摘要:

The enzymatic digestibility of the softwoodPinus radiatais substantially enhanced by SO2-catalysed steam explosion. The factors controlling the effectiveness of this pretreatment have been studied. Under conditions of constant time (3 minutes) and temperature (215°c) the effects of SO2-impregnation levels from 0–11.8% were examined. Up to about 3% SO2there is a pronounced effect on the enzymatic digestibility of the pretreated substrate and a rapid increase in the yield of water soluble sugars. At 2.55% SO2, a total sugar yield of 57.4 g/100 g oven-dry wood was obtained. SO2levels above 3% had no beneficial effects in terms of increased sugar yields. Equivalent total sugar yields could be obtained by shortening the treatment time to 1 minute and increasing the temperature to 235°c (still at 2.55% SO2). Percentage solubilisation of wood glucan correlates strongly with the enzymatic digestibility of the pretreated substrate and also with the surface area accessible to a 51Å molecule. This suggests that carbohydrate solubilisation and cell wall accessibility are closely related. The major, beneficial effect of SO2during steam explosion ofP. radiatais to promote hemicellulose and cellulose hydrolysis while limiting excessive carbohydrate degradation. However, sugar reversion products were observed under near-optimal treatment conditions, this being an undesirable consequence of SO2catalysis. Evidence is presented suggesting a very low level of lignin sulphonation and consequently very little soluble lignin is produced. The almost total retention of lignin in the pretreated substrate appears to present little hindrance to the enzymatic digestion of its cellulose component.

ISSN:0277-3813    

DOI:10.1080/02773818908050291

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Hybrid poplar lignins were isolated from selected hybrid poplar clones by an enzymatic/solvent extraction method. The lignins were subjected to both rapid hydrothermolysis (RHT) and alkaline hydrolysis. Phenol (C6H6OH) was the predominant component of hydrothermolysis products, whilst p-hydroxybenzoic acid (PHBA) was the chief product of the alkaline hydrolysis. Phenol yields were 2–9 wt.% of the lignin, whilst PHBA yields ranged from 3–6 wt.% of the lignin. The yields of both products were sensitive to the poplar clone. When PHBA was similarly subjected to the RHT process, it decarboxylated to phenol quantitatively. Thus the phenol observed in the RHT products derives mostly from the PHBA esters in the lignin. The PHBA is linked to the lignin by ester and/or ether bonds. PHBA linkages are cleaved hydrolytically and the resultant acid then decarboxylates to phenol.

ISSN:0277-3813    

DOI:10.1080/02773818908050292

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Size Exclusion Chromatography/Low Angle Laser Light Scattering (SEC/LALLS) has been used to monitor changes in the molecular weight disbribution (MWD) of lignins recovered from alkaline pulping liquors. While developing a method of molecular weight analysis, we discovered that fluorescence was contributing to the detected signal. During the course of the experiments, we realized that this laser-induced fluorescence, could be used to monitor lignin. We modified the filters in the LALLS instrument and sucessfully measured lignin fluorescent properties. We found that fluorescence of lignin increased during the course of pulping with the formation of fluorescent structures excited at the wavelength of the laser (632.8 nm) being uniform throughout the molecular weight range.

ISSN:0277-3813    

DOI:10.1080/02773818908050293

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The number average structure and the molecular weight distribution of phenol-formaldehyde prepolymers for use in synthesis of tannin-based adhesive resins were determined with1H- and13C-NMR spectroscopy and gel permeation chromatography of acetylated resins. These methods were used to determine differences in phenol-formaldehyde prepolymens prepared under different reaction conditions. Quantitative13C-NMR techniques provided a detailed analysis of the structure of a phenol-formaldehyde prepolymer.

ISSN:0277-3813    

DOI:10.1080/02773818908050294

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Solid-sample carbon-13 NMR spectroscopy with cross polarization and magic angle spinning (CP/MAS) was employed to study the hydroxymethylation of lignin. Kraft pine and steam-exploded hardwood lignins were reacted with formaldehyde and the resultant structural changes in the lignins evaluated by comparing the spectra of the treated and untreated lignins. The results indicated that hydroxymethylation had occurred at the 5 position of phenolic guaiacyl units, in keeping with known reactions for phenol-formaldehyde resole formation. The degrees of formaldehyde substitution determined from CP/MAS NMR spectra were in excellent agreement with those determined by other methods. Intensities in the untreated kraft pine lignin spectrum implied the presence of unsaturated sidechains with some loss of γ carbons.

ISSN:0277-3813    

DOI:10.1080/02773818908050295

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

13C CP/MAS NMR spectra of birch pulp samples were measured at regular intervals during the kraft pulping process. General multivariate data analysis methods based on principal components were used to extract the spectral information content and to relate these components to chemical descriptors such as lignin content. It was shown that this approach has an improved predictive ability relative to traditional methods. Model parameters could also be used to construct subspectra with independent information.

ISSN:0277-3813    

DOI:10.1080/02773818908050296

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Samples of whole bark were collected from sub-alpine fir, Engelmann spruce, Douglas fir, western larch and lodgepole pine. Attempts to remove metal ions from the barks by ion exchange with dilute acid at room temperature showed that up to one third of these ions (especially calcium) are inaccessable to aqueous acid and hence not removed. The barks were subjected to vacuum pyrolysis before and after acid washing and the tars analyzed by gas chromatography as trimethylsilyl ethers. The incomplete removal of metal ions resulted in significant increase in pyrolytic production of the major products derived from polysaccharides (viz. levoglucosan and anhydroarabinose).

ISSN:0277-3813    

DOI:10.1080/02773818908050297

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Black liquor from kraft pulping of pine wood was pressure heated (about 20 MPa) for 45 minutes at both 300 °c and 350 °c and in both the presence and absence of a reducing atmosphere. Variable amounts of organic-phase (40–64 % of the black liquor organics), water-soluble (14–70 %), and volatile (12–55 %) products were formed. The organic-phase product originates mainly from the lignin fraction of black liquor, whereas, during the treatments, the corresponding hydroxy acid fraction was primarily degraded into lower acid intermediates and volatile components. The effects of temperature and gas atmosphere (carbon monoxide, hydrogen or nitrogen) on the conversion of black liquor are discussed.

ISSN:0277-3813    

DOI:10.1080/02773818908050298

出版商:Taylor & Francis Group    

年代:1989

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:10.1080/02773818908050290

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor