摘要:

SummaryThe influence of acetone, as a solvent on crystalline structure of the cellulose, was investigated. Crystalline changes brought about by the solvent treatment on the residual cellulose have been foundto be noticable. The crystallinity index of solvent treated celluloses has shown a trend of a small gradual increase with the progressive increase of acetone concentration in the treatment. The crystallite size of the residual cellulose has also been found to decrease successively with the increase of acetone content in the solvent composition. While the decrease in crystallite size reached approximately 8 %, the equivalent weight loss was only about 0.9 %.The influence of kinetic parameters on crystalline structure of cellulose during solvent purification (e. g., temperature, reaction time, acidity and type of acid catalyst) was also examined. Acidity and acid catalyst type were found to contribute to crystalline structural changes of cellulose. The use of higher concentrations for acids (TFA, HCl) has led to a decrease in crystallite size and crystallinity index. However, lower concentrations of TFA have a positive impact on the crystallinity index of the treated cotton cellulose. The crystallinity index of the residual cellulose has shown a slight increase with the increase in temperature, while the crystallite size has indicated a successive decrease. The reaction time has offered, in general, better chances for enhancement of the crystallinity index of the cellulose.

ISSN:0018-3830    

DOI:10.1515/HF.1999.001

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

摘要:

SummaryA special furnace for smoke-heating logs, with increased far-infrared radiation (FIR), was produced to improve the wood quality. Green sugi (Cryptomeria japonicaD.Don) logs were smoke-heated with the direct use of this system. In a short time, this process increased the temperature inside the logs up to 80–100 °C uniformly, without any damage to the wood. The great increase in steam pressure inside the log resulted in the rupture of pit membranes (PMs) with a high frequency, leading to a decrease in the moisture contents of the logs. It was found that when a temperature of 80 °C is attained inside the log, the rupture of PMs occurs. The rupture proceeds from the outer sapwood towards the pith, accompanied by the radiation heat transfer within the log. By the rupture of PMs, smoke-heated sugi wood showed a large improvement in permeability.

ISSN:0018-3830    

DOI:10.1515/HF.1999.002

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

摘要:

SummaryA laboratory evaluation was conducted to study the effectiveness of a biotreatment for deresinating wood chips from aged aspen. This treatment involves inoculating chips with a fungal inoculum, Cartapip97®that feeds on wood resin components. This study demonstrated that, at room temperature and at 5°C, Cartapip can colonize chips from aged aspen despite the lower extractives content of the wood.Fungal treatment resulted in an additional 8% removal of wood resin in treated chips than in untreated chips after 3 weeks of seasoning. Analysis of the extractives by gas chromatography showed asignificant reduction of steryl esters (25%), which are troublesome non-saponifiable wood resin components often found in aspen pitch deposits. The fungal treated chips were brighter than theuntreated chips because the fungus prevented colonization of the chips by staining fungi. These results imply that fungal treatment of aspen chip piles in the winter will reduce the amount of wood resin inthe chips and maintain their brightness. Such treatment will help alleviate pitch deposition problems attributable to aspen wax and reduce bleaching costs.

ISSN:0018-3830    

DOI:10.1515/HF.1999.003

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

摘要:

SummaryThe mechanism of wood degradation by white-rot fungi is not understood in detail other than it is involving phenol oxidases (which are lignin-degrading enzymes) and cellulases. The possible role ofhydroxyl radicals in degradation by the white-rot fungusPhanerochaete chrysosporiumwas studied. The production of a low-molecular-weight substance that is secreted was measured periodically. Thesubstance catalyzes a redox reaction between O2and an electron donor producing hydroxyl radicals in the culture fluid of this fungus with glucose or wood as the carbon source. We examined thepossible role(s) of one-electron oxidation activity by phenol oxidases and hydroxyl radicals in wood degradation by this fungus. Assays of phenol oxidase activity showed thatP. chrysosporiumproduced much manganese peroxidase in wood culture, and that the activity peaked early in incubation. Thegeneration of hydroxyl radicals in the redox reaction was related to the rate of wood degradation, but the activity of phenol oxidases was not related. Therefore, hydroxyl radicals are important inwood degradation by this fungus.

ISSN:0018-3830    

DOI:10.1515/HF.1999.004

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

ISSN:0018-3830    

DOI:10.1515/HF.1999.005

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

摘要:

SummaryChemical analysis ofCistanche deserticolashowed the presence of 7.5% of Klason lignin. Different lignin-carbohydrate fractions have been isolated from the methanol pre-extracted and depectinatedCistanche drug by sequential extractions using dioxane-water, cold and hot water, and 4% NaOH solution.13CNMR spectroscopy in combination with sugar analysis were used to characterize the isolated fractions. The proportions of the guaiacyl-, syringyl- andp-hydroxyphenyl units in the lignin-rich fractions differ significantly from those of both hardwood and softwood lignins andresemble more those of gramineous lignins. The carbohydrate portion consists of xylan, starch, pectic polysaccharides, and cellulose in proportions which are not typical of wood tissues.

ISSN:0018-3830    

DOI:10.1515/HF.1999.006

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

摘要:

SummaryRefluxing oftrans–2-(3,4-dimethoxyphenyl)-3-hydroxymethyl-7-methoxy-2,3-dihydrobenzo[b]furanwith dioxane-water (9 : 1) in the presence of various acid catalysts led to the formation of 2-(3,4-dimethoxyphenyl)- 7-methoxy-3-methylbenzo[b]furan, thetransandcisforms of 2-hydroxy-3,3′4′-trimethoxystilbene andcis–2-(3,4-dimethoxyphenyl)-3-hydroxymethyl-7-methoxy-2,3-dihydrobenzo[b]furan.The proportions of the products were strongly dependent on the particular acid used as catalyst. HCl and to a greater extent HBr favored the formation of the 2-arylbenzofuran (phenylcoumarone) while thetrans-stilbene derivative predominated in reaction products from the experiments with trifluoromethane sulfonic acid as the catalyst. Isomerization of the starting material occurred, regardless of the nature ofthe catalyst (small amounts of thecis-isomer formed). The number of phenylpropane units in spruce lignin attached to an adjacent unit by a β−5 linkage was estimated to be 6–9% on the basis of1H NMR spectrometric measurements of the formation of phenylcoumarone structures on refluxing of milled woodlignin from spruce with 0.1M HBr in dioxane-water (9 : 1).

ISSN:0018-3830    

DOI:10.1515/HF.1999.007

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

摘要:

SummaryThe α-hydroxyl group in lignin model compounds 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol (1) and 1-(4-hydroxy-3-methoxyphenyl)ethanol (3), and the α-carbonyl group in 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)ethan-1-one (5) are removed by treatment of the model compounds with trifluoroacetic acid (CF3CO OH) and triethylsilane (Et3sih) in methylene chloride. The reaction is highly chemoselective and it tolerates the lignin γ-hydroxyl group, phenoland β-O-4-aryl ether linkage. The α-hydroxyl group in1has also been removed with triethylsilane in aqueous trifluoroacetic acid (CF3CO OH : H2o = 75 : 25).The combination of trifluoroacetic acid and sodium borohydride, or sodium triacetoxyborohydride, is also effective in removing the α-carbonyl group in5and the α-hydroxyl group in lignin model compound 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)ethanol (7) and in milled wood lignin. The selective removal of the lignin α-hydroxyl and α-carbonyl groups may potentially be used, inconjunction with the protection of the lignin phenol, to inhibit the light and/or heat-induced yellowing of mechanical pulps.

ISSN:0018-3830    

DOI:10.1515/HF.1999.008

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

摘要:

SummaryA detailed examination was made of the behavior and distribution of ash and silica during atmospheric acetic acid pulping and subsequent bleaching of rice straw. Ash-rich pulps (in unbleachedpulp, about 18%; and in bleached pulp, 16%) with matchable strength properties for conventional alkaline pulps were obtained from rice straw by acetic acid pulping. More than 50% of the ash andabout 75% of the silica in rice straw were retained in the pulp after pulping. Because only those acid-soluble mineral components were dissolved during acetic acid pulping, the ash remained in thepulp consisted mainly of silica (92.9% of the ash in unbleached pulp and 97.3% of the ash in bleached pulp). Although part of the ash dissolved during bleaching, the ash content of bleached pulpwas still 15.5%, a value much higher than that in other conventional pulps. This type of ash might be good as a filler for paper. Fractionation analysis and the profile and mapping of silica by scanningelectron microscope combined with an energy dispersive X-ray analysis (SEM-EDXA) indicated that the silica in the bleached pulp was located mainly in epidermal cells and not in other elements, suchas fibers and parenchyma, and that the silica-rich epidermal cells were scattered throughout the pulp as single cells or in bundles.

ISSN:0018-3830    

DOI:10.1515/HF.1999.009

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter

摘要:

SummaryThe chemical composition of suberin was studied in cork planks from three different trees of SpanishQuercus suberat four different stages of the industrial processing of first transformation: stripping (a), first rest (b), boiling followed by open air rest (c1) and boiling followed by store-room rest (c2). Themonomeric composition was determined by gas chromatography/mass spectrometry in the product of depolymerization of the free of extractives cork with sodium methoxide-methanol. The averageconcentrations of the main monomers were: 1-alkanols (C20–C26) 4.17 %; alkanoic acids (C20–C26) 5.99%; α, ω-alkanedioic acids (C16–C24) 6.20%; ω-hydroxy-alkanoic acids (C20–C26) 29.41%;erythroandthreo-9,10-dihydroxyoctadecanedioic acids 6.76%,erythro-andthreo-9,10,18-trihydroxyoctadecanoic acids 9.50%, 9,10-epoxy-18-hydroxyoctadecanoic acid 2.72% and 9,10-epoxy-octadecanedioicacid 2.93% and ferulic acid 5.05%. Significant differences were observed between samples taken at the stripping and after boiling with store room rest, and both groups of samples differed from thosepicked after the other two processing stages. Ten components were selected as providing the greatest discrimination among stages: 9-octadecenedioic, 18-hydroxy-9-octadecenoic, eicosanedioic and 9,10-epoxy-18-hydroxy-octadecanoic acids, tetracosanol, and five unidentified components.

ISSN:0018-3830    

DOI:10.1515/HF.1999.010

出版商:Walter de Gruyter    

年代:1999

数据来源: Degruyter