Showing papers in "Journal of Wood Chemistry and Technology in 2002"
TL;DR: In this paper, the authors applied near infrared spectrometry and multivariate data analysis to predict the chemical composition and physico-chemical characteristics of eucalypt unbleached kraft pulps obtained at different laboratory pulping conditions.
Abstract: Near infrared spectrometry and multivariate data analysis were applied to predict the chemical composition and physico–chemical characteristics of eucalypt unbleached kraft pulps obtained at different laboratory pulping conditions. Viscosity, degree of polymerization (DP), kappa, brightness and contents of glucan, xylan, uronic acids, and lignin were the modeled variables using diffuse reflectance near infrared spectra obtained on pulp handsheets and the partial least squares (PLS) method. Models with two to four PLS components and good predictive ability were established after first derivative spectra pre-processing and application of cross-validation methodology. The predictive models can reduce the time consuming traditional analyses in the pulping industry laboratories, and also lead to a better process monitoring for suitable applications.
54 citations
TL;DR: In this paper, residual and dissolved lignin from different phases of kraft delignification of Eucalyptus globulus wood were isolated and characterized by 1D and 2D 1HNMR, 13C NMR, Electrospray Ionization Mass Spectrometry (ESI/MS), and gel permeation chromatography (GPC).
Abstract: Residual and dissolved lignin from different phases of kraft delignification of Eucalyptus globulus wood were isolated and characterized by 1D and 2D 1H NMR, 13C NMR, Electrospray Ionization Mass Spectrometry (ESI/MS), and gel permeation chromatography (GPC). During the temperature rise period, below 70°C, about 20% of the lignin was dissolved without significant structural changes. Above 70°C, the lignin suffered significant degradation/fragmentation in the cell wall prior to dissolution. The lignin ether-linked syringyl units were the most susceptible to alkaline degradation. Through the course of pulping, the residual lignin (RL) revealed a gradual increase of aliphatic moieties of unknown structure, as well as a decrease of native structures such as phenylcoumaran and pino-/syringaresinol lignin units. A significant decrease of the β-O-4 structures content in RL was detected only at the final cooking temperature. The lignin dissolved in the black liquor (BL) consisted of highly branched oligo...
52 citations
TL;DR: In this article, the effects of two pre-treatment processes (alkaline wet oxidation and enzyme treatment with laccase) on lignocellulosic materials for applications in particleboards and fiberboards were evaluated.
Abstract: Wheat straw (Triticum aestivum) and beech (Fagus sylvatica), were used to evaluate the effects of two pre-treatment processes (alkaline wet oxidation and enzyme treatment with laccase) on lignocellulosic materials for applications in particleboards and fiberboards. Wheat straw and beech fibers reacted differently in the two processes. The chemical composition changed little following enzyme treatment. After alkaline wet oxidation, fibers enriched in cellulose were obtained. With both materials, almost all hemicellulose (80%) together with a large portion of the lignin were solubilised by alkaline wet oxidation, but essentially all cellulose remained in the solid fraction. Following enzyme treatment most material remained as a solid. For wheat straw, reaction with acetic anhydride indicated that both treatments resulted in more hydroxyl groups being accessible for reaction. The enzyme treatment gave a more reactive surface than alkaline wet oxidation for wheat straw, whereas the opposite was obser...
39 citations
TL;DR: In this paper, the residual and dissolved lignins were isolated by soft acidolysis and acidic precipitation, respectively, and submitted to analysis of residual sugars and methoxyl groups, as well as to analysis by nitrobenzene and permanganate oxidation and thioacidolysis.
Abstract: Eucalyptus globulus wood was subjected to kraft pulping, reaching different extents of delignification. The residual and dissolved lignins were isolated by soft acidolysis and acidic precipitation, respectively, and submitted to analysis of residual sugars and methoxyl groups, as well as to analysis by nitrobenzene and permanganate oxidation and thioacidolysis. Results from both residual and dissolved lignins analyses indicated that in the initial phase of pulping there is a preferential removal of lignin enriched in guaiacylpropane (G) and p-hydroxyphenylpropane (H) units, which is highly condensed and bonded with polysaccharides, predominantly with xylan. During the bulk and residual phases of pulping, lignin enriched in syringylpropane (S) units is progressively removed, leading to the increase of S/G ratio of black liquor lignin. After a purification step of dissolved lignins, two fractions with distinct levels of carbohydrates and with different structural features were obtained. The overall...
32 citations
TL;DR: In this article, the authors introduced the Yellow Birch (Betula alleghaniensis), the emblem tree of Quebec, is commercially important and one of the most widespread birch species in the province, but the use of its bark is limited.
Abstract: Birch bark represents an abundant, and currently under-utilized, natural resource. Yellow birch (Betula alleghaniensis), the emblem tree of Quebec, is commercially important and one of the most widespread birch species in the province, but the use of its bark is limited. It is only used as a low value fuel source in solid wood products industries. Yellow birch bark triterpene constituents such as lupeol, betulin and betulinic acid have been described to have high biological activity. The yellow birch bark triterpene constituents such as betulin and certain derivatives of this natural substance have demonstrated interesting therapeutic properties. For example, betulinic acid has been shown to possess anti-tumor activity against human melanoma cells both in vitro and in vivo models. Its mechanism of action consists in the induction of apoptosis or cellular suicide in the cancer cells without affecting healthy cells.[14] These natural products confer added value to this tree. In this study, we inves...
30 citations
TL;DR: In this article, the outer bark of Betula papyrifera birch tree was separated by sublimation in a batch vacuum pyrolysis reactor in the temperature range of 250-300°C and under a total pressure of 0.7-kPa.
Abstract: Separation of betulin from the outer bark of Betula papyrifera birch tree by sublimation in a batch vacuum pyrolysis reactor was studied in the temperature range of 250–300°C and under a total pressure of 0.7 kPa. Yield of 9.5% by weight of betulin on an anhydrous bark basis was obtained. The total yield of extractives was in the range of 28–32%. The purification of betulin was achieved by solvent extraction followed by crystallization. In comparison, soxhlet extraction using dichloromethane yielded 11.5% of betulin. The structural analysis of the purified betulin has been made by GC/MS and 1H NMR.
25 citations
TL;DR: The chemical composition of three pitch samples coming from an Eucalyptus globulus ECF bleached kraft pulp mill was studied by GC-MS in this article, showing that all samples are rich in fatty acids, including several ω- and α-hydroxyfatty acids and several oxidation products of β-sitosterol.
Abstract: The chemical composition of three pitch samples coming from an Eucalyptus globulus ECF bleached kraft pulp mill was studied by GC-MS. All samples are rich in fatty acids, including several ω- and α-hydroxyfatty acids and several oxidation products of β-sitosterol, such as 5,6-epoxy-24-ethylcholestane-3-ol and 24-ethylcholestane-3,5,6-triol. One oxidation product of oleic acid, namely 9,10-dihydroxyoctadecanoic acid was also identified. The α-hydroxyfatty acids, the sterols oxidation products and 9,10-dihydroxyoctadecanoic acid are reported here for the first time as components of pitch issued from ECF bleached kraft pulp mills.
24 citations
TL;DR: In this article, the authors investigated the effect of substitution and environment on the absorption of ferulic acid and found that dehydrodiferulate type units appear to be the most likely chromophore among the ferulic acids-derived structures.
Abstract: The UV–Vis. absorption of ferulic acid and related compounds may be considerably augmented by substitution and environment. Among the circumstances investigated in the present study, esterification (mostly to polysaccharides in plant cell wall), dehydrodimerization and inclusion in a cellulose matrix substantially cause the absorption to increase and extend into the visible region. As a result of the combination of these three effects, dehydrodiferulate type units appear to be the most likely chromophore among the ferulic acid-derived structures.
22 citations
TL;DR: In this article, the production of bleached cellulose pulps from elephant grass (Miscanthus sinensis) via a two-stage soda pulping process and a TCF bleaching sequence is evaluated.
Abstract: The production of bleached cellulose pulps from elephant grass (Miscanthus sinensis) via a two-stage soda pulping process and a TCF bleaching sequence is evaluated in this work. The impregnation rapid steam pulping process (IRSP) involves impregnating of the lignocellulosic material with the pulping liquor, withdrawing the excess liquor and rapidly steaming the impregnated material at 180–200°C for a short time. In this paper the process variables and their effect on the kappa number, yield and viscosity of the unbleached pulps are discussed. Bleaching by an ozone-based TCF sequence was tested, and the papermaking properties of the bleached pulp were determined. A kappa number of 19 was obtained by impregnating at an alkali charge of 30 + 0.1% anthraquinone carboxylic acid (AQCA) and pulping at 180°C for only 15 min. Kappa was reduced to 16 by extending pulping time to 26 min. The alkali consumption during impregnation and pulping was 10.2 g NaOH/100 g of dry Miscanthus. Screened pulp yield, visc...
22 citations
TL;DR: In this paper, a novel catechinic acid stereoisomer, 6-(3,4-dihydroxyphenyl)-7,9-epoxy-9-hydroxy-bicyclo[3.3.1]nona-2,4dione was isolated from base-catalyzed reaction products of (+)-catechin at pH 12 and 40°C.
Abstract: A novel catechinic acid stereoisomer, 6-(3,4-dihydroxyphenyl)-7,9-epoxy-9-hydroxy-bicyclo[3.3.1]nona-2,4-dione was isolated from base-catalyzed reaction products of (+)-catechin at pH 12 and 40°C. The 6S absolute configuration of this compound has been confirmed from its 1H-NMR coupling constants, while the 6R configuration was previously reported for catechinic acid. The formation of a novel catechinic acid stereoisomer shows that the rearrangement of (+)-catechin to catechinic acid through the quinone–methide intermediate is not stereospecific but stereoselective.
19 citations
TL;DR: In this paper, the authors showed that 6-year-old partially CAD-deficient pine trees showed better pulp strength properties than the same age normal pine trees, which probably reflects the milder pulping conditions needed in the case of the partially CADdeficient tree.
Abstract: Mutant loblolly pine trees that are partially deficient in cinnamyl alcohol dehydrogenase (CAD) have been studied as a possible new source of pulpwood. Young (4- and 6-year-old) partially CAD-deficient pine trees are ˜20% more easily delignified (pulping and bleaching) and provide similar pulp yields to that of similarly aged normal pines grown on the same plots. Bleached pulp from a 6-year-old partially CAD-deficient pine tree displayed better strength properties than the same age normal pine tree; this probably reflects the milder pulping conditions needed in the case of the partially CAD-deficient tree. Studies also were conducted on a limited number of 14-year-old trees from a different genetic background. In contrast to the results with young trees, no real differences in ease of delignification, pulp yields, bleached pulp strength properties, and wood specific gravities were observed with the 14-year-old trees. There would likely be no penalty if partially CAD-deficient trees were used for ...
TL;DR: In this paper, binary equilibrium constants for hydrogen and metal ion exchange on carboxylate sites in bleached pulp were measured at 25°C, with log k Na/Ca = −1.633 ± 0.119, log k H/C = 0.64 ± 0., and intrinsic dissociation constant pK io of 3.46.
Abstract: Management of nonprocess element (NPE) accumulation in pulp washing operations requires equilibrium models that predict the distribution of metals between the wash liquor and the pulp fibers. The overall goal of this study was to assess models for predicting the multi-component adsorption of hydrogen ions (H+), sodium ions (Na+), and calcium ions (Ca+2) onto bleached and unbleached kraft pulp fibers over a pH range of 2.7–11. As part of this study, binary equilibrium constants for hydrogen and metal ion exchange on carboxylate sites in bleached pulp (0.041 meq/g dry pulp) were measured at 25°C, with log K Na/Ca = −1.604 ± 0.119, log K H/Ca = 0.633 ± 0.087, and intrinsic dissociation constant pK io of 3.64 ± 0.46. Ion exchange and Donnan equilibrium models adequately predicted the multi-component equilibrium data for competitive adsorption of H+, Na+, and Ca+2 onto bleached kraft wood pulp fibers. The ion exchange model was fully predictive, whereas the Donnan model required that the solution pH b...
TL;DR: In this article, the effect of the harvesting age of hemp stems on their chemical composition and the biomass produced by the plants were studied, and it was concluded that hemicellulose was a good source of long and strong fibers.
Abstract: With the increasing scarcity of available forest for harvesting, there is a potential need for alternatives to wood fibers for pulp and paper production. Hemp is considered to be a good source of long and strong fibers. In this study, the effect of the harvesting age of hemp stems on their chemical composition and the biomass produced by the plants were studied. Hemp stems were harvested at ages of 30, 60, 90, and 120 days. Standard TAPPI procedures were used for chemical analyses of the stems. There was little variation observed in the percentage of the constituents such as lignin, hemicellulose, and α-cellulose with the plant growth. However, a very significant decrease was seen in the percentages of extractives, ash, and silica with plant growth. The rate of increase of biomass was higher in the first half of the growing period, i.e., from 30 to 60 days, compared to the second half, from 60 to 90 days. On the basis of the chemical constituents and the biomass produced, it is concluded that hem...
TL;DR: In this article, the effect of chelator-mediated free radical treatment (CMT) on drainage rate, strength properties, optical properties, and fiber morphology for a fully bleached hardwood kraft pulp was investigated.
Abstract: Research was conducted into the effect of a chelator-mediated free radical treatment (CMT) on drainage rate, strength properties, optical properties, and fiber morphology for a fully bleached hardwood kraft pulp. The nature of the pulp furnish, specifically the fines and microfibril content, and its gross fiber characteristics, had a significant effect on the final fiber and paper properties. This was primarily due to an increase in the specific surface area of small fibers and fines in the beaten pulp. Treatments with high concentrations of Fenton reagents displayed severe damage to the cellulose fibers in both the beaten and unbeaten pulp. However, under relatively mild reaction conditions, fiber surface fibrillation of the unbeaten virgin fibers occurred. This observation was confirmed through results showing increased pulp tensile strength after treatment. *This is paper 2582 of the Maine Agricultural and Forest Experiment Station.
TL;DR: In this article, a new impregnation method to enhance strength properties of mechanical pulps in the absence of sulfonation treatment has been developed, which gave the treated pulps more than 20% increase in strength properties, but pulp brightness dropped.
Abstract: A new impregnation method to enhance strength properties of mechanical pulps in the absence of sulfonation treatment has been developed. Impregnation of groundwood, thermomechanical, and chemithermomechanical pulps with reactive ultra-thin film-forming silane precursors has been investigated. Silane impregnation gave the treated pulps more than 20% increase in strength properties, but the pulp brightness dropped. The effect of impregnation time and temperature were studied. It was found that silane impregnation is highly effective under ambient temperature and pressure conditions, and the efficiency increased with increasing pulp temperature. In addition, the treated pulp demonstrated its advantages over an untreated one in terms of wet-end properties. The enhanced strength properties of silane-treated pulps are possibly due to an increase in fiber-to-fiber bonding.
TL;DR: In this paper, five lipophilic extractives isolated with toluene-ethanol (2.1, v/v), chloroform, petroleum ether, dichloromethane, and hexane from rice straw were examined by Fourier transform infrared, 1H and 13C nuclear magnetic resonance spectroscopies, and thermal analysis.
Abstract: Five lipophilic extractives isolated with toluene–ethanol (2 : 1, v/v), chloroform, petroleum ether, dichloromethane, and hexane from rice straw were examined by Fourier transform infrared, 1H and 13C nuclear magnetic resonance spectroscopies, and thermal analysis. In comparison with other four extractives, the extractives, isolated with toluene–ethanol (2 : 1, v/v), showed much lower absorption bands at 2926 and 2853, and 1739 and 1713 cm−1 for CH2 and CH3 stretching frequencies, and C=O stretching in ester and acids, indicating a much lower content of the lipophilic substances in the extractives. A rather weak band at 1030 cm−1 in the extracts, isolated with petroleum ether and dichloromethane, indicated that the two extracts were relatively free of co-extracted polysaccharides. The thermal analysis showed that the melting temperatures of the extractives occurred between 57.1 and 71.4°C, indicating a mixture of the extracts.
TL;DR: In this paper, the chemical oxygen demand in the beech condensate varied from 2016 to 1393O mg/L. This value is two to three fold higher than the corresponding biological oxygen demand (BOD5).
Abstract: Beech (Fagus sylvatica L.) condensate from a steaming operation was collected and analyzed. The condensate exhibited a low pH, and contained carbohydrates and phenolic compounds. A total of five phenolic acids and aldehydes (syringic acid, vanillic acid, p-hydroxybenzoic acid, syringaldehyde, vanillin) were identified. TLC of the carbohydrates showed the presence of glucose, galactose, xylose, mannose and/or arabinose in the condensate. Fructose, saccharose, raffinose and stachyose were also identified. The COD, BOD5, pH, conductivity and suspended solids (TSS) were determined. The chemical oxygen demand (COD) in the beech condensate varied from 2016 to 1393O mg/L. This value is two to three fold higher than the corresponding biological oxygen demand (BOD5).
TL;DR: In this article, an essentially new alkaline chemical pulping process, the Quatam process, was introduced using an organic base for producing cellulose fibers from wood and annual plants.
Abstract: An essentially new alkaline chemical pulping process—the Quatam process—has been introduced using an organic base for producing cellulose fibers from wood and annual plants. Solutions of quaternary ammonium compounds, preferably tetramethylammonium hydroxide (TMAH), serve as pulping liquors. The process produces high quality pulp with low kappa number, high brightness and good viscosity—without using sulfur-containing compounds. The process is suitable for both hardwood and softwood. The pulping selectivity of TMAH is demonstrated. Bleachability and mechanical properties of the resulting pulp are compared to those of conventional Kraft pulp.
TL;DR: In this paper, light-induced aging of lignocellulosic materials has been studied with a new technique involving selectively α-, β-, and γ-13C-enriched cell wall-dehydrogenation polymers (CW-DHPs) and solid state 13C-NMR spectroscopy.
Abstract: Light-induced aging of lignocellulosic materials has been studied with a new technique involving selectively α-, β-, and γ-13C-enriched cell wall-dehydrogenation polymers (CW-DHPs) and solid state 13C NMR spectroscopy. The results from cross-polarization magic angle spinning (CP/MAS) 13C NMR experiments of unirradiated and irradiated CW-DHP have revealed mainly a decrease in the amount of end-groups of both coniferaldehyde and coniferyl alcohol type. The results suggest that these end-groups become saturated and that the terminal functionalites, i.e., γ-aldehyde and γ-hydroxymethyl groups, at least to some extent, are retained. The results indicate further that no detectable cleavage of the β-O-4 bonds occurs in the examined lignocellulosic model. In terms of proposed mechanisms of yellowing, there is marginal evidence that up to 2% of the α-labeled sites are converted by irradiation to α-carbonyls (aldehyde or ketones); moreover, we cannot dismiss the possibility that the precursor structures gi...
TL;DR: In this paper, a study on the formation of aliphatic carboxylic acids, i.e., formic and acetic acids and various hydroxy precursors, during soda-AQ, kraft, and kraft-aQ pulping of muli bamboo (Melocanna baccifera) was carried out.
Abstract: A study on the formation of aliphatic carboxylic acids, i.e., formic and acetic acids and various hydroxy monocarboxylic and dicarboxylic acids, during soda-AQ, kraft, and kraft-AQ pulping of muli bamboo (Melocanna baccifera) was carried out. Detailed gas chromatographic analyses revealed that the most abundant hydroxy carboxylic acids were 2-hydroxybutanoic, lactic, glucoisosaccharinic, glycolic, xyloisosaccharinic, 3,4-dideoxypentonic, and 3-deoxypentonic acids. The presence of AQ depressed the formation of 2-hydroxybutanoic, xyloisosaccharinic, and glucoisosaccharinic acids, and accelerated the formation of glycolic and 3-deoxypentonic acids as well as 3-deoxytetronic acid but had only a small effect on that of lactic and 3,4-dideoxypentonic acids. The total amount of aliphatic carboxylic acids corresponded to 12–15% of o.d. bamboo.