摘要:

Black spruce sawdust, when treated batchwise, in accordance with the principles of the gel degradation theory, with dioxane: H2O:HCl (90:8:1.8 by volume) at various extents of lignin solubilization, gave a series of lignin fractions. The undialyzed lignin preparations, characterized by Klason lignin, methoxy contents, microanalysis, and U.V. absorptivity, were found to be reasonably uniform in composition. Gel permeation chromatography with a combination of refractive index (RI) and Low Angle Laser Light Scattering (LALLS) detection gave fractions that qualitatively resembled those obtained by the degradation of synthetic model polymer gels. In efforts to quantitatively correlate molecular weights (Mw) of these lignins with the existing gel degradation models, however, the problems of lignin fluorescence, association and recondensation were encountered. During the batchwise dioxane:H2O:HCl extraction of wood, irreversible recondensation of the lignin fragments took place, limiting analysis of the results in the context of the gel degradation theory, revealing however, a salient feature of delignification.

ISSN:0277-3813    

DOI:10.1080/02773818708085249

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Recent results of Whiting and Goring on the acid-sulphite pulping of Isolated middle-lamella and secondary-wall tissues of spruce wood have permitted a aw theoretical analysis of the topo-chemistry of delignification. Unlike the previous data obtained by U.V. microscopy of thin wood sections, the new results did not require the postulation of a different reaction rate constant in each morphological region. By assuming only that the crosslink density of the secondary wall was about 0.75 of that of the middle lamella, gel degradation theory provided a good fit to the experimental points. This analysis suggests that the topochemical effect observed in acid-sulphite pulping is determined solely by lignin chemistry. The contrast in the conclusions derived from the two sets of data leads to consideration of which of the data sets is more representative of the topochemistry in the pulping of Intact wood.

ISSN:0277-3813    

DOI:10.1080/02773818708085250

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The technique of photoacoustic Fourier transform infrared spectroscopy (FTIR-PAS) was applied to the study of mechanical pulp brightening with hydrogen peroxide. Intensities relative to three internal standard peaks (3400, 1510 and 1056 cm−1) were used since the absolute photoacoustic signal intensities were not reproducible. The internal standard method yielded a reproducibility of better than 5Z and made it possible to observe significant changes in the 1750–1600 cm−1region upon brightening with peroxide. The peak intensities were found to decrease due to alkaline deacetylation (1740 cm−1), and to the net removal of conjugated carbonyl structures (1650 cm−1).

ISSN:0277-3813    

DOI:10.1080/02773818708085251

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Bleached kraft effluent (BKE) is highly coloured due to the presence of high molecular weight, chlorinated, oxidised lignin. The dimethyl formamide-soluble portion of BKE was radiolabelled by methoxylation with14C-methyl iodide, and the resulting product (C14-BKE) was used to Investigate the mechanism of colour removal by fungi and bacteria. The white-rot fungiCoriolus versicolorandPleurotus sajor-cajudecolorised the solutions, and depolymerised the C14-BKE. Both fungi produced about 16Z14CO2from C14-BKE In 20 days. The three bacteria tested,Bacilluscereus and two strains ofPseudomonas aeruginosa, removed colour primarily by adsorption with little depolymerisation or mineralization. The adsorbed C14-BKE could be removed from bacterial cells by washing with 0.1 M NaOH.

ISSN:0277-3813    

DOI:10.1080/02773818708085252

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Kraft lignins have been isolated from the black liquors obtained a) after normal kraft cooking of pine wood to different yield levels and b) after a flow-through cook. After purification, the two series of lignins have been subjected to oxidative degradation in a four step reaction sequence leading to the formation of substituted aromatic carboxylic acid Methyl esters. The yields and distribution of the different esters obtained from the flow-through cook indicate that in kraft cooking the lignin which goes into solution undergoes structural changes which coincide with the transition points between the initial, the bulk and the final delignification phases. From the other series of cooks, changes in the frequency of occurrence of the individual esters were also observed as the cook proceeded. These changes could not, however, be attributed to the different phases of delignification but took place rather continuously during the cook. The observed results are discussed with reference to known features of delignification chemistry in kraft cooking.

ISSN:0277-3813    

DOI:10.1080/02773818708085253

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Residual lignins in an unbleached and a semibleached softwood (Pinus taedaL.) kraft pulp were isolated by enzymatic hydrolysis of polysaccharides in the pulps. After purification, the residual lignins were characterized. A dissolved lignin was also isolated from the alkaline extraction spent liquor by acidification and characterized.

ISSN:0277-3813    

DOI:10.1080/02773818708085254

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A lignin model (3E) with a propanol group on the β-carbon has been heated In alkali with no additives and with NaSH and anthrahydroquinone (AHQ) additives. The β-aryl ether bond of the model is efficiently fragmented by AHQ, but not by NaSH or simple NaOH. A competing cyclization of the propanol group with the quinonemethide of the model interferes with NaOH and NaSH fragmentation reactions. The data suggest that AHQ reacts by way of a mechanism different from that of NaSH - the AHQ by an electron transfer mechanism and the NaSH by an adduct mechanism. The reactions of β-allyl (3D) and β-propyl trityloxy (3F) models were also performed. The fragmentation efficiencies In these cases ware: AHQ > NaSH > NaOH.

ISSN:0277-3813    

DOI:10.1080/02773818708085255

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A brief overview of Raman spectroscopy and the photon scattering phenomena which underly it is presented, together with the rationale for applying the methodology to the study of lignocellulosics. The sequence of studies undertaken at The Institute of Paper Chemistry to apply the methods to investigation of celluloses, chemical pulps, wood and high yield fibers are then reviewed.

ISSN:0277-3813    

DOI:10.1080/02773818708085256

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0277-3813    

DOI:10.1080/02773818708085248

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor