摘要:

The esterification reaction between lignocellulosic materials (ALCELL lignin and Bleached kraft cellulose) and maleated polypropylenes (graft copolymerization of maleic anhydride into polypropylene chains) was investigated. The reaction was conducted in a reactor in the presence of xylene used as a solvent and sodium hypophosphite as a catalyst. The reaction between lignocellulosic materials and pure maleic anhydride was also conducted to determine the effect of the long polypropylene chains on the formation of ester bonds. The XPS studies of maleated bleached kraft cellulose showed the emergence of C4 carbon type on high resolution spectra, which was related to ester carbonyl functionality formed by esterification reaction. No evidence of esterification was observed between ALCELL lignin and maleated polypropylenes. The XPS studies demonstrated that both ALCELL lignin and bleached kraft cellulose chemically react with maleic anhydride with the formation of ester bonds.

ISSN:0277-3813    

DOI:10.1080/02773819809350122

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The feasibility of using FT-Raman spectroscopy for rapid non-destructive determination of hemicellulosic neutral sugar composition, important factors for pulp properties, in native wood was examined using twoEucalyptusspecies, including samples of various ages and colors, which are important sources of plantation pulpwood. The sugars, glucose, xylose, galactose, rhamnose, arabinose and mannose were utilized. The application of 2nd derivatives transformation of Raman spectroscopic data revealed highly significant correlations between wet chemical and Raman predicted values in the calibration (known samples) with correlation coefficients > 0.99, and in the prediction (unknown samples) with correlation coefficients > 0.80 with the exception of rhamnose and mannose. Consequently, this non-destructive method will be valid for analyzingEucalyptusnative wood meal samples, regardless of their age and color to determine hemicellulosic neutral sugar composition except rhamnose and mannose. Elite tree selection based on quality aspects for pulp and paper production can be performed using FT-Raman spectroscopy.

ISSN:0277-3813    

DOI:10.1080/02773819809350123

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The feasibility of using FT-Raman spectroscopy for rapid non-destructive determination of lignin syringyl/guaiacyl (S/G) monomeric composition was examined usingEucalyptus camaldulensisandE. globulus, including samples of various ages and colors, which are of importance as a plantation source. The application of 2nd derivatives transformation of Raman spectroscopic data revealed highly significant correlations between wet chemical and Raman predicted values with correlation coefficient (r) = 0.998 and standard error of prediction (SEP) < 0.07 points in the calibration (for known samples), and r = 0.935 and SEP < 0.32 points in the prediction (for unknown samples), respectively. Consequently, this nondestructive method has proved its validity for analyzingEucalyptusnative wood meal samples, regardless of their age and color to determine lignin S/G monomeric composition. Using FT-Raman spectroscopy, elite tree selection based on quality aspects for pulp and paper production can be performed.

ISSN:0277-3813    

DOI:10.1080/02773819809350124

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Pre-extracted radial sections of southern yellow pine sapwood were treated with CCA-C and analyzed by x-ray photoelectron spectroscopy (xps). The ratio of CI (carbon bonded only to carbon and/or hydrogen) to C2 (carbon bonded to one oxygen with a single bond) was used to determine the progress of oxidation of wood components during CCA fixation. This ratio increased after treating times of 10 minutes and 60 minutes and decreased after 180 minutes soaking suggesting that oxidation of C2 predominates on initial contact with CCA solution but oxidation of CI (lignin) becomes more important with extended exposure to the treating solution. Oxidation of C2 to C3 (carbon bonded to two oxygens or a carbonyl group) was demonstrated byin situtrapping of C3 with ethylene glycol as it was formed. Further oxidation of C3 to C4 (carboxylic carbon) was not observed in the xps spectra, consistent with the findings of others. The hypothesis that rapid decarboxylation results in loss of C4 as evolved CO2is supported by the observation that the C4 component of untreated wood was reduced by more than 90% after 10 minutes of CCA soaking followed by high temperature fixation and by the observation of CO2evolution during early stages of accelerated fixation. The Cr(2p) spectra of CrVIand CrIIIwere established at 580.2 and 577.8 eV respectively. Accelerated fixation of CCA-C treated specimens resulted in a very high degree of reduction of CrVIto CrIII. XPS Cu (2p3/2) peaks were established at 935.1 for CCA-C, 935.3 for Cu(OH)2, and 933.7 for CuO. Cu (2p3/2) peaks in CCA-treated wood were shown at 932.9 with no satellite peaks for the 10-60 minutes soaking in CCA series, and at 933.9 and 936.4 with satellite at 941-948 for the 3 hours soaking time. The latter are attributed to complexed copper oxide and hydroxide forms of CuII. Peaks attributed to CuIIhydroxides were shown to diminish in leached samples.

ISSN:0277-3813    

DOI:10.1080/02773819809350125

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Kraft and soda delignification kinetics of wheat straw,Triticum aestivum, have been studied as a function of OH “concentration, HS” concentration, and temperature. It was found that about 90% of the lignin is dissolved in the rapid initial phase. The rates of delignification in the bulk and residual phases were found to be similar to those of birch wood,Betula pubescens.The amount of residual phase lignin was found to be considerably less than in birch or spruce,Picea abies, and it was affected by the same factors, A model that accurately describes the delignification of wheat straw was derived.

ISSN:0277-3813    

DOI:10.1080/02773819809350126

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A kinetic model of peracetic acid brightening of a solvent-assisted ozone delignified pulp was developed. The model consists of three parallel and one consecutive reaction, and is based on reaction pathways reported for lignin model compounds with peracetic acid. An optimization search algorithm was used to find the kinetic parameters of the model. The kinetic model provides an adequate description of the disappearance rate of the chromophores in pulp at constant pH and peracetic acid concentration.

ISSN:0277-3813    

DOI:10.1080/02773819809350127

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The title compound (2) was degraded at 150-180°C in oxygen-free 0.5-2.5M aqueous NaOH. Degradation occurred by cleavage of both the glycosyl-oxygen bond (80-95%) and the oxygen-aglycon bond (5-20%). Cleavage of the glycosyl-oxygen bond yielded 1, 5-anhydro-2, 3, 6-tri-O-methyl-D-glucitol (5) from the aglycon. The reactive intermediate, 1, 6-anhydro-β-D-glucopyranose, was formed from the glycosyl moiety in amounts (50-88%) dependent upon the reaction conditions. Cleavage of the oxygen-aglycon bond resulted in unidentified products, probably acidic and fragmentary in nature and quantified as a mass deficit. Data for cleavage of the glycosyl-oxygen bond is consistent with an SNicB(21) mechanism while that for oxygen-aglycon bond cleavage is consistent with an SN1 mechanism.

ISSN:0277-3813    

DOI:10.1080/02773819809350128

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor