence of substituted phenols and aromatic ethers in liquid products and breakage of β-O-4 or/and α-O-4 ether bonds present in lignin during hydrothermal liquefaction was confirmed through FTIR of bio-residue. In comparison to the existing literature information, higher lignin conversion to liquid products and maximum carbon conversion (72%) was achieved in this study.

Selective Liquefaction of Lignin from Bio-ethanol Production Residue Using Furfuryl Alcohol

In order to obtain “clean” liquefied lignin, selective liquefaction of lignin from bio-ethanol production residue (BEPR) was conducted using an aromatic solvent, furfuryl alcohol. The effects of liquefaction time, temperature, and liquid ratio on the liquefaction yield were investigated. The results indicated that with the increasing of liquefaction temperature (120 to 170 °C) or liquid ratio (3 to 5:1), the liquefaction yield of lignin (LYL) increased, respectively. Liquefaction times of 15 to 120 min had no significant effect on the liquefaction yield. When liquefaction was conducted at 170 °C for 15 min with a ratio of 5/1 liquefying solvent to raw material, the LYL reached its highest level of 80.23%. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Gel permeation chromatography (GPC) analyses confirmed that the liquefaction process had great selectivity for lignin. Ash and carbohydrates in the raw material could be removed as liquefied residue.

Lignin liquefaction under microwave heating

ABSTRACTOrganosolv lignin from olive tree pruning was subjected to liquefaction under microwave heating and modifying the experimental conditions (time, temperature, and concentration of catalyst) according to an experimental design. The organosolv lignin and obtained polyols were characterized using attenuated‐total reflection infrared spectroscopy (ATR‐IR), thermogravimetric analysis (TGA), gel permeation chromatography, and another parameter such as the hydroxyl number (IOH). The ATR‐IR and the TGA results showed that the solvents (polyethylene glycol #400 and glycerol) reacted with the lignin being present in the final product. The optimal polyol showed a liquefaction yield of 99.07% that was obtained in 5 min of reaction at 155°C with 1% of sulphuric acid. The liquefaction product showed a hydroxyl number of 811.8 mg KOH/g, suitable to be used as a precursor in polyurethane foam synthesis. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3292–3298, 2013

Influence of RANEY Nickel on the Formation of Intermediates in the Degradation of Lignin

Lignin forms an important part of lignocellulosic biomass and is an abundantly available residue. It is a potential renewable source of phenol. Liquefaction of enzymatic hydrolysis lignin as well as catalytical hydrodeoxygenation of the main intermediates in the degradation of lignin, that is, catechol and guaiacol, was studied. The cleavage of the ether bonds, which are abundant in the molecular structure of lignin, can be realised in near-critical water (573 to 673 K, 20 to 30 MPa). Hydrothermal treatment in this context provides high selectivity in respect to hydroxybenzenes, especially catechol. RANEY Nickel was found to be an adequate catalyst for hydrodeoxygenation. Although it does not influence the cleavage of ether bonds, RANEY Nickel favours the production of phenol from both lignin and catechol. The main product from hydrodeoxygenation of guaiacol with RANEY Nickel was cyclohexanol. Reaction mechanism and kinetics of the degradation of guaiacol were explored.

Observation by light microscope of sugi (Cryptomeria japonica) treated with the ionic liquid 1-ethyl-3-methylimidazolium chloride

To establish an effi cient method for effective utilization of lignocelluloses, many studies on lignocellulose conversion technology have been carried out. A promising novel method is treatment with ionic liquids, which are organic salts with melting points in the vicinity of ambient temperature. Ionic liquids have many notable characteristics such as negligible vapor pressure, thermal stability, recyclability, and nonfl ammability. It has been found that some ionic liquids are able to dissolve cellulose, and there have been several reports on applications of ionic liquids to cellulose. Previous work has shown that wood components are decrystallized and depolymerized as they are liquefi ed by treatment with ionic liquids. The differences in the reaction behavior of two different wood species with ionic liquid have been studied. Signifi cant differences in lignin liquefaction behavior were explained by differences in the chemical structure of the lignin in the two wood species. The reaction atmosphere was also found to infl uence the liquefaction of wood. Although many studies on ionic liquid treatment of wood have already been reported, the resulting morphological changes of wood have not been elucidated. For that reason, in the present study, the morphological changes in wood after treatment with the ionic liquid 1-ethyl-3-methylimidazolium chloride were studied by light microscopy.

Classified Separation of Lignin Hydrothermal Liquefied Products

Alkaline lignin was liquefied under hydrothermal conditions, and the liquefied products were effectively separated into four main types of substances: benzenediols, monophenolic hydroxyl products, weak-polar products, and water-soluble products (low-molecular-weight organic acids, alcohols, etc.). The production process and yield of each classified products are discussed. More than half of the yields of the oil products consisted of phenolics. A mechanism for phenolic production from lignin liquefaction is proposed. It suggests that the decomposition of lignin under hydrothermal conditions occurs mainly by three steps: hydrolysis and cleavage of the ether bond and the C–C bond, demethoxylation, and alkylation.

Polycondensation reaction and its mechanism during lignocellulosic liquefaction by an acid catalyst: a review

The increase in the residue content resulting from polycondensation would be adverse to the utilization of lignocellulose and to the quality of products obtained from liquefied lignocellulosic material. The yield of the residue formed from liquefaction and the mechanism of polycondensation were reported mainly by Lin, Yamada and Kobayashi. The major products of cellulosic liquefaction are levulinic acid and hydroxymethylfurfural (HMF) derivatives under polyhydric alcohols and phenolated compounds under phenols. The cleavage of the β-O-4 bonds is the major reaction pathway of lignin liquefaction under various liquefying reagents regardless of whether they contain acid catalysts or not. The break up compounds by decomposition are polymerized to substances with high molecular weight by polycondensation in lignocellulosic liquefaction. The molecular weight of condensed residues increases almost linearly as a function of liquefaction time at the later stage of lignocellulosic liquefaction. The longer the time required, the greater the content of new residue generated by polycondensation during the entire process of liquefaction. We conclude that the condensed residues may stem from the interaction of degraded lignin and cellulose components in wood or from the products of two major components reacting with liquefying reagents.

Antioxidant abilities comparison of lignins with their hydrothermal liquefaction products

Black liquor alkaline lignin and magnesium lignosulfonate were liquefied at 320 oC. The antioxidant abilities of the liquefaction products were compared with the raw materials. Results showed that the total phenol content and unit antioxidant power of both alkaline lignin liquefaction products (ALLP) and magnesium lignosulfonate liquefaction products (MLLP) were improved, and ALLP had a larger increase than MLLP. The influence of reaction time and temperature on oil yield, total phenol content, and antioxidant power of ALLP was evaluated. The total phenol content was found to have certain relationships with the antioxidant abilities. These results explore a new approach for further studies and applications of liquid antioxidant from lignins.

Liquefaction of lignin by polyethyleneglycol and glycerol

Enzymatic hydrolysis lignin (EHL), isolated from the enzymatic hydrolysis residues of the biomass, was liquefied using the mixed solvents of polyethyleneglycol (PEG) and glycerol at the temperature of 130-170°C with sulfuric acid as a catalyst. The influences of liquefaction parameters, such as the molecular weight of PEG, mass ratio of sulfuric acid to EHL, liquefaction temperature and time, and mass ratio of liquid (liquefying cosolvent) to solid (EHL) on the residue content and hydroxyl number were discussed. The FT-IR spectrum result showed that the liquefaction product of EHL was polyether polyol. The hydroxyl number of the liquefaction product was 80-120 mgKOH/g higher than that of PEG.