摘要:

The rate of stabilization of hydrocellulose and glucose against alkaline degradation by hydrogen sulfide was studied as a function of pH and H2S-concentration. The rate of this reaction increases to a maximum with an increase in pH from 3.5 to 6.3. The maximum rate is significantly enhanced by the presence of ammonia base. With increasing H2S-concentration, the stabilization rate increases in a sigmoidal manner. It is demonstrated that this kinetic pattern is in full accordance with the reaction mechanism proposed by Procter involving conversion to a thioalditol via a gem-dithiol intermediate.

ISSN:0277-3813    

DOI:10.1080/02773818408062280

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

During treatment of birch meal with nitric oxide and oxygen methanol was produced at high rate even when only 2% of the added nitric oxide was present as nitrogen dioxide and nitric oxide. This confirms that nitrogen dioxide was regenerated in a reaction cycle. A high temperature and a large addition of nitric oxide favored the regeneration.

ISSN:0277-3813    

DOI:10.1080/02773818408062281

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The extent of anthraquinone (AQ) penetration into handcut Norway spruce chips as a function of cooking time was examined through the combined use of14C-label-led AQ and various wood sectioning techniques. The results indicated that in the initial stage of the cook, the AQ was deposited mainly at or near the chip surfaces in contrast to the alkali which penetrated to the chip core. With increasing cooking time, free and/ or combined AQ concentration at the transverse surface of the chips first decreased then increased both in this region and in the chip interior. This non-uniform distribution of AQ and alkali within the chips during the initial stage of pulping was also manifest by the Kappa number which increased significantly in proceeding from chip exterior to core.

ISSN:0277-3813    

DOI:10.1080/02773818408062282

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The effectiveness of various metal ion complexes of mesotetra (p-sulphophenyl)porphyrin (TSPP) and 4, 4′, 4″, 4″ -tetrasulphophthalocyanine (TSPc) as alternatives to anthraquinone (AQ) as catalysts of alkaline pulping have been evaluated. Using lignin model compounds two of the complexes, Co-TSPP and Fe-TSPc, were found to increase the amount of β-ether cleavage more than AQ. The yield of guaiacol was also increased significantly by increasing the amount of glucose in the controls. Evaluation of the potential of Co-TSPP as a catalyst for the soda pulping of Pinus radiata showed that the complex does promote delignification but not as well as AQ. As with the AQ the pulp yields were higher than the corresponding soda controls. The increased yields, the need for a reducing source, and the formation of vinylguaiacol as a co-product in the model compound studies indicate that the complexes may operate in a similar manner to AQ.

ISSN:0277-3813    

DOI:10.1080/02773818408062283

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The ability of hydroxide Ion to produce carbanlons at 170°C In water has been determined by measuring the extent of deuteratlon and reexchange of deuterium labels for several organic acids and phenols. The results of the exchange reactions provide a rough estimate of the types of reactions that are possible between hydroxide Ion and wood components during alkaline pulping. It has been estimated that NaOH/H20 at 170° can deprotonate organic acids having pKavalues of about 35 and can produce polyanlon intermediates. Several experiments were directed toward understanding the effects of ct-hydroxyl groups and zinc ions on carbanion formation. Exchange reactions involving Na2S at 170° showed that this species is largely dissociated to NaOH and NaSH and that the latter does not contribute to the basicity of the solution.

ISSN:0277-3813    

DOI:10.1080/02773818408062284

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The densities of acid-chlorite delignified Asplund spruce fibres with degrees of delignification between 0 and 62.4 % were determined. The density measurements were carried out at 23 C in mixtures of carbon tetrachloride and toluene, using a density gradient column. The density of the dry fibres increased linearly with decreasing lignin content and the density of lignin and holocellulose in situ were found to be 1397 and 1541 kg/m3respectively. Assuming a density of 1559 kg/m3for a-cellulose, the density of hemicellulose in situ was calculated to be 1520 kg/m . The physical implications of the measured values are discussed. It is concluded that there is no change in the density of holocellulose or lignin between 20 and 62.4 % delignification. It is suggested that the densification of the fibre during the initial stage of delignification is due to increased order in the hemi-celluloses.

ISSN:0277-3813    

DOI:10.1080/02773818408062285

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Rapid steam hydrolysis of wood chips with continuous condensate/product removal was investigated as a biomass pretreatment similar to steam explosion. Steam was introduced at the top of a pressurized reactor containing mixed southern hardwood chips while steam condensate and partible products were removed at the bottom of the reactor. A reaction time of one minute was employed for isothermal steaming runs from 160-280°C. Fractionation of wood occurred at temperatures above 200°C as hemicellulose and lignin began to appear in the steam condensate fraction, leaving a cellulose-rich fraction in the steaming reactor. At high temperatures cellulose was not degraded as much as it was in steam explosion at the same temperature, presumably due to the removal of acetic acid as it is formed. Lignin extracted from the solid residue appeared particularly reactive as determined by nitrobenzene oxidation and pyrolysis/gas chromatography. Lignin collected in the steam condensate was also very reactive, presumably due to its rapid cooling after being removed from the reactor.

ISSN:0277-3813    

DOI:10.1080/02773818408062286

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

This Conference will be held July 2-6, 1984 at Brewster Academy, Wolfeboro, New Hampshire. Among the topics to be discussed are the following: solid stateiJC NMR spectra of celluloses, ultrastructure ofcellulose fibers - some new aspects, plant cell wall polysaccharides, 13 structural C NMR studies of lignin and lignin-like materials from flash utohydrolyzed wood, isolation of lignins from wood, electron transfer reactions in lignin and pulping chemistry, and structural inhomogeneity of lignin in wood cell walls.

ISSN:0277-3813    

DOI:10.1080/02773818408062287

出版商:Taylor & Francis Group    

年代:1984

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:10.1080/02773818408062279

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor