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1.
Keisuke Kojiro Tsunehisa Miki Hiroyuki Sugimoto Masamitsu Nakajima Kozo Kanayama 《Journal of Wood Science》2010,56(2):107-111
To investigate micropores and mesopores in the cell walls of dry wood, CO2 gas and N2 gas adsorption onto dry wood were measured at ice-water temperature (273 K) and liquid nitrogen temperature (77 K). CO2 gas adsorption isotherms obtained were used for determining micropore volumes smaller than 0.6 nm by the HK method (Horvath-Kawazoe
method), and N2 gas adsorption isotherms obtained were used for determining the mesopore volume between 2 nm and 50 nm by the Barrett-Joyner-Halenda
(BJH) method. Micropores and mesopores existed in cell walls of dry wood, and the cumulative pore volume was much larger for
micropores than for mesopores. Micropores in the cell wall of dry wood decreased with elevating heat treatment temperature,
and the decreased micropore was reproducible by wetting and drying. Mesopores did not decrease so much with elevating heat
treatment temperature. Micropore volumes for the softwood Hinoki and the hardwood Buna were compared. A larger amount of micropores
existed in hardwood Buna than in softwood Hinoki, and this relationship was considered to correspond to the difference in
thermal softening properties for lignin in water-swollen Hinoki and Buna. This result probably indicates that micropores in
the cell walls of dry wood relate to the structure of lignin. 相似文献
2.
To investigate the influence of heating and drying history on the microstructure of dry wood, in addition to the dynamic viscoelastic
properties, CO2 adsorption onto dry wood at ice.water temperature (273 K) was measured, and the micropore size distribution was obtained
using the Horvath-Kawazoe (HK) method. Micropores smaller than 0.6 nm exist in the microstructures of dry wood, and they decreased
with elevating out-gassing temperature and increased again after rewetting and drying. Dry wood subjected to higher temperatures
showed larger dynamic elastic modulus (E′) and smaller loss modulus (E″). This is interpreted as the result of the modification at higher temperature of the instability caused by drying. Drying
history influenced the number of micropores smaller than 0.6 nm in dry wood not subjected to high temperature, although the
difference in the number of micropores resulting from the drying history decreased with increasing out-gassing temperature.
A larger number of micropores smaller than 0.6 nm exist in the microstructure of dry wood in more unstable states, corresponding
to smaller E′ and larger E″ than in the stable state. Consequently, unstable states are considered to result from the existence of temporary micropores
in the microstructures of dry wood, probably in lignin.
Part of this report was presented at the 55th Annual Meeting of the Japan Wood Research Society, Kyoto, March 2005, and at
the 56th Annual Meeting of the Japan Wood Research Society, Akita, August 2006 相似文献
3.
To clarify the role of lignin in the affinities of acetylated wood for organic solvents, the effects of delignification on
the solvent adsorption of acetylated wood were investigated. Acetylated wood meals rapidly adsorbed organic solvents that
were hardly adsorbed by unmodified wood. For nonpolar and low-polarity organic solvents, a clear positive correlation was
observed between the amount of adsorption and the lignin content. This indicated that acetylated lignin was responsible for
the excellent affinities of acetylated wood for hydrophobic organic solvents. On the other hand, for lower alcohols and water,
the amount of adsorption reduced with an increase in the lignin content. It was suggested that the adsorption of such polar
solvents was dominated by insufficiently acetylated hydrophilic polysaccharides. 相似文献
4.
Umi Hamidah Takuya Arakawa Yin Ying H’ng Akiko Nakagawa-izumi Masanori Kishino 《Journal of Wood Science》2018,64(2):149-156
In this work, pretreatment of wood meals using a recycled ionic liquid (IL), 1-ethyl-3-methylimidazolium acetate ([Emim]Ac), enhanced glucose liberation by enzymatic saccharification, without dissolution of cellulose and lignin. In contrast, previous studies on IL pretreatment have mostly focused on lignocellulosic dissolution to regenerate cellulose and removing lignin. Softwood (Cryptomeria japonica) was pretreated with [Emim]Ac at 60–100 °C for 2–8 h without collecting regenerated cellulose. The pretreatment did not have a strong effect on wood component dissolution (weight of residues: 91.7–98.8%). The residues contained relatively high amounts of lignin (26.6–32.6%) with low adsorption of [Emim]Ac (0.9–2.7%). Meanwhile, the crystallinity index (C r I) of cellulose in the wood was significantly reduced by pretreatment, from 50.9% to 28.4–37.1%. In spite of the high lignin contents in the residues, their glucose liberation values by enzymatic saccharification using a cellulase mixture were 3–16 times greater than that of untreated wood. A good correlation was found between the saccharification effectiveness of pretreated samples and the C r I. Although lignin dissolved in [Emim]Ac continued to accumulate after repeated use of [Emim]Ac, the pretreatment was found to be effective for three consecutive cycles without the need to remove the dissolved materials. 相似文献
5.
Ulla Westermark 《Wood Science and Technology》1985,19(4):323-328
Summary It has been found that the lignin in a middle lamella fraction isolated by a sieving technique has the same reactivity to bromine as the whole wood lignin. A plataue value of 1 mole bromine/mole C9-unit was obtained for both samples. The lignin in compression wood had a considerably lower reactivity to bromine than the normal wood lignin. A plataue value of 0.68 mole bromine/mol C9-unit was obtained with such lignin. The discrepancy between this and earlier results from the bromination of middle lamella and the implication of the results for lignin determination by the SEM- and TEM-EDXA technique are discussed. 相似文献
6.
木材在毛细与非毛细管方向的吸收特征及受液体性质影响的研究 总被引：1，自引：1，他引：0
分别应用水、甲酰胺和二碘甲烷3种不同性质的液体,研究木材吸收液体的动力学过程及在毛细管和非毛细管2个方向的不同吸收特征。结果表明:木材吸收液体过程无论在毛细还是非毛细管方向都为三段式进行,其特征是初始和最后阶段为线性吸收,即具有零级动力学吸收的特征;而中间阶段则具有复杂的一级和二级吸收反应动力学的特征。根据吸收现象分析,液体的粘度、极性及Lewis酸碱反应性都将影响木材的吸收过程。根据所记录的动态吸收曲线,文中给出了木材吸收液体的动力学模型及参数。 相似文献
7.
Summary The formation of lignin in the cell wall of compression wood of Pinus thunbergii was examined by selective radio-labeling of specific structural units in the lignin and visualization of the label in the different morphological regions by microautoradiography. Deposition of lignin in the tracheid cell wall of compression wood occurred in the order: p-hydroxyphenyl, guaiacyl and syringyl lignin, which is the same order as observed in normal wood. However, the period of lignification in the compression wood was quite different from those of normal and opposite woods. The p-hydroxyphenyl units were deposited mainly in the early stage of cell wall formation in compound middle lamella in normal and opposite woods, while in compression wood, they were formed in both the compound middle lamella and the secondary wall. The most intensive lignification was observed during the formation of the S2 layer, proceeding from the outer to inner S2 layers for a long period in compression wood. In the normal or opposite woods, in contrast, the lignification became active after formation of S3 had begun, then proceeded uniformly in the secondary wall and ended after a short period.A part of this report was originally presented at the 1989 International Symposium on Wood and Pulping Chemistry at Raleigh, NC, U.S.A. 相似文献
8.
Haruna Aiso-Sanada Futoshi Ishiguri Denny Irawati Imam Wahyudi Shinso Yokota 《Journal of Wood Science》2018,64(6):872-879
This study investigated the anatomical and chemical characteristics of the reaction wood of a gymnpsperm species, Gnetum gnemon, and discussed on contributing factor for the type of reaction wood in this species. Cell morphology, microfibril angle (MFA) of the S2 layer and lignin distribution in secondary walls of tracheary elements, and lignin content were examined on three branches. Observations included no G-layer formation, significant decreases in vessel frequency, and altered MFA, and visible-light absorbance after lignin colour reactions in tracheid and fiber tracheid walls on the upper side in almost all samples. These results suggest that reaction wood in G. gnemon was similar to that in ‘tension-wood-like-reaction wood’ in angiosperms. On the other hand, reaction wood showed decrease in the lignin concentration in the fiber tracheid walls compared to the tracheid walls. In addition, the lignin in the tracheid and fiber tracheid walls was originally rich in syringyl units, suggesting that changes in the anatomical and chemical characteristics of secondary xylem due to reaction wood formation might relate to the ratio of the syringyl to guaiacyl units in lignin in the cell walls which function for mechanical support. 相似文献
9.
杨木应拉木微区结构可视化及化学成分分析 总被引：1，自引：0，他引：1
木材微区结构与木材宏观性质密切相关,杨木应拉木与对应木宏观性质存在较大差别,探究杨木应拉木和对应木微区结构和化学成分,可为了解杨木应力木的宏观性质提供理论根据。借助光学显微镜、荧光显微镜、显微拉曼成像光谱仪、透射电镜对杨木应拉木微区结构进行可视化研究,并借助X射线衍射技术和美国可再生能源实验室方法,分析杨木应拉木的微晶尺寸、结晶度以及化学成分。结果表明:杨木应拉木中应拉区和对应区纤维细胞微区结构差异显著。光学显微镜下显示应拉区木纤维中胶质层清晰可见,荧光显微镜和拉曼显微镜下显示胶质层的木质素浓度比对应区低。透射电镜下显示应拉区木纤维细胞壁结构由初生壁、次生壁和胶质层组成,未见次生壁外层,各层的平均厚度分别为0.61,1.22和2.53μm。对应区木纤维为典型的初生壁和次生壁结构,次生壁各层平均厚度分别为0.33,2.28和0.14μm。杨木应拉区纤维素含量(58.91%)比对应区(41.53%)高,木质素含量和半纤维素含量均比对应区的低,应拉区木质素和半纤维素含量分别为21.99%和12.01%,对应区分别为28.10%和17.08%。杨木应拉区结晶度(48.06%)比对应区(41.01%)高,应拉区晶区宽度为2.66 nm,长度为8.84 nm;对应区晶区宽度为2.65 nm,长度为9.87 nm。 相似文献
10.
Masahiko Kobayashi Toshiyuki Asano Mikio Kajiyama Bunichiro Tomita 《Journal of Wood Science》2005,51(4):348-356
The effects of ozone treatment were investigated to improve the process of liquefaction of wood with polyhydric alcohol solvents. The liquefied wood having a high wood to polyhydric alcohol ratio (W/P ratio) could be prepared by using the wood treated with ozone in the liquid phase. The liquefied wood with a W/P ratio of 2 : 1 had enough fluidity to act as a raw material for chemical products. To get some information about the effects of ozone treatment toward the wood components, cellulose powder and steamed lignin were treated with ozone and liquefied. In particular, ozone treatment in the liquid phase was found to be effective for wood and cellulose powder. On the other hand, steamed lignin self-condensed during liquefaction after treatment with ozone in the liquid phase. Thus, ozone treatment provided lignin with reactive functional groups, and caused the subsequent condensation reaction. Although lignin was converted to a more condensable structure by ozone treatment, the condensation reaction was found to be suppressed for wood during its liquefaction. The wood liquefied products displayed good solubilities in N,N-dimethyl formamide (DMF) even after treatments of long duration. It was suggested that one of the main effects of ozone treatment toward wood was the decomposition of cellulose.Part of this report was presented at the 53rd Annual Meeting of the Japan Wood Research Society, Fukuoka, April 2003 相似文献
11.
Wood, macromolecular and simple model compounds, were reacted with CrO3 or K2CrO4 aqueous solutions. Extracted lignin, guaiacol, vanillin, vanillyl alcohol and homovanillyl alcohol were chosen as model compounds for lignin, whilst cellulose, gum Ghatti, xylan, extracted hemicellulose from pine, methyl-β-D-glucopyranoside and methyl-β-cellobioside were used as models for wood polysaccharides. The kinetics of the reduction reactions of Cr(VI) were monitored using UV-Vis spectroscopy and the results obtained for several temperatures are discussed. In general terms, wood, lignin and lignin model compounds reduced Cr(VI) faster and to a greater extent than polysaccharides or simple sugar molecules. Moreover, lignin model compounds were reduced even faster than lignin. Simple sugars showed a reduction pattern similar to that of cellulose. Extracted hemicellulose revealed to be a poorer reductant while gum Ghatti was the strongest among the polysaccharides. As expected, CrO3 aq. behaved as a more powerfull oxidant than K2CrO4 aq. for these substances. Even at 100 °C, sugars or polysaccharides did not seem to be oxidised by K2CrO4 aq. 0.01 M. These results suggest that, because of the differences in reactivity, lignin reacts preferentially when wood is treated with Cr(VI)-containing formulations, like those which are applied in wood preservation treatments. 相似文献
12.
The aim of this study was to evaluate the chemical composition and the dynamic water vapour sorption properties of Eucalyptus pellita wood thermally modified in vacuum. For this purpose, wood samples were thermally modified in a vacuum oven at 160–240 °C for 4 h. Chemical composition were investigated by wet chemical analysis, elemental analysis, as well as Fourier transform infrared (FTIR) analysis, and dynamic water vapour sorption properties were evaluated by dynamic vapour sorption apparatus. The results showed that holocellulose and alpha-cellulose contents decreased and lignin and extractives contents relatively increased during the heat process. Elemental analysis showed a reduction in hydrogen content and an increase in carbon content. FTIR analysis indicated that the degradation of hemicellulose and condensation reactions of lignin occurred. In addition, the thermo-vacuum resulted in a reduction in the equilibrium moisture content of wood during the adsorption or desorption process. And the sorption hysteresis had a decreasing trend with increasing treatment temperature. The development of the hygroscopicity was related to the increase in the relative content of lignin, the degradation of the carbonyl groups in xylan and the loss of carbonyl group linked to the aromatic skeleton in lignin after heat treatment. 相似文献
13.
In order to examine the contribution of wood components to the acetylation of wood, we acetylated wood meal that had been
partially delignified. The results were analyzed in terms of the reaction kinetics. The first-order rate equation was successfully
adjusted to the weight gain data. The rate constant for acetylation initially increased with progress of lignin elimination
and then turned to decrease; the apparent activation energy showed the reverse tendency and ranged from about 90 to 130 kJ/mol.
These results suggest that lignin elimination brings not only separation of lignin but also drastic change of the chemical
and/or physical structure in the residual lignin, and this affects the reactivity of wood meal as a whole. The ultimate weight
gain estimated by the regression of the rate equation showed a minimum when lignin was moderately eliminated, which was explained
in terms of enhanced reactivity of lignin and lower accessibility for holocellulose than predicted. The equilibrium moisture
content had a maximum when lignin was moderately eliminated. This tendency is the opposite of that observed for the ultimate
weight gain, and suggests that the sites for acetylation do not always correspond to those for moisture adsorption.
Part of this report was presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, August 2004 相似文献
14.
Several ionic liquids promote depolymerization of wood components, i.e., polysaccharides and lignin, into low molecular weight compounds, some of which further re-polymerize into resin-like compounds. In this study, the depolymerization/re-polymerization of wood components in ionic liquids was applied to preparation of plywoods from Japanese cedar (Cryptomeria japonica) veneers by employing ionic liquids as adhesives. The adhesive solution was prepared by mixing an ionic liquid (pyridine hydrochloride ([Py][Cl]), imidazole hydrochloride ([IM][Cl]), or 1-ethylpyridinium chloride ([EtPy][Cl])) with water and d-glucose in various weight ratios. Tensile shear test of the three-ply plywoods prepared from the veneers and the adhesive solution through hot-pressing indicated that the plywood bonded with the [IM][Cl]-based solution ([IM][Cl]/water/glucose ratio: 9/3/2) exhibited the highest strength. Scanning electron microscope observation on the plywoods suggested that the ionic liquids softened the cell walls of the probably plywood through the depolymerization/re-polymerization reactions and the cell walls were compressed during the hot-pressing process. Entwining of the compressed cell walls and van der Waals force enhanced by the compression were considered to be origins of the adhesion of the veneers. 相似文献
15.
Summary
13C CP MAS NMR spectroscopy was used to characterize the structural changes of cell wall polymers in beech wood Fagus sylvatica during drying processes. The analysis of five wood samples, namely, untreated, untreated dried, pre-treated by steam and/or
NaOH subjected to drying showed partial depolymerization of lignin component as well as the change of the ratio of the crystalline
and of the amorphous parts of cellulose as the consequence of wood pre-treatment. In addition, T1ρ(1H) relaxation times were determined in beech wood sample pre-treated with steam at 135 °C and the lignin isolated from this
sample. The magnitudes of the relaxation times were found comparable in both samples as well as in the lignin-cellulose model
compound. These unique T1ρ (1H) values indicate that spin diffusion is complete and homogeneous due to spatial proximity of spins and confirmed the formation
of lignin-cellulose complex during thermal treatment of wood.
Received 30 June 1997 相似文献
16.
The effects of temperature on mechano-sorptive (MS) creep of delignified hinoki wood (Chamaecyparis obtusa Endl.) were investigated using longitudinal (L) and radial (R) specimens during adsorption and desorption over the temperature
range of 20°–80°C. The results were compared with those of stepwise delignified specimens tested at a constant temperature
of 20°C. It was found that the effects of temperature on the MS creep of delignified specimens are more remarkable than for
untreated specimens. The tendencies of increasing MS creep with temperature, delignification, and their combination were observed.
The increase in MS creep for L specimens was relatively small and almost equal in both adsorption and desorption processes,
while for R specimens the MS creep was small in desorption, but significantly different in adsorption. In addition, good correlation
was observed between the MS coefficient (K) and instantaneous compliance (J
0). The increase in MS creep occurs as a result of temperature increase or decrease in lignin content, or their interacting
effects. However, in the case of desorption for R specimens, the increase of MS creep was unexpectedly small due to a remarkably
increased J
0.
Part of this report was presented at the 15th Annual Meeting of the Chubu Branch of the Japan Wood Research Society in Fukui,
October 2005 相似文献
17.
18.
Summary The one-electron oxidation activity of brown-rot fungi was determined by measuring ethylene production from KTBA. Ethylene
production was related to degradation of lignin, cellulose, and wood itself. Extracellular protein that catalyzed oxidation
of KTBA was isolated from wood-containing cultures. This protein required H2O2 for KTBA oxidation. It was also found to oxidize NADH, producing H2O2 via
in the presence of O2. The protein showed little phenol-oxidase activity under conditions giving high activity against KTBA. The results indicate
that partially reduced oxygen may play a role in the initial degradation of the cellulose and lignin in wood in cultures of
brown-rot fungi. 相似文献
19.
Summary By measuring the proton spin–lattice relaxation times (T1H) in the solid-state for black spruce softwood, the molecular mobilities of carbohydrates and lignin have been evaluated as
a function of pH. These studies have shown that the mobility of the polymeric constituents of wood is affected by the ionization
of the different functional groups at different pH's. The analyses of the proton-spin–lattice relaxation time data at constant
humidity revealed that the maximum T1H for both carbohydrates and lignin occurs at about neutrality, while it was found to be depressed at the two extremes of the
pH range. By treating a wood sample with propylene oxide, the esterification of the acid groups was affected, thus deactivating
the ionization process and their contribution to T1H. The experimental T1H values for cellulose and lignin after the esterification were significantly decreased at pH 6 confirming that their ionization
plays a very significant role in determining chain mobility.
Received 1 December 1998 相似文献