New aspects in cationization of lignocellulose materials. V. Modification of rotten aspen wood meal with quarternary ammonium groups

Holocelluloses prepared from clear and rotten aspen wood were gradually fractionated with 2.5% NH₄OH, 4.5% NaOH, and 17.5% NaOH, respectively. A higher yield of polysaccharides (24.4%) was obtained from the rotten sample in comparison with clear wood (20.9%). Trimethyl ammonium-2-hydroxypropyl (TMAHP) derivatives of rotten aspen were prepared by the reaction of wood with 3-chlor-2-hydroxypropyltrimethylammoniumchloride (CHMAC) in alkaline medium. The quantity of TMAHP—hemicelluloses (yield 14.1%) is only slightly lower in comparison with TMAHP—hemicelluloses (yield 15.8%) obtained by modification and subsequent extraction from clear aspen wood meal. The hemicelluloses isolated from the rotten aspen wood meal are contaminated with low molecular cellulose fraction, the degradation products of cellulose attacked by fungi. The lignin component of rotten wood is less intensively attacked by fungi than the polysaccharidic one.     

New aspects in cationization of lignocellulose materials. VII. Modification of spruce wood meal with quarternary ammonium groups

Trimethylammonium-2-hydroxypropyl (TMAHP) derivatives of spruce wood meal (SWM) and holocellulose of this specia were prepared by the reaction of wood meal with 3-chlor-2-hydroxy-propyltrimethylammoniumchloride (CHMAC) in alkaline medium. The TMAHP samples were fractionated and yields and exchange capacity (Q) of individual fractions were compared with beech and aspen fractions obtained under the same conditions. As it is evident from ¹³C-NMR spectroscopy and GPC analysis the water soluble fraction from TMAHP–SWM consists only of lignin–saccharide degradation products. The NaOH extracts of TMAHP–SWM and TMAHP–holocellulose as well as the water-soluble fraction from TMAHP–holocellulose are polymeric materials. From TMAHP–SWM only 3.1% of alkali-soluble material could be extracted, while from TMAHP–holocellulose 15.7% of water-soluble and 7.9% of alkali-soluble materials were obtained.     

New aspects in cationization of lignocellulose materials. IV. Modification of aspen wood meal with quarternary ammonium groups

Trimethylammonium-2-hydroxypropyl (TMAHP) derivatives of aspen wood were prepared by the reaction of wood meal with 3-chloro-2-hydroxypropyltrimethylammoniumchloride (CHMAC) in alkaline medium. The TMAHP sample was fractionated and yields and exchange capacities (Q) of individual fractions were compared with beech sawdust fractions obtained under the same conditions. The most evident difference between the two studied wood types was the higher yield (14.5% of starting material) of water-soluble TMAHP–hemicelluloses obtained from aspen wood.     

New aspects in cationization of lignocellulose materials. VIII. Modification of immitted spruce wood with quarternary ammonium groups

Immitted spruce wood meal (ISWM) was modified with 3-chlor-2-hydroxypropyltrimethyl-ammoniuchloride (CHMAC) or 1,3-bis(3-chlor-2-hydroxypropyl)imidazoliumhydrogensulphate (BCHIHS) in alkaline medium. The obtained material was gradually extracted with water and 5% NaOH. The yields of water-soluble hemicelluloses modified with quarternary ammonium groups were lower in comparison to healthy spruce material obtained under the same conditions but even more material could be obtained from ISWM-holocellulose. The quantity of alkali-soluble polysaccharides from ISWM was the same as obtained from undamaged spruce. The residues after alkali extractions are suitable ion exchangers with low solubility in dilute alkali solutions. The yields of extracts from material modified with BCHIHS were lower than yields of extracts from material modified with CHMAC because ISWM was crosslinked when alkylated with bifunctional chemicals.     

New aspects in cationization of lignocellulose materials. III. Influence of delignification on reactivity and extractability of TMAHP–hemicelluloses

Beech sawdust samples with different lignin content were alkylated with 3-chloro-2-hydroxypropyltrimethylammoniumchloride (CHMAC). The yields and the degree of subtitution of trimethylammonium-2-hydroxypropyl (TMAHP) samples were similar. Differences were found in extractability of hemicelluloses from this materials both with water and dilute alkali. To obtain the maximum yield of TMAHP–hemicelluloses (ca. 90% of the amount originally present), it is sufficient to remove about 50% of lignin. The lignin component does not influence the reactivity of hemicelluloses. The isolated hemicelluloses differ only in the distribution of functional groups and extractability.     

New aspects in cationization of lignocellulose materials. I. Preparation of lignocellulose materials containing quarternary ammonium groups

TMAHP derivatives were prepared by the reaction of beech sawdust with CHMAC in alkaline medium. The examination of the reaction conditions showed that the most suitable molar ratio was NaOH/CHMAC = 1.8 (1 ml 17.5% NaOH/1 mL 50% CHMAC). At this ratio the maximum degree of substitution expressed by the exchange capacity of 0.35 mmol/g of modified sawdust was obtained by using 1.5–2mL of 50% aqueous solution of CHMAC/g sawdust. The optimal reaction time at 60°C was 2 h. This condition gave yields of modified sawdust above 90% and soluble derivatives mainly consisting of hemicelluloses up to 12%.     

原位复合纳米SiO2改性脲醛木塑复合材料制备

以原位复合纳米SiO2改性脲醛树脂为填充体，人工速生杨木为基体，通过真空加压浸渍法制得木塑复合材料。各种木塑复合材料的主要性能——增重率、抗吸水性、顺纹和恒纹压缩强度分别提高49％、38％、68％和83％。扫描电镜照片显示纳米SiO2改性脲醛完整地填充在杨木基体导管以及孔状结构中。傅立叶红外光谱（FTIR）分析纳米SiO2改性脲醛与杨木基体的固化反应表明，木塑复合材料中木质素C=O吸收峰1750cm^-1完全消失，木质素COO-吸收峰1645cm^-1增强而且发生偏移，充分证明纳米SiO2改性脲醛树脂填充体与木材基体之间发生了化学键合作用而使木塑复合材料各项力学性能得以增强。     

New aspects in cationization of lignocellulose materials. IX. Flame retardancy effect of modification with nitrogen and sulfur containing groups

Lignocellulose materials were modified with 3-chlor-2-hydroxypropyltrimethylammoniumchloride, 1,3-bis(3-chlor-2-hydroxypropyl)imidazoliumhydrogensulphate, and 2-chlorethyl-sodiumsulphonate and the flame-retardant properties of materials obtained were studied. The flame-retardant effect was proved using the limited oxygen index (LOI) method and values up to 32.8 vol % of oxygen were determined. The LOI values were higher when the modification was done without using NaOH for activation, but in that case the alkylating groups were not chemically bonded to the material. The NaOH activation was necessary to obtain material with flame-retardant properties stable against washing. No synergistic effects were observed when the material was modified with both nitrogen- and sulfur-containing groups.     

Alkaline Pre-treatment of Hardwood Chips Prior to Delignification

Abstract

Hardwood (Betula pendula) chips were extracted having alkaline aqueous solutions with varying chemical charges (1, 2, 3, 4, 6, and 8% of NaOH on wood), treatment times (30, 60, 90, and 120 minutes), and temperatures (130°C and 150°C). The total amount of material removed was in the range 2.1–16.5% of the original dry feedstock. This fraction was characterized in terms of carbohydrates and their degradation products (mainly aliphatic carboxylic acids together with some furanoic compounds), lignin, and extractives. Low alkali charges (1–4% of NaOH) were not sufficient to neutralize all the acids formed (mainly acetic acid from the acetyl groups of xylan). In contrast, an increase in alkali charge (6% and 8% of NaOH) more intensively facilitated the alkali-catalyzed degradation reactions of polysaccharides to various hydroxy acids, which were then typically present as one of the main constituents in the dissolved organic matter, along with other aliphatic carboxylic acids (acetic and formic acids), lignin, extractives, and carbohydrates.     

The effect of moisture on the dynamical mechanical properties of bacterial cellulose/glucuronoxylan nanocomposites

The plant cell wall possesses unique material properties due to its hierarchical organisation. In order to biomimic a native structure like a plant cell wall, a model system consisting of microfibrillar cellulose, produced by the gram-negative bacteria Acetobacter xylinum, and a glucuronoxylan matrix derived from aspen holocellulose was constructed. The glucuronoxylan was extracted from delignified aspen (Populus tremula) wood chips using DMSO to preserve its native chemical composition. Dynamic mechanical analysis (DMA) measurements performed with moisture scans showed a moisture-induced softening of delignified aspen wood fibres due to the plasticization of glucuronoxylan. A similar result was observed for the model system. However, the softening behaviour of the delignified aspen fibre and the model system was not identical, most probably due to differences in spatial organisation of the components. Dynamic FTIR-studies indicated that interactions between the cellulose and the glucuronoxylan exist in the aspen holocellulose while the components in the nanocomposite appear to be more isolated.     

Wood Fiber Quality and Kraft Pulping Efficiencies of Trembling Aspen (Populus tremuloides Michx) Clones

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 the starting wood resources (fiber coarseness). These findings suggest that geographic location imparts influences on wood fiber coarseness traits, while substantial genetic variability exists on all sites.     

Liquefaction of aspen poplar wood

Dried and green aspen poplar wood suspended in water containing alkaline catalysts has been converted completely to an oil, water-soluble chemicals and gases if heated for one hour in the presence of carbon monoxide in a rocking batch reactor. Within the ranges of parameters studied: temperature (593—633 K), nominal reaction times (0—1 h), water-to-wood ratio (0.5:1—5:1), catalyst (Na₂CO₃, K₂CO₃, NaOH), amount of catalyst (7.0—12.5 wt %) and initial hydrogen to carbon monoxide ratios (2:1—0:1), the water-to-wood ratio was most important. Oil yields of ?50% with a carbon plus hydrogen content of ?80% and representing a carbon recovery of ?66% were obtained. The higher heats of combustion ranged from 32.2 to 36.0 MJ/kg.     

Characteristics of Dioxane Lignins Isolated at Different Ages of Nalita Wood (Trema orientalis)

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 C₉H_9.31O_3.13(OCH₃)_1.27, whereas that of aspen was C₉H_8.94O_3.15(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.     

碱刻蚀玄武岩纤维对地质聚合物基木材胶黏剂胶接性能的影响

作为新型环保无机胶凝材料,地质聚合物在人造板产业中具有巨大的应用潜力,但地质聚合物的脆性不利于其与木材胶接。本文以改善地质聚合物基体的脆性,增强其与木材胶接强度为目的,采用不同浓度及温度的NaOH溶液对玄武岩纤维(BF)进行碱刻蚀,将碱刻蚀玄武岩纤维(HAF)与碱激发剂共混,制备碱刻蚀玄武岩纤维掺杂的地质聚合物(HAFMG),探究碱刻蚀方法对HAFMG的力学性能及HAFMG与木材胶接强度的影响。结果表明:碱刻蚀处理可溶解BF表面的硅铝组分,提高BF表面粗糙程度及其与地质聚合物基体的界面结合,最终提高地质聚合物与木材的胶接强度。掺入HAF(100 ℃、0.5 mol/L NaOH)可提高地质聚合物基体的韧性,相较于纯地质聚合物,其抗折强度提高了154%,压折比降低了41%。HAF(100 ℃、0.5 mol/L NaOH)掺杂后的地质聚合物与木材的剪切强度相比于纯地质聚合物提高了121%。     

The Characteristics and Reactivity of Acid-Labile Aryl Ether Units in Wood Lignin

Wood lignin contains significant amounts of acid-labile aryl ether units, which play a significant role in lignin modification or delignification processes. We have evaluated the rate and reaction kinetics on the acid-catalyzed cleavages of aryl ether structures for wood lignin in situ based on the formation of phenolic hydroxyl groups. The content of acid-labile aryl ether units was quite uniform for a variety of softwood wood lignins (～4% per C₉ unit) and it varied appreciably among hardwood species, ranging from 4% for aspen to 9% for beech wood lignin. These variations, however, appear to be related to the content of syringyl units in wood lignin. The reactivity of these reactive aryl ether structures was noticeably higher for the spruce than for the aspen wood lignin. This difference in reactivity, based on the behavior of lignin model compound reactions, can be attributed to the influence of syringyl moieties in aspen wood lignin. It appears that most of the acid-labile aryl ether units in hardwood were associated with the syringy moiety being present as a benzyl unit, which is much less reactive than the corresponding guaiacyl moiety.     

Fibreboard from exotic raw materials. Ii. Hardboard from undebarked cotton stalks

It was possible to obtain hardboard of acceptable properties by mechanical pulping of undebarked cotton stalks previously soaked in water at room temperature. Pretreatment of the undebarked cotton stalks with 10–15% NaOH or Ca(OH)₂ at atmospheric pressure for 4 h at 100°C, before mechanical defibration, results in considerable improvement in properties of the hardboard and less added resin requirement. The improvement due to chemical pretreatment is attributed to fibre softening. The semichemical pulps prepared from undebarked cotton stalks had remarkably high freeness compared with rice straw. Bending strength and water resistance are better than those obtained from rice straw and average samples of wood wastes.     

The catalytic steam gasification of chars from various sources by K2CO3

Gasification of a char prepared from hydrocracked residuum was compared with the gasification of chars prepared from bituminous and sub-bituminous Canadian coals, wood and graphite. Each material was mixed with 10 mass per cent K₂CO₃ and pyrolyzed up to 900°C. The yield of char was inversely proportional to the amount of volatile matter in the original material. The char prepared from hydrocracked residuum was different from the others. The other chars all followed zero-order gasification kinetics. Gasification of char prepared from the residuum was first-order in the solid. The development of a liquid phase during the pyrolysis of the residuum to char may explain this difference. The gasification rate of the char. from residuum was slower than the rates with the two coal chars and the wood char, but faster than the gasification rate of graphite. A combination of transient experiments and X-ray photoelectron spectroscopic (XPS) measurements indicated that hydrogen was formed almost instantaneously when steam reacted with the char. XPS spectra at liquid nitrogen temperature indicated that during gasification the formation of carbon oxygen bonds proceeded in the following sequence: COH, CO and CO.     

Extraction and Characterization of Hemicelluloses and Cellulose from Oil Palm Trunk and Empty Fruit Bunch Fibres

Abstract

The cell walls of oil palm trunk fibre and empty fruit bunch (EFB) fibre were initially extracted with 5% NaOH at boiling for 2 h, which removed 17.3% and 15.2% hemicelluloses, respectively. Further extraction of the delignified palm trunk and EFB fibre was conducted with 10% NaOH at 20°C for 16 h and 24% KOH-2% H₃BO₃ at 20°C for 2 h. This resulted in the release of 11.9%, 13.5%, 12.7% and 14.9% residual hemicelluloses, respectively. The cellulose content, isolated by 24% KOH-2% H₃BO₃ from the two fibre samples, was found to be 41.3-41.7%, most of which was relatively free of associated lignin and hemicelluloses. The hemicelluloses, extracted with 5% NaOH from the lignified palm trunk fibre and EFB fibre, contained relatively high amounts of xylose, and minor arabinose and rhamnose than the hemicelluloses, extracted with 10% NaOH and 24% KOH-2% H₃BO₃ from the delignified fibres. While the hemicelluloses, extracted with 10% NaOH and 24% KOH-2% H₃BO₃ from the delignified palm trunk and EFB fibre, contained slightly more galactose, glucose, and mannose than the hemicelluloses, extracted with 5% NaOH from the lignified fibres. Further studies implied that the hemicelluloses, extracted with 5% NaOH from the lignified fibres, were more linear and acidic and had a large molecular size (weight-average, 17,400-22,900), together with comparatively high associated lignins (12.0-15.7%). Which were found to be linked to hemicelluloses mainly via syringyl unit. On the other hand, the hemicelluloses, extracted with 10% NaOH and 24% KOH-2% H₃BO₃ from the delignified fibres, were more branched but less acidic and had a comparatively small molecular size (weight-average, 6,600-10,800), together with trace amounts of associated lignin (0.3-1.1%). The hemicelluloses in the cell walls of palm EFB had a higher degree of polymerizaton than the hemicelluloses in the cell walls of palm trunk fibre as indicated by the molecular-average weights, ranging from 7,200 to 22,900, and from 6,600 to 17,400, respectively.     

Porous carbon materials produced by the chemical activation of birch wood

It was established that the main factors responsible for the yield and specific surface area of porous carbon materials obtained by the chemical activation of the wood of birch are the nature of a modifying agent and the temperature of pyrolysis. The additional opening of the porous structure of the product of the chemical activation of wood occurs at the stage of its water treatment as a result of the removal of water-soluble compounds. The conditions of the carbonization of birch wood modified with H₃PO₄, KOH, and ZnCl₂ were chosen in order to provide the significant development of the porous structure of carbon materials. The porous carbon material with the highest specific surface area (more than 2560 m²/g) was obtained by the water washing of the product of the carbonization of birch wood modified H₃PO₄ at 400°C.     

相转移催化法合成多聚乙二醇二环氧甘油醚

以多聚乙二醇和环氧氯丙烷为原料合成了多聚乙二醇二环氧甘油醚。NaOH为催化剂,季铵盐为相转移催化剂。结论为:作为催化剂NaOH固体效果优于NaOH溶液;四正丁基硫酸氢铵(TBAS)催化醚化反应效果最佳,GC监测表明,二醚的选择性达98％以上;n(多聚乙二醇):n(环氧氯丙烷):n(NaOH):n(TBAS)= 1:10:7:0．08;反应温度55-60℃;反应时间1．5 h;产率83％。