摘要:

Pretreatment of softwood chips with Na2S liquors at moderately-elevated temperatures prior to a kraft stage delignification resulted in higher pulp viscosity at a given kappa number as compared to that of a conventionally-cooked reference kraft pulp. Final pulp yields were equivalent to, or slightly better than for conventional kraft pulps. The high viscosity is due to the lower alkali requirement during the kraft stage as a result of the pretreatment. The decreased alkali requirement is due to the extraction and removal of hemicelluloses during pretreatment which normally produce sugar acids via peeling reactions. The presence of sulfide in the pretreatment promotes lignin degradation and also enhances polysaccharide stability during the subsequent kraft stage. When kraft pulps, pretreated with sulfide-contaim'ng liquors, were further delignified in an oxygen stage, lower kappa numbers at equivalent viscosity were obtained versus conventional kraft-0? treatment. This enhanced polysaccharide stability toward an oxygen stage can also be achieved by treating a conventional kraft pulp with sulfide-containing liquors, including green liquor and black liquor, but a lesser effect is achieved compared with chip pretreatment.

ISSN:0277-3813    

DOI:10.1080/02773818508085205

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Loss of brightness in mechanical pulp as a result of storage time of Western Hemlock chips has been correlated with a decline in d-catechin in the chips. Oxidative polymerization of the d-catechin to an insoluble polymer containing catechol groups is suggested as the cause of the brightness loss.

ISSN:0277-3813    

DOI:10.1080/02773818508085206

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Despite continuing interest in various processes for producing ethanol or other chemicals from agricultural and wood residues, little attention has been given to improving the kinetic modeling of dilute acid saccharification of cellulosics, a key step in many of these processes. A new model for cellulose saccharification is proposed. It incorporates the effect of the neutralizing capacity of the substrate, the presence of readily hydrolyzable cellulose, and the reversion reactions of glucose. Although general in nature, the model was developed specifically for application to the dilute sulfuric acid saccharification of prehydrolyzed wood lignocellulose. A computer program to simulate the new model under various reaction conditions was prepared. This program reasonably predicts yields of fermentable (monomeric) sugar, reducing sugar, reversion material, remaining cellulose, as well as glucose lost by dehydration, all as a function of acid concentration, temperature, and reaction time.

ISSN:0277-3813    

DOI:10.1080/02773818508085207

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Studies are reported on the chemical nature and mechanism of formation of the components of the oil fraction obtained by the alkali-catalyzed liquefaction of aspen poplar wood and separately of cellulose. Along with the smaller molecular weight compounds reported earlier (5) evidence has been obtained for the presence of polymeric fractions involving ether linkages and which show a bimodal pattern of molecular weights. Using appropriate model substances, some evidence ha3 been obtained for the production and involvement of one- and two-carbon fragments as well as ketene-type intermediates in the liquefaction process. Examination of the role of pH during the conversion process suggests that the initially alkaline medium is required to degrade the cellulose to smaller fragments, including possible saccharinic acids, with a corresponding decrease in pH. Then at an appropriate pH (now acidic) and temperature the resulting degradation products are converted to components of the final oil.

ISSN:0277-3813    

DOI:10.1080/02773818508085208

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The lignins extractable by acetone from Eucalyptus regnans wood after steam explosion treatment by either the Canadian Iotech Process1or the Australian Siropulper Process2have been examined by13c NMR spectroscopy. Comparison with MWL showed structural changes which are discussed, compared for the two processes and compared with those for another hardwood (aspen) and a softwood (Pinus radiata). IR, MW and elemental analysis data are also discussed.

ISSN:0277-3813    

DOI:10.1080/02773818508085209

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Changes in the composition of gum rosin during disproportionate in the presence of 5% palladium-on-charcoal have been determined by gas chromatography. The principal reaction product was dehydro-abietic acid. The exocyclic vinyl group of the pimaric/isopimaric-type resin acids was hydrogenated completely. Only a small amount of dihydroabietic acids was formed. Eight dihydro resin acids were identified. No tetrahydro resin acids were observed.

ISSN:0277-3813    

DOI:10.1080/02773818508085210

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Dynamic thermogravimetry (tga), differential thermogravimetry (dtg), and Fourier Transform-Infrared Spectroscopy (FT-IR) were performed on a variety of celluloses with different cyr3tallinities. The data were compared to the crystallinlty indices (C.I.) determined by X-ray diffraction. Highly significant correlations (99.9%) included: a positive linear correlation of the maximum dtg value; a logarithmic relation of the temperature at which the initial 10% weight loss occurred; and a linear relationship of three FT-IR absorbance ratios (1108/1091 cm−1), (1430/1403 cm−1), and (1459/1403 cm−1). A significant logarithmic correlation was also found for the temperature at maximum dtg for cotton linter samples. These relationships are discussed.

ISSN:0277-3813    

DOI:10.1080/02773818508085211

出版商:Taylor & Francis Group    

年代:1985

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:10.1080/02773818508085204

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor