Search

The objective of this study was to evaluate the possibility of producing dissolving grade pulp from tobacco stalk through combining SO2-ethanolwater (SEW) fractionation, alkaline extraction, and bleaching with oxygen (O), chlorine dioxide (D), alkaline extraction with hydrogen peroxide (Ep), and hydrogen peroxide (P) (OD0(Ep)D1P). The results showed that the optimum SEW cooking condition to remove the original xylan and lignin in tobacco stalk to an acceptable level was 6% SO2 charge (by weight) at 135 °C for 180 min. A bleachable pulp (Kappa number of 21.5) was produced from the SEW-treated tobacco stalk via a subsequent 1% NaOH extraction. After the OD0(Ep)D1P sequence bleaching, the bleached pulp showed a high brightness (88.1% ISO) and a high α-cellulose content (94.9%). The viscosity (15.8 cP) and the residual xylan content (4.4%) of the pulp were within acceptable levels for dissolving pulp production. Thus, tobacco stalk was shown to be a viable raw material for dissolving pulp production following a SEW treatment, alkaline extraction, and a conventional bleaching sequence. [ABSTRACT FROM AUTHOR]

Hemicellulose is an abundant and underutilized carbohydrate polymer in plants. The objective of this study was to understand the effect of delignification on hemicellulose extraction efficiency with different types of lignocellulosic biomass. In the case of pine, with a prior sodium chlorite or peracetic acid delignification, more than 50% of the original hemicellulose in the biomass could be extracted using a 10% sodium hydroxide solution; without delignification, only 3.4% of hemicellulose could be extracted from pine. In contrast, without prior delignification, acceptable hemicellulose extraction efficiencies (55.5% and 50.7%, respectively) were achieved from switchgrass and poplar. In addition, the effect of hemicellulose extraction processes on the enzymatic convertibility of the celluloserich residues after extraction was determined. The cellulose-rich residues from switchgrass after hemicellulose alkali extraction showed high glucose recovery with enzyme hydrolysis with or without prior delignification. For pine and poplar, high glucose recovery with enzyme hydrolysis of the cellulose-rich residues only occurred if the sample had a delignification step prior to hemicellulose extraction. This information on commercially available biomass feedstocks is useful for those considering isolating hemicellulose within a biorefinery concept. [ABSTRACT FROM AUTHOR]

Lignin is an amorphous polymer that limits the enzymatic conversion of polysaccharides to fermentable sugars. Thus, a pretreatment that can enhance the accessibility of carbohydrates is a key step of successful biofuel conversion schemes. In this study, corn stover was fractioned into stem, cob, and leaf because their lignin is different. To elucidate the lignin changes, autohydrolysis, diluted acid, and alkali pretreatments were applied on the samples, followed by the isolation of cellulolytic enzyme lignin preparations. Alkaline nitrobenzene oxidation, 13C-Nuclear Magnetic Resonance (NMR), and 1H-13C heteronuclear single quantum coherence NMR were used to profile the lignin changes. The results indicated that corn stover lignin is a p-hydroxyphenyl-guaiacyl-syringyltype lignin that incorporates p-coumarate and ferulate esters. The β-arylether was the most abundant inter-unit linkage, followed by condensed linkages, e.g. pino-/syringaresinol, phenylcoumaran, and spirodienone. As for the non-pretreated samples, leaf lignin was more condensed than stem lignin and cob lignin. More lignin was removed by the alkali pretreatment due to more cleavage of β-aryl-ether linkages. As a comparison, more condensed linkages were generated by the acidic pretreatments. The decrease of the syringyl/guaiacyl ratio indicated that the residual lignin became more condensed and confirmed that guaiacyl and p-hydroxyphenyl units were more stable than syringyl units during the pretreatment. [ABSTRACT FROM AUTHOR]

A two-step hydrolysis method was evaluated as a potential means of obtaining high yields of furfural and levulinic acid from corn stover using sulfuric acid as catalyst in a water/gamma-valerolactone (GVL) system. The corn stover underwent a high-temperature hydrolysis process to produce levulinic acid, followed by a low-temperature hydrolysis process to produce furfural. A series of experiments were conducted to explore the relationship between the different reaction parameters and the final yields of furfural and levulinic acid. Scanning electron microscopy (SEM) pictures together with X-ray diffraction (XRD) analysis were used to further elaborate on the hydrolysis results. Molar yields of about 70.65% furfural and 57.7% levulinic acid were obtained by applying this method with a low temperature of 140 °C and a high temperature of 190 °C, together with 0.2 M of sulfuric acid used as the catalyst. These results indicated that this was an effective way to obtain satisfactory yields of furfural and levulinic acid from corn stover. [ABSTRACT FROM AUTHOR]

Selective conversion of biomass-derived carbohydrates into 5-hydroxymethylfurfural (HMF) is of great significance for biomass conversion. In this study, a novel solid Brønsted acid was prepared simply by the copolymerization of paraformaldehyde and p-toluenesulfonic acid and then used to catalyze the conversion of various carbohydrates into HMF in γ-valerolactone-water (GVL/H2O) reaction medium for the first time. The catalyst exhibited strong acidity, good water resistance, and high thermal stability. The present work focuses on the effects of various reaction parameters, including reaction temperature, time, water concentration, solvent, fructose level, and catalyst loading, on fructose dehydration. The catalyst exhibited excellent catalytic performance for HMF production from fructose in GVL and furnished a high HMF yield of 78.1% at 130 °C in 30 min. The recycling experiments suggested that the solid acid catalyst could be recycled at least seven times without a noticeable decrease in the catalytic activity. In addition, an attempt to study the one-step conversion of sucrose, glucose, and cellulose into HMF and furfural was performed using the same catalytic system. [ABSTRACT FROM AUTHOR]

Cadium sulfide/titanium dioxide (CdS/TiO2) catalyst was prepared by two different methods: microemulsion-mediated solvothermal hydrolyzation (CdS/TiO2 (SH)) and in-situ sulfurization under supercritical conditions (CdS/TiO2 (SS)). The photocatalysts were characterized by nitrogen adsorption-desorption, X-ray diffraction, X-ray photoelectron spectra, UVVis absorption spectra, and PL spectra. Photodegradation reactions of three monomeric and one dimeric lignin model compounds, and kraft pine lignin (Indulin AT) were carried out at room temperature in a weak alkaline aqueous system by visible light irradiation with air bubbling. Quantitative results showed that these lignin model compounds and kraft lignin were effectively degraded. While both phenolic and non-phenolic lignin units are reactive, the phenolic units appeared to react faster and preferentially reacted. [ABSTRACT FROM AUTHOR]

Kraft pulping is one possible pretreatment for softwood to economically produce bioethanol. This work evaluates the techno-economic potential of using the kraft process for producing bioethanol from softwoods in a repurposed or co-located kraft mill. Pretreated loblolly pine was enzymatically hydrolyzed at low enzyme dosages of 5 and 10 FPU/g of substrate. Pretreated residue with 13% lignin content had the highest sugar recovery, 32.7% and 47.7% at 5 and 10 FPU/g, respectively. The pretreated residues were oxygen delignified and refined. In all cases, oxygen delignification improved sugar recovery, while refining was mostly effective for pulps with high lignin content. At 5 FPU/g, the sugar recovery for all kraft pulps was 51 to 53% with oxygen delignification and refining. Increasing the enzyme dosage to 10 FPU/g increased the sugar recovery for these pulps to greater than 60%. Economic analysis for the pulps with different initial lignin content showed that kraft pulps with an initial lignin content of 6.7% with oxygen delignification had an ethanol yield of 285 L/ODt wood and the lowest total production cost of $0.55/L. Pulps with initial lignin content of 18.6% had a total production cost of $0.64/L with an ethanol yield of 264 L/ODt wood. [ABSTRACT FROM AUTHOR]

A novel two-step process for pretreatment of corn stover was investigated with the goal of increasing sugar recovery and decreasing the capital cost. In the process, corn stover was first treated with dilute hydrochloric acid to maximize xylan recovery, and then the residue was treated with aqueous ammonia to alter the lignin structure and swell the cellulose surface. The optimal conditions were 110 °C and 40 min for 1% dilute hydrochloric acid pretreatment with a liquid to solid ratio of 10:1 followed by aqueous ammonia pretreatment at 37% NH3, 130 °C, 30 min, and liquid to solid ratio of 6:1. Under these pretreatment conditions, the glucan and xylan recoveries were 83.2% and 97.3%, respectively, with cellulase dosage at 15 FPU/g of substrate. When the cellulase dosage was decreased from 15 FPU/g to 10 FPU/g of substrate, the glucan recovery only dropped to 70%, while the xylan recovery remained high at 95.1%. The results show that this two-step pretreatment was effective for achieving high sugar recovery from corn stover by enzymatic hydrolysis. [ABSTRACT FROM AUTHOR]

Green liquor (Na2S + Na2CO3, GL) pretreatment is an effective pathway for improving the enzymatic digestibility of lignocellulosic biomass for the production of bioethanol. In this work, GL was employed as a pretreatment to enhance the enzymatic saccharification of poplar. During pretreatment, the increase of H-factor and TTA charge resulted in enhanced delignification and increased degradation of polysaccharides. The sugar yield of enzymatic hydrolysis increased rapidly with increasing TTA charge in GL pretreatment, while the effect of different H-factors (from 400 to 800) on sugar yield was unnoticeable. The pretreated solid recovery was 75.5% at a lignin removal rate of 29.2% under optimized conditions of total titratable alkali (TTA) charge 20%, sulfidity 25%, and H-factor 400. The sugar yield of glucan, xylan, and total sugar of GLpretreated poplar in enzymatic hydrolysis reached up to 89.9%, 65.5%, and 82.8%, respectively, at a cellulase loading of 40 FPU/g-cellulose. [ABSTRACT FROM AUTHOR]

Corn stover is an abundant feedstock in the US that can be used for second generation bioethanol production. However, there is little useful data on structure of the lignin of corn stover. The following principal tasks will be addressed to profile the structure of corn stover: (1) separation of corn stover into stem, cob, and leaf; (2) isolation of cellulolytic enzyme lignins (CEL) from extractive-free and the alkali-treated fractions; (3) quantification of p-coumarate and ferulate of fractions by HPLC. The results of alkaline nitrobenzene oxidation and ¹H-13C HSQC NMR indicated: (1) the structure of lignin varied in the fractions; (2) a remarkable amount of p-coumarate and ferulate was identified and determined; (3) the remarkable structural changes of lignin induced by alkaline treatment were elucidated. [ABSTRACT FROM AUTHOR]

Hemicellulose material is an abundant and relatively under-utilized hetero-polysaccharide material present in lignocellulosic materials. In this study, an alkaline treatment was applied to sweetgum and Eucalyptus globulus chips to extract hemicelluloses prior to kraft pulping to subsequently evaluate the final product and process. An alkaline extraction (10 and 50% NaOH by weight on wood) for 60 min at 100 °C followed by precipitation in ethanol recovered 4.3% of the biomass as a predominantly xylan material (sweetgum 50% NaOH) with an average degree of polymerization around 250 and functional groups similar to a commercial xylan (sweetgum 10% NaOH). This process in comparison to autohydrolysis (water extraction at 100 °C) produced a much higher molecular weight and more pure hemicellullose. The results obtained indicate a promising combination between the effective extraction of hemicellulose from wood and a distillation process that recovers the ethanol, which may be an attractive alternative to recover liquor and ethanol after hemicellulose precipitation. Hemicellulose from sweetgum showed more thermal stability with high molecular weight compared to the hemicellulose extracted from Eucalyptus globulus. An attractive alternative looks to be to recover liquor and ethanol after hemicellulose precipitation. [ABSTRACT FROM AUTHOR]

Background: Despite decades of work and billions of dollars of investments in laboratory and pilot plant projects, commercial production of cellulosic ethanol is only now beginning to emerge. Because of: (1)high technical risk coupled with; (2) high capital investment cost relative to ethanol product value, investors have not been able to justify moving forward with large scale projects on woody biomass. Results: Both issues have been addressed by targeting pulp and paper industry processes for application in bioethanol production, in Greenfield, Repurpose and Co-Location scenarios. Processes commercially proven in hundreds of mills for many decades have been tailored to the recalcitrance of the biomass available. Economically feasible cellulosic bioethanol can be produced in Greenfield application with hardwoods, but not softwoods, using kraft mill equipment. Both types of wood species can profitably produce ethanol when kraft mill or newsprint assets are Repurposed to a biorefinery. A third situation which can generate high financial returns is where excess kraft pulp is available at a mill which has no excess drying capacity. Each scenario is supported by laboratory simulation, engineering and financial analysis. While pretreatment is critical to providing access of the biomass to enzymes, capital investment per unit of ethanol produced can be attractive, even if ethanol yield is modest. Conclusions: Three guiding principles result in attractive economics: (1) re-use existing assets to the maximum extent; (2) keep the process as simple as possible; (3) match the recalcitrance of the biomass with the severity of the pretreatment. [ABSTRACT FROM AUTHOR]

Milled wood lignin (MWL) was widely characterized to demonstrate the structure of native lignin by liquid state 13C NMR. As an isolated lignin, the structure of MWL was influenced by the isolation procedure performed. In this article, hardwood (sweetgum) and softwood (loblolly pine) were subjected to various isolation conditions to elucidate the effect of extracting temperature and milling time on the structure of MWL. Purification was also carried out on the crude MWL. The structure of the crude MWL and the purified MWL was identified and quantified by 13C NMR. Based on the yield and the lignin content of the crude MWL, the optimal isolation was achieved with 8 h milling and 20 °C extracting for hardwood. For softwood, the optimal isolation condition for crude MWL was 12 h milling and 20 °C extracting. [ABSTRACT FROM AUTHOR]

The cleavage of lignin bonds in a wood matrix is an important step in the processes employed in both the biorefinery and pulp and paper industries. β-O-4 ether linkages are susceptible to both acidic and alkaline hydrolysis. The cleavage of α-ether linkages rapidly occurs under mildly acidic reaction conditions, resulting in lower molecular weight lignin fragments. Acidic reactions are typically employed in the biorefinery industries, while alkaline reactions are more typically employed in the pulp and paper industries, especially in the kraft pulping process. By better understanding lignin reactions and reaction conditions, it may be possible to improve silvicultural and breeding programs to enhance the formation of easily removable lignin, as opposed to more chemically resistant lignin structures. In hardwood species, the S/G ratio has been successfully correlated to the amount of β-O-4 ether linkages present in the lignin and the ease of pulping reactions. [ABSTRACT FROM AUTHOR]

A simple and rapid dual-wavelength spectroscopic method is used for simultaneous determination of pentoses and hexoses in the prehydrolyzate from lignocellulosic biomass. The method is based on the following reaction mechanism: in the solution of hydrochloric acid, phloroglucinol gives color reaction with sugars or their degradation products, showing maximum absorbance at 553 nm and 410 nm. Based on dual-wavelength spectrophotometric measurement, the pentoses and hexoses can separately be quantified. It was found that the derivatives from these two different sugars have an isosbestic point at 425 nm. According to the validation results, high accuracy and reasonable recovery rate is shown with the present method (pentoses recovery 97.1 to 100.0%, hexoses recovery 97.2 to 102.0%). Additionally, the interferences from substances including lignin, furfural, 5-hydroxymethyl furfural (HMF), glucuronic acid, and galacturonic acid are insignificant. All of the above results illustrate the suitability of this method for analyzing sugars in the lignocelluloses prehydrolyzate, especially hardwoods or herbaceous plants, based on forest-related biorefinery research. [ABSTRACT FROM AUTHOR]

Red maple, sweet gum, trembling aspen, red alder, and Eucalyptus globulus samples were pretreated with dilute sulfuric acid and green liquor before enzymatic saccharification. Substrates showed different levels of delignification and sugar recovery, depending on the applied pretreatments and the syringaldehyde/vanillin ratio (S/V). Three major conclusions were drawn in this research. First, lignin is the greatest contributor to recalcitrance of hardwood to enzymatic saccharification. Second, a high S/V ratio is a useful indicator of high delignification during a pretreatment process. Third, green liquor pretreatment is a promising pretreatment method because of a high delignification degree and sugar recovery. In addition, xylan also contributes to the recalcitrance of hardwoods toward enzymatic saccharification. [ABSTRACT FROM AUTHOR]

In an attempt to explain variations in delignification behaviors among different hardwood species, the kraft pulping delignification rates of Eucalyptus urograndis, E. nitens, E. globulus, sweet gum, maple, red oak, birch, red alder, cottonwood, and acacia were obtained and correlated with their respective lignin chemical structures. Since H-factor for hardwood is calculated based on the softwood activation energy (Ea) value, a comparison between softwood vs. hardwood activation energy was also performed. Lignin was isolated by a modified isolation protocol, using alkaline pretreatment of the wood prior to isolation. The lignin preparations were analyzed via quantitative 13C NMR spectroscopy. Substantial variations were found among the hardwood species studied. A linear correlation between the kraft delignification rate and the amount of syringyl units was found. Activation energy values obtained for kraft pulping of hardwoods were very similar and almost identical to the value obtained for softwood. Birch was the only species with outlier behavior. [ABSTRACT FROM AUTHOR]

quantitative approach to characterize lignin-carbohydrate complex (LCC) linkages using a combination of quantitative C NMR and HSQC 2D NMR techniques has been developed. Crude milled wood lignin (MWLc), LCC extracted from MWLc with acetic acid (LCC-AcOH) and cellulolytic enzyme lignin (CEL) preparations were isolated from loblolly pine ( Pinus taeda) and white birch ( Betula pendula) woods and characterized using this methodology on a routine 300 MHz NMR spectrometer and on a 950 MHz spectrometer equipped with a cryogenic probe. Structural variations in the pine and birch LCC preparations of different types (MWL, CEL and LCC-AcOH) were elucidated. The use of the high field NMR spectrometer equipped with the cryogenic probe resulted in a remarkable improvement in the resolution of the LCC signals and, therefore, is of primary importance for an accurate quantification of LCC linkages. The preparations investigated showed the presence of different amounts of benzyl ether, γ-ester and phenyl glycoside LCC bonds. Benzyl ester moieties were not detected. Pine LCC-AcOH and birch MWLc preparations were preferable for the analysis of phenyl glycoside and ester LCC linkages in pine and birch, correspondingly, whereas CEL preparations were the best to study benzyl ether LCC structures. The data obtained indicate that pinewood contains higher amounts of benzyl ether LCC linkages, but lower amounts of phenyl glycoside and γ-ester LCC moieties as compared to birch wood. [ABSTRACT FROM AUTHOR]

Softwood species generally have been found very recalcitrant to enzymatic hydrolysis of the carbohydrate fractions to monomeric sugars. To solve this problem, loblolly pine chips were pretreated with green liquor at 12-20% Total Titratable Alkali (TTA) (as Na2O on wood) at 170°C for 800 H-factor. The yield of resulting pulp was 76.5-78.6% and the lignin content decreased from 29.2 to 20.2-22.4% and the total polysaccharide decreased from 62.6 to 53.8-55.0%, all based on the weight of original wood. When the pulp was subjected to enzymatic hydrolysis using 40 Filter Paper Unit (FPU)/g pulp, only 41% of the polysaccharides in wood were converted to monomeric sugars. This conversion figure is much lower than that of mixed southern hardwoods (80%) treated under similar conditions. If the green liquor treated pulp was further subjected to either oxygen delignification or mechanical refining prior to the enzymatic hydrolysis, the conversion rate increased to around 55% and 60%, respectively. Furthermore, combination of oxygen delignification and refining further increased the total sugar conversion to 78% of the total sugar in wood, approximately equal to that of the mixed southern hardwoods. [ABSTRACT FROM AUTHOR]

The development of a new, relatively simple process, which uses green liquor (sodium carbonate and sodium sulfide) as a pretreatment for the production of ethanol is described in this article. The pulps produced by this process can be enzymatically hydrolyzed to monomeric sugars with a high overall sugar recovery. The use of green liquor for pretreatment ensures that the chemicals used during pretreatment can be recovered efficiently using proven technology and can be easily implemented in a repurposed kraft pulp mill. The yield of pulps produced by the green liquor pretreatment process is about 80% with nearly 100% cellulose and 75% xylan in retention in mixed southern hardwood. The low pH prevents the random hydrolysis of polysaccharide and secondary peeling reactions from occurring during the pretreatment, resulting in higher retention of the polysaccharides in pulp. About 35% of the lignin is removed during the green liquor pretreatment process, which is sufficient for efficient enzymatic hydrolysis. The amount of sugar produced in enzymatic hydrolysis increased with both the green liquor and enzyme charge. The increase in enzymatic hydrolysis efficiency was small as the total titrateable alkali was increased beyond 12-16%. With green liquor pretreatment at 16% Total Titrateable Alkali (TTA), the overall sugar recovery for hardwood was shown to be around 77% at a cellulase charge of 20 FPU/gm of substrate. A sugar recovery of 80% could be achieved at higher enzyme charges. These levels of sugar recovery are competitive with other pretreatments for hardwood. This novel pretreatment process can be used to repurpose kraft mills, which are being closed due to a decrease in the demand for paper in North America, for production of ethanol. [ABSTRACT FROM AUTHOR]

A rapid method for simultaneous determination of furfural and hydroxymethylfurfural (HMF) in the filtrate of an acidic treatment of biomass was developed based on UV spectrophotometer. Interference from acid soluble lignin is alleviated by the use of absorbance difference spectrum before and after reduction with sodium borohydride (NaBH4). The concentrations of furfural and HMF in the filtrate are determined by measuring the absorbance of the difference spectrum at 277 nm and 285 nm, the characteristic absorption maxima for furfural and HMF, respectively. Two simultaneous equations are solved to obtain the concentrations of furfural and HMF in the filtrate. Acid soluble lignin in the solution is determined to cause negligible interference on the analysis. [ABSTRACT FROM AUTHOR]

The kinetics of the oxidation of a series of substituted phenols by polyoxometalate (POM), K5[SiVW11O40] · 12H2O were investigated. Under all conditions studied second-order kinetics were observed. Electron-transfer from neutral phenols (k1) was slower than that from the corresponding phenoxide anions (k2), and the reaction rate was highly dependent on the nature of the substituent groups. The observed rate constants decreased in the order: p-methoxyphenol (1)>p-methylphenol (2)>m-methylphenol (4)>m-methoxyphenol (3)>phenol (5)>p-chlorophenol (6)>p-bromophenol (7)>m-chlorophenol (8)>m-nitrophenol (9). A Hammett plot of the data revealed a better correlation with σ+ than with σ, suggesting a reaction involving the formation of an electron-deficient radical intermediate with the rate-determining step being an electron-transfer from a neutral substrate. Depending on the concentration of POM, oxidized phenolic and oxidative coupling products were detected. [ABSTRACT FROM AUTHOR]

AbstractVarious lignin model compounds were oxidized with polyoxometalate (POM), K5[SiVW11O40]·12 H2O, in sodium acetate buffer (I=0.2 M, pH 5.0) and the reaction kinetics were investigated. The reactions were found to have second order reaction rates, first order with regards to both lignin model compound and POM. A dramatic increase in reactivity was observed upon addition of methoxyl groups in ortho-positions to the phenolic hydroxyl group. Syringyl units reacted faster than guaiacyl units. Reaction rates of para-substituted guaiacyl and syringyl model compounds showed a strong dependency on the nature of the substituents. The reaction rate of a 5-5′ dimer lignin model compound was extremely fast. The addition of the ortho-phenol substituent not only increased the electron density of the aromatic ring, but also helped stabilize the intermediate phenoxy radical through resonance stabilization and delocalization. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 the MWL are further decreased in the milled wood, indicating that they are preferentially isolated as low molecular weight material, possibly generated during the milling process. All other structural moieties were similar in all preparations. GPC data indicated that the milled wood and REL both contain a portion of lignin with a molecular weight of 55,000 g/mol. Data indicate that the inefficiency of the DFRC method may be related to molecular mobility or accessibility in higher molecular weight portions of the lignin polymer. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Cellulolytic enzyme lignin (CEL) and milled wood lignin (MWL) were prepared by three different ball-milling methods. The structure of CEL at various yields was elucidated and compared with MWL using wet chemical analysis, FTIR and solution-state NMR techniques. Results show that ball milling of wood degrades β-O-4 structures in lignin. However, even after extensive ball milling, less than 25% of the β-O-4 structures were degraded. The extent of degradation was less for softwood than for hardwood lignin. Extractable lignin yield, either MWL or CEL, was the best way to assess the extent and effect of ball milling. CEL is preferred over MWL, as it can be isolated in higher yield with less degradation. CEL was isolated at yields ranging from 20% to 86%. Over this range the CEL had similar structures, suggesting that lignin in the secondary wall is uniform in structure. The residual enzyme lignin (REL) was structurally different from CEL and may originate mainly from the middle lamella. In this paper we propose a new procedure for the isolation of lignin for use in structural studies, whereby wood is sufficiently milled and successively extracted to produce three lignin fractions representing the total lignin in wood. [ABSTRACT FROM AUTHOR]

Our objective was to study the extractives content and the bleachability of batch extended delignified kraft pulps during the black liquor recycling. Extractives accumulated in the black liquor during the black liquor recycling. Some of the extractives in the black liquor precipitated on the pulps in the pretreatment stage, which affected the bleachability of pulps. For softwood, after 5 stages of black liquor recycling, the extractive content of the kraft pulps increased by up to 4 times and the final brightness decreased up to 2.4% ISO. The amount of extractives precipitating on the pulps strongly depended on the final pH of the pretreatment black liquor, which was determined by the operating conditions such as sulfidity, alkali charge, and pretreatment temperature. High alkalinity and low pretreatment temperature was the most efficient combination to minimize extractives from precipitating, and to maintain high bleachability of the kraft pulps. For hardwood, large amount of extractives precipitated onto fibers, and the extractive content, especially the neutral extractive content, of the hardwood kraft pulps was high. During the black liquor recycling, the drop of the final brightness of hardwood kraft pulps was larger than that of the softwood kraft pulps. [ABSTRACT FROM AUTHOR]

Milled wood lignins (MWL) prepared from finely milled world flour produced by different milling techniques were compared by quantitative 13C NMR. Wood meal produced in a Wiley mill was milled for either six weeks in a porcelain rotary mill with porcelain balls, or by two variations of our standard technique. Specifically the Wiley wood meal was milled for one week in the rotary mill followed by 48h of vibratory ball milling with steel balls either in toluene or under a N2 atmosphere. Results showed that the vibratory-milled samples were similar in structure with the exception that the preparation milled under N2 had higher aliphatic and phenolic hydroxyl contents. The rotary milled sample on the other hand had a much lower βO-4′ and hydroxyl content along with a higher degree of condensation and oxidized side chain structures. [ABSTRACT FROM AUTHOR]

The article presents an obituary for scientist Josef S. Gratzl.

Genetic engineering of trees has generated a large amount of interest in the development of highly improved transgenic trees. To efficiently monitor and control the properties of the transgenic products, a rapid, mini-scale analytical method is required. Transmittance near-infrared (NIR) spectroscopy was chosen as a fast analysis tool for characterizing the chemical properties of the transgenic products. Pellets were prepared from 75 mg of wood meal and directly scanned using transmittance NIR spectroscopy. Very strong correlations were obtained between the NIR data and conventional wet-chemistry results for the lignin content, S/G ratio, cellulose and xylose content. The results indicate that transmittance NIR is a powerful tool for determining and screening the chemical properties of transgenic trees. [ABSTRACT FROM AUTHOR]

To better understand the within-tree variations between juvenile wood, mature wood, and compression wood, wood from a 35-year-old mature bent loblolly pine was separated into seven groups by different positions in the tree. Morphological and chemical structure analyses, including fiber quality, X-ray diffraction, sugar and lignin content analysis, as well as nitrobenzene oxidation, ozonation, and advanced NMR spectroscopy, were performed. Fiber properties were significantly different for tree-top juvenile normal wood and tree-bottom juvenile normal wood, juvenile normal and mature normal wood, juvenile compression and mature compression wood. However, differences in the chemical structure and composition were less significant within the specific tissues indicated above. [ABSTRACT FROM AUTHOR]

In conifers, juvenile wood (JW) is always associated with compression wood (CW). Due to their similar properties, there is a common belief that JW is the same as CW. To resolve whether JW is identical to CW, 24 rooted cuttings of one loblolly pine clone were planted in growth chambers under normal, artificial bending, and windy environments. The results show that the morphology of JW is significantly different from CW. Furthermore, chemical analyses revealed that JW and CW are significantly different in chemical composition. Our results indicate that JW is different from CW, and the wood formed under a controlled windy environment is a mild type of compression wood. [ABSTRACT FROM AUTHOR]

The affect of phenolic hydroxyl groups on the reaction efficiency during chlorine dioxide pre-bleaching of a softwood kraft pulp was investigated. The removal of phenolic hydroxyl groups via pulp methylation did not adversely affect the chlorine dioxide bleaching efficiency or the amount of chlorate formed during exposure to chlorine dioxide. Ion analysis of the reaction systems revealed that the formation of chloride and chlorite ions during the bleaching process were very similar between the kraft and methylated kraft pulps. These results indicate that the kinetic rates of lignin oxidation by chlorine dioxide and its reduction products, chlorite and hypochlorous acid, are much faster than the rate of inorganic reactions leading to chlorate formation. [ABSTRACT FROM AUTHOR]

The pulping and bleaching properties of earlywood and latewood of a fast-growing loblolly pine were studied. Under the same pulping condition, the kappa number of the latewood kraft pulp was higher than that of the earlywood. At around the same kappa number, the yield of the latewood was higher than that of the earlywood. The bleaching results showed that the latewood kraft pulp had lower bleachability than the earlywood kraft pulp, due to its thicker cell wall and slower leaching rate. [ABSTRACT FROM AUTHOR]

Features a study that developed a method for the preparation of peroxymonophosphoric acid. Utilization of a biphasic solution to moderate the reaction between phosphorous pentoxide and hydrogen peroxide; Experimental procedure; Results and discussion.