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《Journal of Analytical and Applied Pyrolysis》2007,78(2):233-242
Biobleaching studies using laccase mediator system (LMS) were carried out, under optimized conditions, on two unbleached Eucalyptus globulus kraft pulps, one produced by conventional way, with kappa number of 16.1, and another with kappa number of 14.5, obtained by modified kraft procedure with a high liquor/wood ratio and with black liquor replacement in the middle of the cooking. The pulp properties before and after LMS and alkaline extraction were evaluated in terms of kappa number, hexeneuronic acid content, viscosity, brightness and acid insoluble lignin content.The original milled wood sample and the kraft pulps were characterized by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetry/mass spectrometry (TG/MS). Eucalypt wood lignin produces guaiacol and syringol derivatives during pyrolysis. These lignin products can be detected with high sensitivity using the selected ion chromatograms even in the bleached pulp of low lignin content (about 0.5%). Py-GC/MS revealed that the lignin moieties were similarly altered during biobleaching as during pulping, which is exemplified by the preferential removal of aldehyde groups from the alkyl side groups. Semi-quantitative analysis of the pyrograms indicates that the lignin content of the biobleached pulps is reduced by about half in comparison with the unbleached pulps. The TG/MS results show that the hemicellulose content of wood was strongly modified during pulping resulting in higher thermal stability. 相似文献
3.
R. A. D. Mbachu R. St. John Manley 《Journal of polymer science. Part A, Polymer chemistry》1981,19(8):2079-2089
Solvent-extracted spruce wood meal was ozonized in 45% aqueous acetic acid at room temperature. The ozone-treated wood meal was then extracted with dilute alkali at 65°C for 1 h. Lignin, α-cellulose, and hemicellulose content and the viscosities of the pulped wood-meal samples were measured as a function of the time of ozonization. Results indicate that although the attack on the wood components by ozone is not selective in this medium cellulose and hemicelluloses are degraded slowly compared with lignin. Lignin degraded approximately four times faster than the carbohydrates. At the fiber liberation point the pulp retained 78% of the original hemicelluloses and about 90% of the α-cellulose compared with 25% of the lignin. The pulp samples obtained during ozonization of the wood meal showed a slow decrease in the average degree of polymerization (DP); the limit reached near 350 was attributed to the inaccessibility of the ordered regions in native cellulose to ozone. 相似文献
4.
Marcelo Coelho dos Santos Muguet Kyösti Ruuttunen Anna-Stiina Jääskeläinen Jorge Luiz Colodette Tapani Vuorinen 《Cellulose (London, England)》2013,20(5):2647-2654
The objective of this study was to evaluate the influence of autohydrolysis on mechanical defibration of Eucalyptus wood chips. The autohydrolysis process changed notably the mechanical properties of Eucalyptus chips. The removal of mainly hemicelluloses undoubtedly decreased the overall pulp yield. Hemicellulose losses cannot be solely accounted for the changes in the wood and pulp properties, because the autohydrolysis also caused changes in lignin. When comparing the mechanical pulp fibers of the original wood chips with the fibers resulting from the autohydrolyzed wood material, it was clear that the rupture point shifted from the secondary wall to the middle lamella, confirmed by X-ray photoelectron spectroscopy measurements. This study revealed the mechanical behavior of autohydrolyzed wood chips and can provide useful information for integration of mechanical pulp mills into the biorefinery concept in the future. 相似文献
5.
Amin Ibrahim Philip B. Oldham Terrance E. Conners Tor P. Schultz 《Microchemical Journal》1997,56(3):393-402
FT-Raman spectroscopy is used for the rapid measurement of wood pulp lignin. A total of 23 western softwood pulp samples with known kappa numbers (10–38) are used. Each sample is divided into three portions and scanned separately. The integrated area of the lignin band at approximately 1600 cm−1is ratioed against the integrated area of the cellulose bands in the 1200–1010 cm−1region and correlated to known kappa numbers. The measured ratios behave linearly with the kappa number (r= 0.99) and can be reproducibly determined with an error of approximately 2% or less. The data are presented and discussed in view of the potential for at-line analysis of lignin associated with chemical delignification of wood pulp. 相似文献
6.
Based on results from 2D NMR studies, both pinoresinol and secoisolariciresinol structures were found to be present in native lignin from spruce wood as well as in spruce kraft lignin and residual kraft pulp lignin. These two structures constitute the major types of beta-beta inter-unit linkages present in spruce lignin, but their formation in the lignin polymer may follow different pathways leading to their different bonding patterns with the rest of the lignin polymer. The mechanisms involved are discussed. 相似文献
7.
《Journal of Analytical and Applied Pyrolysis》2009,86(1-2):19-29
This study centred on the analysis of lignin in situ of cloned eucalypt and pine kraft pulps. Trametes versicolor laccase-violuric acid system (LMS) delignifications were performed on a softwood (Pinus pinaster) and a hardwood (Eucalyptus globulus) conventional kraft pulp with an initial kappa number of 34.5 and 15.5, respectively. The LMS treated pulps were then subjected to alkaline extraction stages (E). The kappa number data show that LMS is effective at biodelignifying both softwood and hardwood kraft pulps. However, under the conditions employed in this study, a greater level of biodelignification was obtained with LMS E. globulus (hardwood) than with LMS P. pinaster (softwood), but the amount of lignin removed was higher for the softwood pulp. The original milled wood samples, kraft pulps, biodelignified kraft pulps, and isolated residual lignin and milled wood lignins from the two wood samples have been characterized by pyrolysis-gas chromatography/mass spectrometry. The analysis of the pyrograms indicates that the lignin compositions of the two wood species and corresponding pulps are very different, as expected; however, the knowledge of the chemical mechanisms of delignification is very limited and requires additional work. Analytical pyrolysis is one the few degradative methods for the analysis of biopolymers that has shown a sufficient degree of success. 相似文献
8.
Investigation of the chemical modifications of beech wood lignin during heat treatment 总被引:3,自引:0,他引:3
Nicolas Brosse Roland El Hage Mounir Chaouch Mathieu Pétrissans Stéphane Dumarçay Philippe Gérardin 《Polymer Degradation and Stability》2010,95(9):1721-1528
Holocellulose, Klason lignin and milled wood lignin (MWL) of beech wood were extracted before and after heat treatment and analysed using CP MAS 13C NMR, 13C NMR, 31P NMR and size exclusion chromatography (SEC). Experimental results showed that the thermal treatment degrades hemicelluloses and affects lignin polymer through depolymerisation due mainly to cleavage of β-aryl-ether linkages and recondensation reactions. The spectroscopic analysis of MWL demonstrated that these recondensation reactions involved mainly guaiacyl units through formation of 5,5′-biphenolic and diarylmethane structures.Analysis of molecular weight distribution of MWL by SEC indicated that average molecular weights of heat treated milled wood lignin were lower than those of native milled wood lignin. 相似文献
9.
K.K. Kesari M. Leppänen S. Ceccherini J. Seitsonen S. Väisänen M. Altgen L.-S. Johansson T. Maloney J. Ruokolainen T. Vuorinen 《Materials Today Chemistry》2020
Understanding the ultrastructure and chemical characterization of pulp fibers is highly important in utilizing wood as a raw material in a wide scope of applications, such as forest biomass-based biorefineries and low-cost renewable materials. The observation of the ultrastructure is not possible without advanced microscopy and spectroscopy techniques. Therefore, this study focuses on exploring the ultrastructure of pulp fibers with helium ion microscopy (HIM) and scanning electron microscopy (SEM). For the analysis of chemical characterization in the pulp fibers, Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) were performed. For these studies, the pulp fiber samples were obtained mainly from three different wood species, i.e. spruce, birch and eucalyptus. They were received in the never dried state and dried with a critical point drier (CPD) to minimize pore collapse. The spectroscopy results showed a strong signal from crystalline cellulose and confirmed the absence of lignin after Kraft pulping and bleaching. However, with XPS about 2% of lignin was detected in eucalyptus pulp. The results obtained with the microscopy techniques are compared and indicating the nanofibril size, shape, surface roughness as well as their orientation in pulp fibers. To our knowledge, this is the first time that HIM is applied to study the ultrastructure of pulp fibers and compared against more conventional microscopy and spectroscopy techniques. The main differences between HIM and SEM were found to be related to the focusing and magnification. The individual nano- and microfibrils as well as their bundles were more easily visible with HIM than with SEM. Also, with HIM it was possible to get the total area in focus at once which was not the case with SEM. The increased understanding of the ultrastructure and chemical composition of wood pulp enhance the development of novel wood-based products and processes for their manufacture. 相似文献
10.
SUN Hui XU Ying-kai XU Guo-zhi 《高等学校化学研究》2010,(3):488-490
In an effort to utilize NMR technique for the analysis of the structural components of wood and biomasses such as lignin, we made a comparative study of lignin contents of several types of lignocellulosic materials both before and after enzymatic hydrolyses. To this end, Eucalyptus Globulus, Norway spruce thermomechanical pulp(TMP) corn stover and Eucalyptus kraft pulp were ball-milled and treated with cellulase to prepare materials with high lignin contents. These materials were analyzed via 31P NMR in ionic liquids. The results show that the contents of various functional groups for the lignocellulosic materials after enzymatic hydrolyses are generally in agreement with those from their corresponding enzymatic mild acidolysis liginins(EMALs), indicating that 31P NMR analysis of lignocellulosic materials in ionic liquids is a promising method for quantitative characterization of lignocellulosic materials. 相似文献
11.
When pine wood decayed by white- and brown-rot fungi was observed in TEM after fixation and staining with glutaraldehyde/osmium
tetroxide/ uranylacetate and embedding in Spurr’s ultralow viscosity resin electron dense particles, called “osmiophilic particles,”
a typical distribution for the two decay types could be observed: in white-rotted wood the particles could be found in and
around the hyphae and on the lumen surface of the wood cell wall, mostly aggregated to thick clusters. During the whole course
of decay the wood cell walls were free of the particles, but they were present on the corroded surfaces. In brown-rotted wood
the “osmiophilic particles” also could be found in and around the hyphae, but in contrast the particles were distributed over
all the wood cell wall layers from the early to late stages of decay.
The distribution of the “osmiophilic particles” coincides with the place where the major cell wall degradation takes place:
in white-rot the cell walls are degraded from the lumen to the middle lamella; in brown-rot a depolymerization and degradation
of the carbohydrates takes place all over the wood cell wall. Since the “osmiophilic particles” can be found where the degradation
takes place, it can be concluded that they are causally connected with wood decay.
The fact that they also were found in, and some of them also around, hyphae grown on malt-agar or Sabouraud-dextrose-agar
proves that they are produced by the fungi and cannot be degradation products.
The possibility that they could be preparative artifacts can be excluded because uncolonized wood was free of “osmiophilic
particles.”
Since the “osmiophilic particles” are produced by the fungi and can be found in places where wood is decaying, it can be further
concluded that they are a fungal agent that is involved in wood degradation, probably fungal enzymes. The observation that
the large “osmiophilic particles,” which may have a size of up to 20 nm, are composed of globular subunits of a diameter of
2—3 nm also speaks for their enzymatic nature.
To find out which type of enzyme they might be, the white-rot fungusTrametes hirsuta was grown on wood pulp with 7% lignin, on delignified wood pulp containing cellulose and hemicellulose, and on filterpaper
(pure cellulose). The hyphae on wood pulp containing 7% lignin were surrounded by thick sheaths of “osmiophilic particles,”
whereas with the hyphae grown on delignified wood pulp and pure cellulose only a few particles could be found. This makes
it clear that the production of the “osmiophilic particles” is induced by lignin. 相似文献
12.
Nyok-Sai Hon 《Journal of polymer science. Part A, Polymer chemistry》1975,13(12):2641-2652
The effect of lignin on free-radical formation in photoirradiated pulp was studied by means of electron spin resonance spectroscopy. Samples were irradiated with light of wavelength longer than 3400 Å as well as longer than 2537 Å. Radical formation in aspen lignin was observed before and after irradiation with light of wavelength longer than 3400 Å. Upon irradiation, free radicals were formed in a pulp sample with 0% lignin content only when oxygen was present. On irradiation with light longer than 2537 Å, in the presence of nitrogen, oxygen, and under vacuum, free-radical formation was found in all cases. The largest concentration of radicals was obtained under vacuum, the smallest in oxygen. It is evident that cellulose was protected from radiation by the presence of lignin. Increased aspen lignin content in pulp led to a decrease in the relative signal intensity of ESR spectrum, that is, a decrease of the yield of free radicals in the cellulose fraction in pulp. Irradiation with light in the presence of oxygen caused significant yellowing of the pulp sample, and these photooxidation and discoloration reactions occurred primarily on the surface of the sample irradiated. 相似文献
13.
A. Pizzi 《Journal of polymer science. Part A, Polymer chemistry》1982,20(3):707-724
The kinetic behavior of a Cr6+/Cu2+ system in its reaction with wood has been elucidated. The same reactions with carbohydrates and lignin of wood for CrVI alone are still present. Approximately 20% of the copper is fixed to the guaiacyl units of lignin in the form of copper chromate; the remaining copper forms complexes with cellulose and mainly with the guaiacyl units of lignin. The CrVI/lignin guaiacyl unit complexes already found for the treatment of wood with CrO3 are still the main CrVI complexes formed. Copper chromate is present as [Cu(H2O)2(guaiacol)]CrO4(guaiacol) complexes, and CuCrO4 bridges between different guaiacyl units of the lignin network appear to be likely. Substantial interference of the Cu2+ ions in the second-zone reactions of CrVI with wood occurs. The amount of CrVI and CrIII fixed onto lignin and cellulose compares well with experimental values. Rate constants, energies of activation, and Arrhenius equations of the various reactions have been obtained. The amount of Cu2+ interference in the reaction has also been calculated. 相似文献
14.
L. V. Kanitskaya S. A. Medvedeva V. A. Babkin D. F. Kushnarev G. A. Kalabin 《Chemistry of Natural Compounds》1994,30(4):505-514
The lignin of mechanically ground aspen wood and lignins isolated from aspen wood attacked by the fungusPhanerochaete sanguinea have been investigated by quantitative1H and13C NMR spectroscopies. It has been shown that the biodestruction of the lignin takes place through the cleavage of alkyl-aryl and aryl-aryl bonds and is accompanied by demethylation (demethoxylation) reactions, and the oxidation of Cα and Cγ atoms. In addition to reactions in which the C—C bonds are cleaved, the formation of ether bonds has been observed. An interconnection has been shown between the variations in the amount of functional groups, fragments, and the bonds in biolignins and the loss in mass of the wood. A method is proposed for evaluating the carbohydrate content in lignin preparations using the NMR method. 相似文献
15.
Pallavi Dwivedi V. Vivekanand Nidhi Pareek Amit Sharma Rajesh P. Singh 《Applied biochemistry and biotechnology》2010,160(1):255-268
Mixed enzyme preparation having both xylanase and laccase activity was evaluated for its bleach enhancing ability of mixed
wood pulp. The enzyme was produced through co-cultivation of mutant Penicillium oxalicum SAUE-3.510 and Pleurotus ostreatus MTCC 1804 under solid-state fermentation. Bleaching of pulp with mixed enzyme had resulted into a notable decrease in kappa
number and increased brightness as compared to xylanase alone. Analysis of bleaching conditions had denoted that 8 IU g−1 of mixed enzyme preparation (xylanase/laccase, 22:1) had led into maximal removal of lignin from pulp when bleaching was
performed at 10% pulp consistency (55 °C, pH 9.0) for 3 h. An overall improvement of 21%, 8%, 3%, and 5% respectively in kappa
number, brightness, yellowness, and viscosity of pulp was achieved under derived bleaching conditions. Process of enzymatic
bleaching was further ascertained by analyzing the changes occurring in polysaccharide and lignin by HPLC and FTIR. The UV
absorption spectrum of the compounds released during enzymatic treatment had denoted a characteristic peak at 280 nm, indicating
the presence of lignin in released coloring matter. The changes in fiber morphology following enzymatic delignification were
studied by scanning electron microscopy. 相似文献
16.
Very high yield sulphite pulps were produced by cooking black spruce wafers in pulping liquors at pH 7 or 10, containing 0.1% (on O.D. wood) of soluble anthraquinone (SAQ). These pulps had better strength properties relative to controls prepared without SAQ, breaking length and burst index being greater, on average, by 20%. Other improvements included: increased pulping rate, lower lignin contents at comparable pulp yields, and higher carbohydrate content at the same level of residual lignin in pulp (this resulted in an increase of total pulp yield by 2%). Results of cooks in liquors ranging in pH from 4 to 10, and under variable conditions of time (20–60 min) and temperature (120–160°C) suggested that: firstly, AQ does not act as a pulping catalyst at pH 4, and secondly, the sulphonate contents of AQ-catalyzed pulps are lower than those of the uncatalyzed controls. In the light of the lower sulphonate content, the higher strength is unexpected. 相似文献
17.
A. Pizzi 《Journal of polymer science. Part A, Polymer chemistry》1982,20(3):739-764
The kinetic behavior of copper–chromium–arsenic (CCA) wood preservatives in their reaction with wood, lignin, cellulose, and their respective simple model compounds, guaiacol and D(+)-glucose, has been elucidated. Copper chromatesVI/lignin guaiacyl units and chromiumIII arsenates/lignin guaiacyl units, which are stable and insoluble complexes formed during the reaction, have been characterized. No copper arsenates were formed during the reactions (which were carried out using a CCA of type C). The sequence, nature, and combined effect of the reactions of CCA with wood, lignin, and cellulose are similar to that already described for the “CrO3 alone,”1 Cu/Cr2, and Cr/As3 systems. Rate constants, energies of activation, and Arrhenius equations have been obtained and reported. The distribution of CrVI, CrIII, Asv, and Cu2+ in CCA-C-treated wood has been calculated. The results obtained have allowed meaningful comparisons of several commercial CCA formulations. 相似文献
18.
Thermochemical reactions occurring in various stages of structural transformations of native lignin in its thermal treatment
in a wide temperature range are considered and classified. Attention is given to the initial state of lignin in its primary
isolation without heating. The terminology of lignin products, used in the literature, is put in order to a certain extent.
The thermochemical reactions in which lignins are transformed in processing of raw wood materials and the structure of isolated
lignins undergoes changes in the course of the target thermal treatment are differentiated. The applied aspect of the directed
thermochemical synthesis of new lignin-based low- and high-molecular-mass compounds is discussed. 相似文献
19.
W. M. G. N. Van Loon A. D. Pouwels P. Veenendaal J. J. Boon 《International journal of environmental analytical chemistry》2013,93(2):255-264
Abstract Investigations on the effluent of a German pulp mill on the river Rhine using ultrafiltration and pyrolysis gas chromatography mass spectrometry have shown the presence of several chlorinated 2-methoxyphenols, which probably originate from chlorinated lignin or lignosulfic acid. Chlorinated phenolic pyrolysis products identified were 2-methoxy-6-chlorophenol, 2-methoxy-4-methyl-6-chlorophenol, 2-methoxy-dichlorophenol, 2-methoxy-4-vinyl-6-chlorophenol, 2-methoxy-4-(chloropropyl)phenol, 2-methoxy-4-(prop-2-enyl)-6-chlorophenol, 2-methoxy-4-(propan-2-one)-6-chlorophenol, 2-methoxy-3, 5, 6-trichlorophenol, 2-methoxy-4-vinyl-3, 5, 6-trichlorophenol. Monochlorinated 2-methoxyphenols were the dominant chlorinated pyrolysis products, smaller amounts of di- and trichloromethoxyphenols were also detected. 2-Methoxyphenols (guaiacols) were the dominant lignin pyrolysis products, only small amounts of 2, 6-dimethoxyphenols (syringols) were detected. This indicates the origin from soft wood. A Py-(GC)-(MS)-TIC-chromatogram of reference spruce milled wood lignin is comparable with the TIC-chromatogram of pulp mill effluent MW-fraction > 10,000, showing many similar compounds. The ultrafiltration fraction 1000 < MW < 10,000 showed a remarkably empty TIC-chromatogram, with 2-methoxyphenol and 2-methoxy-6-chlorophenol as the only significant phenolic peaks. This may indicate a high degree of oxidation/chlorination of lignin in this fraction. 相似文献
20.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1993,49(5-6):819-829
The use of near-infrared (NIR) Fourier transform (FT) Raman spectroscopy for the study of lignocellulosic materials is discussed. An application utilizing NIR FT-Raman spectroscopy to study a novel chlorine-free process for the bleaching of wood pulps is presented in detail. The new process, still under development, entails the oxidation of residual lignin in wood pulps by vanadium-substituted polyoxometalates, and reoxidation of the reduced polyoxometalates by chlorine-free oxidants such as air, dioxygen, peroxides or ozone. Results from FT-Raman measurements of polyoxometalate-treated pulps are compared with those from chemical, spectroscopic and optical techniques commonly used in the pulp and paper industry. 相似文献