Direct liquefaction of different lignocellulosics and their constituents: 2. Molecular weight determination,gas chromatography,i.r. spectroscopy

Oils derived by thermochemical conversion of different lignocellulosic feedstocks have been comparatively characterized. The average molecular weights (MW) were determined of oils and their SESC-fractions by use of high performance gel permeation chromatography. The MW of the oils varied between 230 (spruce holocellulose) and 540 Dalton (spruce organosolv lignin), while those of the SESC fractions increased with increasing polarity. Capillary g.c. was used to quantify monomeric phenols. No aromatic compounds could be detected in the oil from pure cellulose. I.r. spectra of the oils were evaluated quantitatively; multiple linear regression analysis revealed that the amounts of different types of phenols and the oxygen content can be calculated approximately from the i.r. data.     

Water vapor sorption and diffusivity in bark

Physical properties of importance in drying processes have been compiled for bark, including spruce, pine, and birch in Sweden. Water vapor sorption isotherms were determined for the bark of these trees. At 95% relative humidity and 25°C, outer birch bark reached a moisture ratio (kg water/kg dry mass) of 5%, whereas inner birch bark, spruce bark, and pine bark reached moisture ratios of 21, 28, and 25%, respectively. The transverse water vapor diffusivity in samples of spruce bark, pine bark, inner birch bark, and outer birch bark were determined to be 1.1–1.7 · 10^?6, 2.2–9.2 · 10^?7, 1.5–2.6 · 10^?6, and 4.3–13 · 10^?8 m²/s, respectively. The in-plane diffusivity was of the same magnitude as the transverse diffusivity in inner birch bark, whereas in outer birch bark the in-plane diffusivity was several times higher than the transverse diffusivity. These data can be used to model the drying behavior and can thus aid in the design of efficient bark drying processes.     

Antioxidant activity of pine bark procyanidins in bulk corn oil and corn oil‐in‐water emulsions

In this work, the ability of pine bark procyanidins to hinder oxidation in bulk corn oil and corn oil‐in‐water‐emulsion has been investigated. A preliminary characterisation of the obtained aqueous (AF) and organic (OW) fractions and subfractions suggested a very polar character and showed that both fractions possess remarkable antioxidant activity when minimum concentrations of 2 mg/mL are used. OW fractions and subfractions derived from both pine varieties were able to inhibit oxidation in oils. More specifically, two organic subfractions were the most efficient for retarding the degradation process, with levels of 62% and 50% after 8 days of treatment, respectively. Organic subfractions obtained from both varieties of pine also rendered possible inhibition levels in oil‐in‐water‐emulsions up to 80% after 4 days of oxidation, more than 3 times higher than the levels provided by tocopherol, a well‐known model commercial antioxidant, which confirms the excellent antioxidant potential of procyanidins from pine bark. Practical application: Lipid deterioration leads to losses in quality and nutritional value and to the development of off‐flavours in many foodstuffs. One way to overcome this drawback is by using antioxidants of natural origin, which is a subject of a great scientific and industrial interest, reflected by the growing number of papers and patents published during the last years. Since aqueous and organic fractions obtained from Pinus pinaster and Pinus radiata bark turned out to be an adequate source of procyanidins in previous investigations of our group, their possible antioxidant role in model lipid systems was investigated. This approach entails also another benefit in terms of waste valorisation, since pine bark is a typical residue of agroforestal industries.     

Analysis of sterol fractions from twenty vegetable oils

The unsaponifiables separated from 20 vegetable oils were divided into sterol and three other (less polar compound, triterpene alcohol, and 4-methylsterol) fractions by preparative thin layer chromatography. The amounts of the sterol fractions were more than ca. 30% in the unsaponifiables from all of the oils, except tohaku, pumpkin seed, and fagara seed oils. Composition of the sterol fractions were determined by gas liquid chromatography. Individual components of the sterol fractions were identified by gas liquid chromatography and combined gas liquid chromatography-mass spectrometry. β-Sitosterol was found as the most predominant component in the sterol fractions from all oils, except two, i.e. the sterol fraction from pumpkin seed oil contained no detectable amount of β-sitosterol and the sterol fraction from akamegashiwa oil contained Δ⁵-avenasterol as the most abundant component. Campesterol, stigmasterol, Δ⁵-avenasterol, Δ⁷-stigmastenol, and Δ⁷-avenasterol and also trace amounts (at the very least) of cholesterol and brassicasterol were found in most of the oils analyzed. It may be noted that a large amount (ca. 9%) of cholesterol was detected in the sterol fraction from capsicum seed oil. The presence of 24-methylenecholesterol and Δ⁵-avenasterol in the sterol fraction of akamegashiwa oil was demonstrated by isolation of these sterols.     

Miscanthus sinensis fractionation by different reagents

Miscanthus sinensis L. was fractionated by different reagents (ethanol, soda and soda–ethanol) in order to obtain cellulose, hemicelluloses and lignin. Characterization of original M. sinensis fibres (66.6% holocellulose, 36.1% α-cellulose, and 15.5% lignin) was done and compared with other biomass species chemical composition (alternative raw materials, agriculture residues, coniferous and leafy plants). Obtained solid fractions were chemically characterized and compared with solid fractions from other biomass products (palm oil empty fruit bunches (EFB) and rice straw) generated by similar fractionation processes (soda and organosolv). Soda process produced the solid fraction with the highest content in α-cellulose and lowest content in lignin revealing a strong fractionation effect. On the contrary, soda–ethanol process was found to present low fractionation capability. Obtained cellulose samples were characterized by FTIR to complete the chemical structure analysis. Lignin samples isolated from the liquid fractions were submitted to FTIR, ¹H NMR, GPC, DSC and TGA in order to suggest suitable applications for the products based on their properties.     

Graft copolymers of lignin with electron poor alkenes

The synthesis of copolymers between lignin and electron poor alkenes is described. Lignin from steam‐exploded pine, from steam‐exploded straw, and organosolv were used as starting materials. Beforehand, lignins were fully characterized by using elemental analysis, ultraviolet spectroscopy, gel permeation chromatography (GPC), Fourier transform infrared (FTIR), and both¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy. The synthesis of copolymers was performed using a previously described procedure utilizing calcium chloride and hydrogen peroxide as reagents. FTIR of copolymers showed absorptions due to the presence of both lignin and the electron withdrawing group on the alkene. GPC analysis showed the presence of fractions with high molecular weights: the M_z of lignin from pine was 3729 while the copolymer with methyl acrylate showed M_z = 383790. Differential calorimetry showed the presence of glass transitions in the range of ?9 to 4.5°C due to the presence of grafted polyalkene chains. When acrylonitrile was used as starting material DSC analysis of the product showed a glass transition at 119°C, which can be attributed to grafted polyacrylonitrile chain. Lignin from steam explosion could be a good raw material in the preparation of graft copolymers. Furthermore, lignin from pine gave better results than that from straw. Finally, lignin from steam explosion gave better results than organosolv lignin. These results can be explained on the basis of the structural properties of used lignins. Both UV and ¹³C NMR spectra showed that lignin from pine contained a consistent amount of double bonds. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1163–1171, 2003     

Purification of Biorefinery Lignin with Alcohols

After hydrothermal pretreatment and enzymatic hydrolysis of wheat straw, a slurry rich in lignin but with a high content of inorganic substances, especially silica, and residual carbohydrates is produced. This slurry was used to develop an ethanol organosolv separation method to produce silica-free lignin fractions. The addition of para toluene sulphonic acid (PTSA) and the use of two alternative long-chain alcohols, oleyl alcohol or nonylphenol, were tested. In every reaction, two lignin fractions were produced and their molecular size and elemental composition were characterized. The yield of each fraction and the change in MWD were studied as a function of temperature and solid to liquid ratio. At 100, 150, and 200°C and with the use of PTSA, high-purity lignin fractions were obtained. After lignin fractionation with nonylphenol, a liquid silica-free product with high lignin content was obtained in yields between 17 and 72%.     

Lignin and Other Aromatic Substances Released from Spruce Wood During Pressurized Hot-Water Extraction,Part 1: Extraction,Fractionation and Physico-Chemical Characterization

Ground spruce wood was extracted with pressurized hot water in an accelerated solvent extractor (ASE) at 170°C during 20, 60, and 100 min. Released aromatic substances (from 2.2 to 2.5% on wood basis) were isolated on XAD-7 resin and fractionated into lignin, oligomeric aromatic substances (OAS), and compounds insoluble in methanol (IMC). The separated aromatic fractions, and the ground wood before and after extraction, were characterized by physico-chemical methods (GC, GC-MS, HPLC-SEC, TG, DSC). The major part of the aromatic substances was oligomeric aromatic substances (OAS). This fraction increased significantly with the extraction time, while the yield of dissolved lignin increased only slightly with extraction time. Isolated lignins had a lower molar mass and differed considerably from spruce milled wood lignin (MWL). The isolated lignins were more stable against oxidative thermodegradation than spruce MWL. The UV-extinction coefficients at 280 nm were lower for the isolated lignins than for MWL.     

Structural Variation of Bamboo Lignin before and after Ethanol Organosolv Pretreatment

In order to make better use of lignocellulosic biomass for the production of renewable fuels and chemicals, it is necessary to disrupt its recalcitrant structure through pretreatment. Specifically, organosolv pretreatment is a feasible method. The main advantage of this method compared to other lignocellulosic pretreatment technologies is the extraction of high-quality lignin for the production of value-added products. In this study, bamboo was treated in a batch reactor with 70% ethanol at 180 °C for 2 h. Lignin fractions were isolated from the hydrolysate by centrifugation and then precipitated as ethanol organosolv lignin. Two types of milled wood lignins (MWLs) were isolated from the raw bamboo and the organosolv pretreated residue separately. After the pretreatment, a decrease of lignin (preferentially guaiacyl unit), hemicelluloses and less ordered cellulose was detected in the bamboo material. It was confirmed that the bamboo MWL is of HGS type (p-hydroxyphenyl (H), vanillin (G), syringaldehyde (S)) associated with a considerable amount of p-coumarate and ferulic esters of lignin. The ethanol organosolv treatment was shown to remove significant amounts of lignin and hemicelluloses without strongly affecting lignin primary structure and its lignin functional groups.     

Residual Sugars in Klason Lignin

The Klason method–dissolution of carbohydrates in sulfuric acid–has been widely used for the determination of lignin content in woody materials. It was an unsolved problem, however, whether Klason lignin still contains carbohydrates. We observed previously that Klason lignin becomes almost completely soluble in water after ozone treatment. In this work, the residual sugar content of Klason lignin was determined on the basis of the above observation.

Water-soluble lignin was prepared by ozone treatment (25 and 45 min) of finely-crushed Klason lignin obtained from spruce and birch wood meals. After hydrolysis with 2N-trifluoroacetic acid followed by sodium borohydride reduction, residual sugars were determined by GLC as their alditol acetates.

Klason lignin ozonated for 25 min contained 0.75% and 0.95% neutral sugars for spruce and birch, respectively. Most of the residual sugars were derived from hemicelluloses. Because ozone degrades carbohydrates, the prolonged ozonation was found to decrease the content of residual sugars. Therefore, the values obtained here are the minimum ones for the residual sugar content in Klason lignin.     

Sulfur-free lignins as composites of polypropylene films

To elucidate the effect of lignin addition, polypropylene films containing 2–10 wt % of spruce organosolv lignin and/or beech wood prehydrolysis lignin were compared with lignin-free polymers with respect to tensile strength and elongation before and after aging. The physicochemical properties of the lignin-containing films were investigated by conductivity measurements, surface behavior, and UV and IR spectroscopy. © 1993 John Wiley & Sons, Inc.     

新型橡胶助剂——高沸醇木质素的研制

采用1,4 丁二醇水溶液为溶剂的高沸醇溶剂法,从松木、稻草等原料制备纤维素与高沸醇木质素。使用上述原料,在190～220℃的1,4 丁二醇水溶液中蒸煮1～3h后,分离反应产物,得到固体纤维素与高沸醇木质素-丁二醇溶液。不溶于水的高沸醇木质素通过加水沉淀的方法,从反应后的液体混合物中分离。从松木和稻草制备沸醇木质素的得率分别大于25%和11%。从松木中提取的沸醇木质素的w(灰分)=0 6%,而传统造纸黑液制得木质素磺酸钙的w(灰分)=21 4%。沸醇溶剂法是一种节能、无污染的制备纤维素与木质素的好方法。高沸醇木质素具有较高的反应活性,可以与甲醛反应,形成木质素改性树脂。添加高沸醇木质素改性树脂可以改善NBR橡胶的性能,尤其是扯断伸长率从270%提高到540%,其改性效果优于木质素磺酸盐改性树脂(扯断伸长率330%)。沸醇木质素是一种新型的橡胶添加剂,有良好的应用前景。     

Thermal decomposition and combustion of coals,fuel wood,and hydrolytic lignin,as studied by thermal analysis

Different biofuel woods (spruce, pine, and spruce and pine bark), hydrolytic lignin, and coals from different deposits [D coal from Inta, Zh coal from Vorkuta, and D coal from Khakassia] were studied on a synchronous thermal analyzer at heating rates of 5, 10, and 20 K/min in inert and air atmospheres. Classical thermogravimetric and differential thermogravimetric curves were obtained to describe the thermal decomposition of hemicellulose, cellulose, and lignin and the combustion of a carbon residue as the main components of the biofuel woods. The decomposition of the coal fuels from different deposits was studied, and the temperature ranges of drying, the release of volatile substances, and the combustion of carbon residues were obtained. The results of thermal analyses were processed with the use of an isoconversional method based on the Friedman and Ozawa–Flynn–Wall models and with the aid of an extended independent parallel reaction (EIPR) model. A satisfactory repeatability of the results was obtained to indicate the applicability of both of these methods. The subsequent study of wood, hydrolytic lignin and, coals from different deposits was carried out with the aid of the EIPR model. The activation energies of biofuel woods varied in a range from 62 to 93 kJ/mol, which are much lower than those of coals (104–116 kJ/mol).     

Degradation of lignin with monomethylamine

Wood chips were treated with gaseous mixtures of monomethylamine and water vapour at temperatures between 160 and 120°C and pressurs ranging between 1.5 and 7.0 MPa. The degradation products were subsequently extracted with different solvents at ambient pressure. First, The degradation products of lignin were extracted with highly selective organic solvents such as diethyl ether or 2-butanone. Then, the remaining decomposition products were extracted with water or an aqueous solution of monomethylamine. The latter extract contains the degradation products of the hemicelluloses in a relatively high concentration. After a three hour digestion, the residue obtained from spruce had a lignin content of 3.1 wt-% (pine: 3.7 wt-%; birch 0.3 wt-%). The total yield of unbleached cellulose was approximately 60 wt-%.     

The Effect of Lignin and Bark Wounding on Susceptibility of Spruce Trees to Dendroctonus micans

The effect of lignified stone cell masses (lignin) and mechanical wounding of bark on gallery formation and oviposition by the spruce bark beetle, Dendroctonus micans, was determined in plantations of Norway and Sitka spruce. When beetles were implanted onto trees that varied in bark lignin concentration, there was a significant negative relationship between lignin and adult gallery size. Only a few larval galleries were established, all of them on trees with a low lignin concentration. Results confirm the importance of lignin as a preformed defence in living trees. Adults excavated significantly larger galleries in wounded than unwounded bark. Most larval galleries were also established in wounded bark. The concentrations of nitrogen, carbohydrate, and resin and the moisture content of wounded and unwounded bark were measured at the beginning of the experiment. A number of significant changes were induced by wounding, including an increase in the concentration of nitrogen and starch, and decreases in the moisture content and the concentration of free sugars. There was no overall effect of wounding on resin content of bark, although concentrations were significantly lower in new than old wounds. An increase in the nutritional quality of bark following wounding appears to be the main factor influencing attacks on wounded trees by D. micans.     

Analysis of methylsterol fractions from twenty vegetable oils

The 4-monomethylsterol and 4,4-dimethylsterol fractions were separated from the unsaponifiables of 20 vegetable oils by preparative thin layer chromatography, and their compositions were determined by gas liquid chromatography. Tentative identification of the individual components of these fractions was carried out by gas liquid chromatography and combined gas liquid chromatography-mass spectrometry. Among 4-monomethylsterols, obtusifoliol, gramisterol, and citrostadienol occur abundantly in most of the oils. Cycloeucalenol also occurs in some of the oils as a major component of 4-monomethylsterols. Other 4-monomethylsterols tentatively identified are: lophenol, 31-norlanosterol, 31-norcycloartenol, and 31-norlanostenol and/or 4alpha-methylzymostenol. Among 4,4-dimethylsterols, cycloartenol and 24-methylenecycloartanol followed by beta-amyrin and cycloartanol are common to most of the oils. Butyrospermol, alpha-amyrin, lupeol, and cyclobranol together with a 4,4-dimethylsterol, presumably lanostenol, occur in some of the oils. Cyclolaudenol is present in poppy seed oil. Besides these compounds, each of the oils contains some unidentified members of 4-monomethylsterols and 4,4-dimethylsterols. The methylsterol fraction of capsicum seed oil as compared with that of the other oils is characterized by its very high content of lophenol and cycloartanol together with three other members, presumably 31-norlanostenol, 4alpha-methylzymostenol, and lanostenol.     

Investigation of oil palm based Kraft and auto-catalyzed organosolv lignin susceptibility as a green wood adhesives

The aim of this study is to highlight the application and potentiality of oil palm based lignins in the synthesis of green phenolic resins. The delignification processes were conducted using Kraft and auto-catalyzed ethanol–water pulping processes. The extracted lignins were characterized using elemental analysis, Fourier transform-infrared, ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy, molecular weight distribution (M_n, M_w and polydispersity), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The obtained FTIR results revealed that the Kraft lignin contained substantial amounts of guaiacyl units with smaller amounts of syringyl units. The molecular weight of Kraft lignin was 1564 g mol⁻¹ which is higher than organosolv lignin at 1231 g mol⁻¹. The activated free ring position (2.99%) of Kraft lignin was comparatively higher than that of organosolv lignin (2.06%) which was measured using Mannich reactivity analysis. Thermal analysis of Kraft lignin showed higher thermal stability compared to organosolv lignin. The structural and thermal characteristics implied that Kraft lignin had higher potential for the production of green phenolic resins when compared with organosolv lignin.     

Application of ion-exclusion chromatography to alkaline pulping liquors; separation of hydroxy carboxylic acids from inorganic solids

Hydroxy carboxylic acids were separated from inorganic solids on a pilot-plant scale by using columns containing a strongly acidic polystyrene cation exchange resin with bed volumes of about 1000 and 200 dm³. The liquor samples were obtained from soda–anthraquinone pulping of pine wood and they were first acidified with sulfuric acid to precipitate most of the lignin and to liberate the hydroxy acids. Under appropriate conditions, using warm water (65°C) as eluent, the liquor sample could be resolved into two distinct fractions consisting mainly of hydroxy acids and sodium sulfate, respectively. This separation method seems promising as a complementary technique in connection with the recovery of aliphatic carboxylic acids from kraft black liquors, although further studies are required to optimize the conditions.     

Use of organosolv lignin in phenol–formaldehyde resins for particleboard production: I. Organosolv lignin modified resins

This paper describes the work considering the potential for partially replacing phenol with organosolv lignin in phenol–formaldehyde resin used as an adhesive in the production of particleboard. Lignin-based resins were synthesised with organosolv lignin using various percentages of lignin replacement for phenol. The lignin was introduced to the resin in two different ways. The first method was the replacement of a certain percentage of phenol (5–40%) with lignin (as supplied) directly into resins. In the second method, lignin was modified by phenolation prior to resin manufacture. Different degrees of phenol substitution (20–30%) were investigated for the production of lignin-based resins. The physical properties of the formulated resins were measured and compared to commercial PF resin.     

Antifeedants in the Feces of the Pine Weevil Hylobius abietis: Identification and Biological Activity

Egg-laying females of the pine weevil, Hylobius abietis (L.), regularly deposit feces adjacent to each egg. Egg cavities are gnawed in the bark of roots of recently dead conifer trees. After egg deposition, the cavity is sealed by feces and a plug of bark fragments. Root bark containing egg cavities with feces is avoided as food by pine weevils, which indicates the presence of natural antifeedants. Here we present the first results of the isolation and chemical analyses of antifeedant compounds in the feces of H. abietis. In feeding bioassays, methanol extracts of the feces revealed strong antifeedant properties. Methanol extracts were fractionated by medium-pressure liquid chromatography and the antifeedant effects were mainly found in the fractions of highest polarity. Volatile compounds in the active fractions were identified by gas chromatography–mass spectrometry (GC–MS) and the nonvolatile compounds were characterized by pyrolysis–GC–MS. Based on mass spectra, a number of compounds with various chemical structures were selected to be tested for their antifeedant properties. Antifeedant effects were found among compounds apparently originating from lignin: e.g., a methylanisol, guaiacol, veratrol, dihydroxybenzenes, and dihydroconiferyl alcohol. A weak effect by fatty acid derivatives was found. The types of naturally occurring antifeedant compounds identified in this study may become useful for the protection of planted conifer seedlings against damage by H. abietis.