摘要:

The degradation of dioxane lignin with oxygen in alkaline aqueous ethanol was studied. An increase in the ethanol concentration resulted in an accelerated degradation of lignin. Separate experiments with creosol (2-methoxy-4-methylphenol) indicated that this effect can at least partly be ascribed to the inhibition of the coupling of phenoxy radicals, which prevents the recondensation of the lignin fragments.

ISSN:0277-3813    

DOI:10.1080/02773818808070686

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Catalytic degradation of aspen lignin under initially alkaline conditions has been studied as a method of selective conversion of the lignin polymer into potentially valuable phenolic chemicals. In contrast to initially neutral conditions, degradation is not dependent on the presence of molecular hydrogen and relatively larger amounts of C6-C-C over C6-C-C-C degradation products are obtained. The addition of anthraquinone to a typical soda pulping process results in a twofold increase in the yield of monomeric lignin products.

ISSN:0277-3813    

DOI:10.1080/02773818808070687

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The Organocell process is the most advanced organosolv pulping process on a semi-technical scale. Delignification is performed by two-stage cooking involving methanol/water in the first stage with additional NaOH in the second stage. In this study spruce and pine lignins from the Organocell pilot plant and from laboratory cookings in a 20 1 batch digester were characterized by means of elemental analysis, determination of nonlignin portions such as proteins, sugars and ash, and of functional groups (OH, CO, COOH, OCH3). While first stage samples contained a considerable amount of impurities identified as organic nonlignin substances, second stage lignins showed characteristic changes in elemental composition and functional groups, except for the methoxyl groups, as reaction time progressed.

ISSN:0277-3813    

DOI:10.1080/02773818808070688

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Three series of chain-extended hydroxypropyl lignins (CEEQLs), prepared fran oqanosolv and kraft lignin, were examined regarding their chemical, molecular weight and them1 characteristics. Results showed that the molar substitution (MS) of propylene oxide, which was defined as the number of propoxy repeat units which comprise the chain attached to a single reactive site on lignin, varied and affected copolymer properties. As the MS increased from 1 to 7.2, the number average molecular weight (Mg) increased while the glass transition temperature (Tg) decreased. The actual Mgobserved by GPC exceeded however that expected on the basis of mass gain by derivatization. This was attributed to changes in the apparent hydrodynamic volume in relation to MS. The change in Tgwith increasing MS followed the Gordon-Taylor relationship. Differences in the chemical composition of the original lignin (organosolv or Kraft) were not obvious as the lignin content of the copolymer decreased below 50%.

ISSN:0277-3813    

DOI:10.1080/02773818808070689

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A flow scheme was devised for the fractionation-purification of sludge lignin material (mixture of hardwood and softwood) used in the synthesis of a hardboard adhesive. Infrared spectroscopy, proton and carbon-13 nuclear magnetic resonance spectroscopy was used to assign the structure of the sludge lignin. The structural characterization indicated appreciable bond cleavage-rearrangement, and subsequent generation of additional acidic/ketone linkages, p-hydroxyphenyl units and saturated hydrocarbons. Additionally, the sludge lignin based extracts showed good adhesive bonding properties when used in a blend.

ISSN:0277-3813    

DOI:10.1080/02773818808070690

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A two-stage procedure for pretreatment of fast-growing willow with steam has been investigated. The first stage was performed at temperatures in the range 180°C to 220°C for times between 6 and 10 minutes while the second stage was performed at 220°C for 10 minutes.

ISSN:0277-3813    

DOI:10.1080/02773818808070691

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The inner and outer barks of ponderosa pine (P. ponderosa) have been pyrolysed at 350°C in vacuum and the tars analyzed by gas chromatography after tri-O-methylsilylation. The nine major peaks in the gas chromatogram have been identified and quantified and it is concluded that all (except pinitol) originate predominantly from polysaccharide components of the barks. They account for up to 53% of the total tar. Removal of most of the metal ions from the barks by ion exchange with dilute acid has a dramatic influence on the tar constituents, e.g. increasing the yield of levoglucanosan from inner bark from 0.8% to 13%. which represents 31% of the original glucan content of the bark. The polyphenol and lignin components of the bark are predominantly converted directly to char at 350°C.

ISSN:0277-3813    

DOI:10.1080/02773818808070692

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The amount of southern pine lumber treated with chromated copper arsenate annually is considerable, yet the association of this preservative with the wood structure is not clear. The current study was undertaken to elucidate the nature of chemical reactions occurring between the components of the treating solution and the constituents of wood. Small, clear Southern pine samples were treated with six different preservative solutions (Cr; Cr/Cu; Cr/As; CCA-A; CCA-B; CCA-C), at 6.4 and 40 Kg/m3(0.4 and 2.5 pcf) retentions, and compared to water treated and untreated controls. Samples were dried following treatment and analyzed by X-ray photoelectron spectroscopy (XPS). Evaluation of XPS data indicated that the preservative components reacted with wood, through aromatic and possibly alkene substitution, while oxidation of hydroxyl groups was not detected. The proposed wood/CCA bonding also offers an explanation for differences in hardwood and softwood durability following treatment.

ISSN:0277-3813    

DOI:10.1080/02773818808070693

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0277-3813    

DOI:10.1080/02773818808070685

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor