Showing papers in "Journal of Wood Chemistry and Technology in 2007"
TL;DR: In this article, the authors examined the application of select ionic liquids (ILs) as aprotic green solvents for lignin and found that up to 20 wt% Lignin can be dissolved in [hmim][CF3SO3], [mmim][MeSO4] and [bmim][meSO4].
Abstract: This study examined the application of select ionic liquids (ILs) as aprotic green solvents for lignin. Dissolution experiments were carried out employing lignin isolated from pine kraft pulp. Up to 20 wt% lignin could be dissolved in [hmim][CF3SO3], [mmim][MeSO4] and [bmim][MeSO4]. For the [bmim]+‐containing ionic liquids, the order of lignin solubility for varying anions was: [MeSO4]−>Cl−∼Br−⋙[PF6]−, indicating that the solubility of lignin was principally influenced by the nature of the anions. Ionic liquids containing large, non‐coordinating anions [PF4]− and [PF6]− were unsuitable as a solvent for lignin. 13C nuclear magnetic resonance (NMR) analyses of lignin and model compounds showed that 13C signals using ionic liquid as a solvent were shifted up‐field by δ 0.1 to 1.9 ppm in comparison to 13C NMR data acquired using dimethyl sulfoxide (DMSO) as the solvent.
546 citations
TL;DR: In this article, condensation reactions of some lignin related compounds were studied under pyrolysis conditions (air/250°C/2 ǫ) with small amount of radical coupling products derived from phenoxy and benzyl radicals.
Abstract: Condensation reactions of some lignin related compounds were studied under the pyrolysis conditions (air/250°C/2 h). Guaiacol, methylguaiacol and methylveratrole were recovered almost quantitatively with small amount of radical coupling products derived from phenoxy and benzyl radicals. Side‐chains (Cα˭Cβ, Cα‐OH) increased the condensation reactivity substantially. From the dimer structures, vinyl condensation and quinone methide mechanisms were indicated as important condensation pathways for these compounds. As for model compounds for the structures formed in lignin primary pyrolysis, coniferyl alcohol (from β‐ether structure) was very reactive, while 4,4′‐dihydroxy‐3,3′‐dimethoxystilbene (from β‐aryl structure) was stable.
84 citations
TL;DR: The surface porosities of carbon fibers derived from the polymer blend fibers of hardwood kraft lignin, HKL and polypropylene, PP, were discussed using thermal analyses, FTIR, and nitrogen adsorption as discussed by the authors.
Abstract: The surface porosities of carbon fibers derived from the polymer blend fibers of hardwood kraft lignin, HKL and polypropylene, PP, were discussed using thermal analyses, FTIR, and nitrogen adsorption. HKL/PP carbon fibers were prepared by two‐step thermal processing, thermostabilization, and carbonization. During the thermostabilization process, pores are created by oxidative degradation of the PP component. After thermostabilization some crystalline and highly oxidized PP components remained in the blend fiber. These residual PP components were subsequently pyrolyzed during carbonization, and effectively created a porous structure in the resulting carbon fibers. N2 adsorption tests of the porous carbon fibers revealed the same type of adsorption/desorption isotherms as for activated carbon fiber. The internal surface area of the HKL/PP = 62.5/37.5 carbon fibers was calculated to be 499 m2 g−1. This value was lower than that for commercial activated carbon, 745 m2 g−1. However, these porous ligni...
48 citations
TL;DR: In this article, the role of side-chain hydroxyl groups in pyrolytic reaction of phenolic β-ether type of lignin dimer was studied with several regiospecifically methylated dimers under the pyrolys conditions (N2/400°C/1.min).
Abstract: Role of side‐chain hydroxyl groups in pyrolytic reaction of phenolic β‐ether type of lignin dimer was studied with several regiospecifically methylated dimers under the pyrolysis conditions (N2/400°C/1 min). Methylation of both Cα‐ and Cγ‐hydroxyl groups reduced the Cβ‐O cleavage reactivity up to the level of the non‐phenolic type. To maintain the high reactivity of guaicylglycerol‐β‐guaiacyl ether, at least one hydroxyl group was required in the side‐chain. These results indicate that one hydroxyl group at Cα‐ or Cγ‐position acts as a hydrogen donor during pyrolysis. Influence on the product formation also indicated that the hydrogen bond types affect the reaction sequences between the Cγ‐elimination followed by the Cβ‐O cleavage and the Cβ‐O cleavage via quinone methide intermediate.
48 citations
TL;DR: In this article, the structural characteristics of lignin isolated at different ages of Nalita wood (Trema orientalis) by acidolytic dioxane method were examined by UV, FTIR, 1H•NMR and 13C−NMR spectroscopy, alkaline nitrobenzene oxidation, molecular weight determination, elemental and methoxyl analysis.
Abstract: Nalita (Trema orientalis) is one of the fastest growing trees in the tropical countries. The structural characteristics of lignin isolated at different ages of Nalita wood (Trema orientalis) by acidolytic dioxane method were examined by UV, FTIR, 1H‐NMR and 13C‐NMR spectroscopy, alkaline nitrobenzene oxidation, molecular weight determination, elemental and methoxyl analysis. The data were compared with aspen lignin. The structural analysis revealed that Nalita wood lignin is syringyl‐guaiacyl type. The methoxyl content in Nalita wood lignin was lower than aspen lignin. The C9 formulas for 30‐months‐old Nalita was C9H9.31O3.13(OCH3)1.27, whereas that of aspen was C9H8.94O3.15(OCH3)1.47. The weight average molecular weight of Nalita wood lignin was decreased from 36,500 to 25,500 with increasing tree age from 12 to 30 months, whereas weight average molecular weight of aspen was 20,000. Both alcoholic and phenolic hydroxyl group in Nalita wood lignin is lower than aspen lignin.
45 citations
TL;DR: The natural variation in wood and pulp fiber quality of 15 aspen (Populus tremuloides Michx) clones, represented by 47 trees, was assessed from 4 different sites in British Columbia, Canada as discussed by the authors.
Abstract: The natural variation in wood and pulp fiber quality of 15 aspen (Populus tremuloides Michx) clones, represented by 47 trees, was assessed from 4 different sites in British Columbia, Canada. Kraft pulping trials revealed substantial variation in the pulping efficiencies, illustrated by differences of 6% in total pulp yield, ∼30% differences in H‐factor required to attain a target kappa of 21, and differences of up to 2 ISO brightness units in bleachability of kappa 21 pulp. Clearly, enormous variation exists in the natural stands of aspen, and presents some exciting opportunities for selecting clonal aspen for targeted end‐product applications. A comprehensive characterization of wood chemical composition, wood density, and fiber properties indicated that pulp yield is directly related to syringyl lignin monomer composition, and not inherent wood density, regardless of geographic locations, whereas pulp bleachability and viscosity appear to be associated with the inherent cell wall thickness of t...
37 citations
TL;DR: In this paper, lignins isolated from pine milled wood and residual enzyme lignin (REL) were compared using modified thioacidolysis, modified DFRC, gel permeation chromatography (GPC), two-dimensional Heteronuclear Multiple Quantum Coherence (HMQC) NMR, and quantitative 13C NMR.
Abstract: Lignins isolated from pine milled wood, milled wood lignin (MWL), and residual enzyme lignin (REL) were compared using modified thioacidolysis, modified DFRC, gel permeation chromatography (GPC), two‐dimensional Heteronuclear Multiple Quantum Coherence (HMQC) NMR, and quantitative 13C NMR. Dissolution of the lignin for solution‐state NMR was accomplished by utilizing the recently reported DMSO/N‐methylimidazole/acetic anhydride solvent system. Contrary to previous reports, comparison of the lignin preparations by thioacidolysis indicated that REL was more structurally similar to the lignin in the milled wood and Wiley wood meal than MWL. Total monomer yields indicated that the MWL was lower in β‐aryl ether content than the other preparations, and this was verified by quantitative 13C NMR. NMR analysis indicated that the inter‐unit linkages present in all the lignin preparations are consistent with the present knowledge about lignin biosynthesis. The contribution of minor end group structures in t...
36 citations
TL;DR: In this article, the chemical structural changes of Lodgepole pine milled wood lignin (MWL) before and after polyoxometalate (POM) oxidation were investigated using gel permeation chromatography (GPC), Fourier Transform infrared spectroscopy (FTIR), and solution-state nuclear magnetic resonance (NMR) data.
Abstract: The chemical structural changes of Lodgepole pine milled wood lignin (MWL) before and after polyoxometalate (POM) oxidation were investigated using gel permeation chromatography (GPC), Fourier Transform infrared spectroscopy (FTIR), and solution‐state nuclear magnetic resonance spectroscopy (NMR). 13C NMR spectroscopic data revealed an approximately 28% decrease in α‐OH/β‐O‐4 inter‐unit linkages after POM treatment. This was accompanied by an increase in carbonyl and phenolic hydroxyl content. These results suggest POM oxidation involved side chain (such as α‐OH/β‐O‐4) oxidation and/or degradation of some of the inter‐unit linkages. Quantitative 13C NMR along with GPC analysis revealed an increase in the degree of condensation of the MWL as a result of POM treatment, suggesting radical coupling as a major reaction pathway.
32 citations
TL;DR: In this article, process parameters that may affect the retention of OBA were investigated, such as furnish composition, OBA charge, contacting time, water hardness, anionic trash, and fines in HYP.
Abstract: Optical brightening agents (OBA) or fluorescent whitening agents (FWA) are commonly used in the paper industry to improve the optical performance of paper products. The increased use of bleached chemi‐thermo‐mechanical pulp (BCTMP) or high‐yield pulp (HYP) in printing and writing paper grades has initiated research topics on the brightening efficiency of OBA on mechanical pulp‐containing furnishes. In this study, process parameters that may affect the retention of OBA were investigated, such as furnish composition, OBA charge, contacting time, water hardness, anionic trash, and fines in HYP. It was found that OBA had lower retention on HYP fibers than on bleached kraft pulp (BKP) fibers. Efforts were also made to understand the underlying mechanism.
27 citations
TL;DR: The structure of copper and zinc tebuconazole acetate and zinc cis-propiconazole chloride were examined by X-ray crystallography in this article, where the copper atom lies on a crystallographic inversion center and is coordinated to two triazole and two acetate ligands in a trans arrangement.
Abstract: Divalent copper and zinc complexes with metal:azole ratio 1∶2 were readily formed at room temperature with the fungicides tebuconazole and propiconazole. The structure of copper and zinc tebuconazole acetate and zinc cis‐propiconazole chloride were examined by X‐ray crystallography. In copper tebuconazole acetate, the copper atom lies on a crystallographic inversion center and is coordinated to two triazole and two acetate ligands in a trans arrangement. The two binding tebuconazole N atoms and two close binding acetate O atoms form a square plane. The two remaining acetate O atoms have more distant interactions, thus forming an elongated octahedron around the copper atom. The coordination geometry of zinc tebuconazole acetate is tetrahedral and the metal is bound to two triazole and two acetate ligands. The geometry is distorted from regular owing to the size of the tebuconazole ligands. The butyl chains are less folded than for the copper tebuconazole complex, resulting in a more extended molec...
26 citations
TL;DR: In this article, acid precipitation of lignin in the presence of magnetite followed by an applied magnetic field provides a simple method for enhanced Lignin recovery from an aqueous stream.
Abstract: This study demonstrates that acid precipitation of lignin in the presence of magnetite followed by an applied magnetic field provides a simple method for enhanced lignin recovery from an aqueous stream. The extraction procedure was shown to be sensitive to the relative charge of magnetite and solution pH. Under optimized conditions, 93 wt.% of the softwood lignin from a kraft cooking liquor could be recovered employing this novel separation approach.
TL;DR: In this paper, the morphological, chemical, and papermaking properties of compression wood are distinctively different from those of normal juvenile wood and mature wood and this enables accurate quantitative genetic analyses of these properties for tree breeding programs.
Abstract: All loblolly pine trees, especially the juvenile portion, contain various amounts of compression wood. The morphological, chemical, and papermaking properties of compression wood are distinctively different from those of normal juvenile wood and mature wood. Compression wood has higher lignin and galactan, but lower cellulose and mannan content, shorter average fiber length, lower fiber width but thicker cell wall, higher fiber coarseness and higher microfibril angles as compared with the corresponding normal wood. Micro analytical methods have been developed to quantitatively determine the percentage of compression wood in an incremental core so as to eliminate the effects of compression wood on the aforementioned properties. This enables accurate quantitative genetic analyses of these properties for tree breeding programs.
TL;DR: In this article, the authors determined the pulping yields for steam-exploded and untreated mixed hardwood chips for kraft pulping processes with and without anthraquinone and/or polysulphide.
Abstract: We determined the pulping yields for steam‐exploded and untreated mixed hardwood chips for kraft pulping processes with and without anthraquinone and/or polysulphide. The pulp yield from steam‐exploded chips was 1–3% lower than from untreated chips under similar conditions. The benefit of kraft pulping with anthraquinone and/or polysulphide was found to be more pronounced for the exploded chips than for the untreated chips.
TL;DR: In this paper, different pretreatment methods, including microwave irradiation, organosolv process catalyzed by acid or alkali, were compared with rice hulls via pretreatment served as a solid substrate for cellulase production.
Abstract: Rice hulls via pretreatment served as a solid substrate for cellulase production. Different pretreatment methods, including microwave irradiation, organosolv process catalyzed by acid or alkali were compared. With rice hulls pretreated by microwave irradiation coupled with alkaline pretreatment and rice hulls pretreated with organosolv process catalyzed with acid or alkali, the maxima of filter paper activity (FPA) obtained during the fermentation were 18%, 21%, 31% higher, and maxima of the carboxy‐methyl cellulase (CMCase) were 7.7%, 14%, 16% higher than those obtained with the rice hulls pretreated only with alkali, respectively. The ratios of cellulose degradation were also estimated and they showed similar tendency with the maxima of FPA detected in the fermentation processes.
TL;DR: In this article, surface plasmon resonance analysis was performed on hemicelluloses, xylan and glucomannan, with monolignols, coniferyl alcohol and sinapyl alcohol, and their glucosides, coniferin and syringin.
Abstract: Interactions of hemicelluloses, xylan and glucomannan, with monolignols, coniferyl alcohol and sinapyl alcohol, and their glucosides, coniferin and syringin, were investigated by surface plasmon resonance analysis. Hemicelluloses with different aldehyde contents, prepared by sodium periodate oxidation, were immobilized onto carboxymethyl–dextran–coated gold plates by reductive amination. The interaction of the hemicelluloses with monolignols was evaluated as weight gain of the hemicelluloses at neutral pH. Both hemicelluloses adsorbed the monolignols in much larger amounts than the corresponding glucosides. The adsorption tendency was independent of aldehyde content. These results suggest the hemicelluloses have higher affinities to the aglycons than the glucosides. Thus, the interactions of the hemicelluloses with monolignols are primarily the result of hydrophobic interactions. However, binding constants were not estimated because of the low solubility of the monolignols in the aqueous buffered...
TL;DR: In this article, the light absorption coefficient, light scattering coeffient, and brightness of unbleached softwood kraft pulp were compared in the TCF and ECF bleaching sequences.
Abstract: Unbleached softwood kraft pulp was fractionated in hydrocyclones into a fine fraction, enriched in earlywood fibers, and a coarse fraction, enriched in latewood fibers. The response to individual bleaching chemicals and the bleachability in bleaching sequences of the pulp fractions was studied. The light absorption coefficient, light scattering coeffient, and brightness were higher in the unbleached fine fraction than in the coarse fraction. Hydrogen peroxide managed to reduce the light absorption coefficient of the earlywood enriched fine fraction more efficiently than that of the latewood enriched fraction. In the TCF-sequence the light absorption coefficient of the fine fraction was reduced to the level of the coarse fraction at a given consumption of bleaching chemicals. In the ECF-sequence the difference in light absorption coefficient remained between the fractions. At a given consumption of bleaching chemicals, the fine fraction had higher brightness than the coarse fraction, 2%- and 1%-units on the ISO-scale in the TCF and ECF bleaching sequence, respectively.
TL;DR: In this article, a modified stannous chloride stain capable of specifically identifying arsenic in preservative-treated wood was developed by causing the over-reduction of molybdenum with stANNous chloride prior to sample addition, which reduced the stain sensitivity to the background phosphate levels in the wood and permitted the detection of elevated arsenate concentrations.
Abstract: Convenient and rapid detection of arsenic in treated wood products is necessary when evaluating possible exposure risks from the product during in‐service use and disposal. For this study, a modified stannous chloride stain capable of specifically identifying arsenic in preservative‐treated wood was developed by causing the over‐reduction of molybdenum with stannous chloride prior to sample addition. This reduced the stain's sensitivity to the background phosphate levels in the wood and permitted the detection of elevated arsenate concentrations. The modified stain was confirmed through field testing with weathered wood samples. Alternative application techniques, such as wipes, were further explored.
TL;DR: Douglas fir heartwood thermomechanical pulp was treated with laccase enzymes at 25 and 50°C with and without added oxygen as discussed by the authors, and the treated pulps were bleached with hydrogen peroxide at increasing alkali charges.
Abstract: Douglas‐fir heartwood thermomechanical pulp was treated with laccase enzymes at 25 and 50°C with and without added oxygen The treated pulps were bleached with hydrogen peroxide at increasing alkali charges Laccase treatments without added oxygen increased bleached brightness by 15–25 pts ISO, and decreased hydrogen peroxide consumption by 15–20% The enzyme treatments were not enhanced when supplemented with oxygen When the effectiveness of four different laccase enzymes was compared for the treatment of Douglas‐fir heartwood thermomechanical pulp, there were no significant differences found in the performance among the enzymes Possible explanations for the observed results are given
TL;DR: In this article, low-field proton NMR was evaluated as a nondestructive and rapid technique for measuring ethanol-soluble extractives in southern pine wood, which was steeped in extractivecontaining solutions to generate extractive-enriched samples for analysis.
Abstract: Low‐field proton NMR was evaluated as a nondestructive and rapid technique for measuring ethanol‐soluble extractives in southern pine wood. Matchstick‐sized wood specimens were steeped in extractive‐containing solutions to generate extractive‐enriched samples for analysis. Decay curves obtained by the Carr‐Purcell‐Meiboom‐Gill (CPMG) pulse sequence were analyzed with Contin, a constrained regularization program used to generate continuous distributions of transverse (spin‐spin) relaxation times. Air‐dry wood samples gave maximum signal amplitudes that did not clearly reflect differences in extractives content. Oven drying removed signals for bound water that were superposed with those for the extractives. Relaxation times and the corresponding amplitudes were then positively correlated with the added extractives. Treatment of air‐dry samples with dichloromethane‐d 2 prior to analysis increased the mobility of the extractives, thereby resulting in a shift of the corresponding signals to longer rel...
TL;DR: In this article, two reaction systems were investigated; one involving hydrogenation of the cinnamic acid ethyl ester glucoside intermediate followed by diisobutylaluminium hydride (DIBAL•H) reduction of the ester to the alcohol, and the other involving DIBAL−H reduction of CEG to coniferin followed by hydrogenation.
Abstract: Dihydroconiferyl alcohol glucoside has been synthesized from cinnamic acid ethyl ester glucoside. Two reaction systems were investigated; one involving hydrogenation of the cinnamic acid ethyl ester glucoside intermediate followed by diisobutylaluminium hydride (DIBAL‐H) reduction of the ester to the alcohol, and the other involving DIBAL‐H reduction of the cinnamic acid ethyl ester to the alcohol (coniferin) followed by hydrogenation. Hydrogenation followed by DIBAL‐H reduction led to higher dihydroconiferyl alcohol glucoside yields and avoided by‐product formation associated with the hydrogenation of coniferin.