摘要:

Brown rots from various conifer species were sieved (&lt60 mesh) and alcohol and water extracted to yield crude preparations of “naturally enzymatically liberated lignin” (NEL) containing 61.4–91.7Z of Klason plus soluble lignin and 0.5–2.6% ash. The <200 mesh fractions were generally best represented in <60 mesh preparations and contained highest Klason plus soluble lignin percentages (86.6–92.2Z). Carbohydrates varied in these fractions between 3.7 and 8.0% and contained glucose, mannose, galactose, xylose, and arablnose, decreasing generally in that order. Methoxyl contents were lower and oxygen contents higher than in milled wood lignin (MWL) suggesting some oxidative demethylation. Treatment with Cuoxaa increased Klason plus soluble lignin content to 93.0–95.8%, decreased carbohydrates to 1.7–5.0%, increased methoxyl and decreased oxygen contents by removal of a part of cellulose and hemicelluloses and of more degraded lignin fractions. Infrared spectra of the preparations showed a small increase in carboxyls and possibly in phenyl conjugated double bonds and a decrease in aromatic structures, as compared with MWL. In thermo-gravimetric analysis the curves for MWL and Cuoxam treated NEL preparations (CuNEL) were very similar when run in nitrogen. In air, however, MWL lost weight appreciably slower. In differential scanning calorimetry in air and oxygen, MWL exhibited less intensive exotherms below 500°C than NEL and left higher amounts of char. The different behaviour of MWL in thermal analysis in oxidative atmosphere was explained by its lower molecular weight and corresponding low glass transition temperature (Tg). It was concluded that preparation of enzymatically liberated lignin from natural brown rot represents a convenient procedure where larger amounts of lignin are required; such lignins are somewhat more degraded than MWL in terms of functional groups present, but are possibly closer to protolignin in terms of molecular weight.

ISSN:0277-3813    

DOI:10.1080/02773818208085140

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The spin–lattice relaxation times (T1) of the twelve most abundant carbon atoms in acetylated milled wood lignin (MWL) from hazelnut (Corylus avellanus) have been determined by the progressive saturation pulse Fourier transform (PSFT) technique. T1values below 0.5 s have been found for the aliphatic carbon atoms in the C3side chains, while substituted aromatic, carbonyl and CH3carbon atoms in methoxy and acetyl groups have T values ranging between 1 and 3 a. From these results a quantitative determination of interunit linkages in lignin may be possible from car-bon-13 spectra with pulse interval times of at least 3 s.

ISSN:0277-3813    

DOI:10.1080/02773818208085141

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Coniferyl alcohol is the major building block of softwood lignin. Although its formation in the cooking liquor during kraft pulping is predicted by the proposed mechanism, it has not been previously found at any appreciable concentration during alkaline delignification. The reason for this is its instability in hot caustic liquors I have observed the formation of coniferyl alcohol at suprisingly high concentrations as a transient product of delignification of softwood chips in soda, sodaanthraquinone (AQ), kraft and kraft-AQ pulping under normal conditions. Higher yields were obtained with woodmeal than with chips. The maximum concentration is reached at the end of the initial delignification phase during the rise-to-temperature and is particularly dependent on the nature and quantity of additives such as Na2S, AQ and anthraquinone mono-sulphonate. This observation supports the proposed mechanism of alkaline delignification and is, in fact, the first evidence of this mechanism based on wood rather than model compounds.

ISSN:0277-3813    

DOI:10.1080/02773818208085142

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A mechanism previously proposed for the formation of 3-guaiacylbenzanthrone in anthraquinone pulping cooks is investigated and discussed. Some implications for AQ loss and recoverability are also briefly discussed.

ISSN:0277-3813    

DOI:10.1080/02773818208085143

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Wood meal and chips of pine (Pinus sylvestris) were pretreated with oxygen in ethanol-water solutions of sodium hydroxide and then subjected to soda-anthraquinone pulping. It was found that the pretreated wood was delignified much faster than the untreated wood. Additional effects were the improved yield and higher brightness of the resulting pulp. The delignification could be extended nearly to the same kappa number as by kraft pulping and subsequent oxygen bleaching (about 15), although the viscosity of the pulp was comparatively low. The effect of pretreatment and pulping conditions on the delignification and carbohydrate yield is discussed.

ISSN:0277-3813    

DOI:10.1080/02773818208085144

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Several commercial thermomechanical pulps and stone ground-wood pulps were bleached to determine how the bleaching rate is affected by peroxide and alkali concentration, pulp consistency and temperature. The bleaching rate seems to be determined by the balance between the bleaching action of peroxide anion (HO) and color formation by alkali (OH). At a given peroxide concentration, increased alkalinity increased the bleaching rate due to the formation of peroxide anion, up to a given alkali concentration above which a further increase led to a decrease in reaction rate. This is probably due to the fact that at high alkalinity, pOH < 2.5, an increase in hydroxide ion concentration gives only a slight increase in the peroxide anion concentration, at lower alkalinity, the increase in peroxide anion concentration is approximately proportional to that of the hydroxide ion.

ISSN:0277-3813    

DOI:10.1080/02773818208085145

出版商:Taylor & Francis Group    

年代:1982

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:10.1080/02773818208085139

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor