摘要:

An acid-washed, oxygen-delignified, softwood kraft pulp was delignified with peracetic acid (Pa) at initial pH 2.5, 4.8 and 7.0. The inclusion of 5 ppm on pulp of Mn2+, Fe3+, Cu2+, V5+, or Co2+caused wasteful decomposition of Pa while Ni2+had no effect. None of the cations caused a significant decrease in kappa number while Co2+at all pHs and Fe3+at pH 2.5 resulted in lower viscosities.

ISSN:0277-3813    

DOI:10.1080/02773819809349580

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

When used in pulp bleaching, peracetic acid is consumed by two competitive pathways: oxidation of pulp and wasteful reactions such as decomposition. In this paper, the peracetic acid consumed in wasteful reactions is quantified by determining the gaseous products evolved. It is found that although carbon dioxide is formed under certain conditions, oxygen is the dominant product of the wasteful reactions. The oxygen formation is directly proportional to the consumption of oxidants (as peracetic acid and hydrogen peroxide) in the wasteful reactions with 2 moles of oxidant consumed per mole of oxygen formed. Therefore, the brightening efficiency during peracetic acid treatment can be characterized by correcting the measured peracetic acid consumption for decomposition. The peracetic acid brightening results for an oxygen delignified softwood kraft pulp are reported. It is found that a significant amount of peracetic acid is consumed by the wasteful reactions during the brightening. The effect of process parameters on the peracetic acid brightening efficiency is determined. It is shown for an oxygen delignified softwood kraft pulp that there is a unique relationship between pulp brightness gain and peracetic acid consumption due to the pulp oxidation irrespective of the brightening conditions.

ISSN:0277-3813    

DOI:10.1080/02773819809349581

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The topochemistry of thiol-photostabilization of hardwood BCTMP (bleached chemithermomechanical pulp) was investigated by scanning electron microscopy (SEM). Employing advanced SEM methods, the location of unextractable sulfur across the fiber wall was determined for post-photolyzed BCTMP fibers. These studies illustrate that thio additives remove chromophores across the fiber wall.

ISSN:0277-3813    

DOI:10.1080/02773819809349582

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The kinetics of the pyridine-catalyzed reaction of succinic anhydride (SA) and octenyl succinic anhydride (OSA) with Scots pine (Pinus sylvestris) have been investigated, and activation energies determined. The activation energies for surface reactions between wood and SA or OSA were determined as 79.5 (±13.0) and 29.6 (± 4.6) kJ/mol respectively. The low value of the latter activation energy, suggests that hydrogen bond breaking is a rate determining step with the reaction of OSA with wood. With SA the activation energy is of a similar magnitude to literature values for anhydride-alcohol reactions. The kinetics of reaction over extended time was analysed to see if diffusion dominated the process, complex profiles were observed which were not amenable to simple analysis.

ISSN:0277-3813    

DOI:10.1080/02773819809349583

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Abaca fibre was treated with 1, 2.5, and 5% sodium hydroxide at 25, 35, and 50° C for 0.5-5 h. The dissolved alkali lignins LA were separated from the solubilized polysaccharides using a two step precipitation method. The chemical and structural compositions of the pure lignin fractions LA were determined by UV, GPC, FT-IR,13C-NMR spectroscopy and nitrobenzene oxidation. All of the lignin fractions LA are free of associated polysaccharides. Their molecular-average weights ranged from 1960 to 2640. The results obtained by alkaline nitrobenzene oxidation showed that all the lignin fractions LA contain large amounts of non-condensed syringyl units, together with fewer non-condensed guaiacyl and p-hydroxyphenyl units. β-O-4 and β-5 ether bonds are found to be the major linkages between the lignin structural units. The less common β-β, β-5, and 5-5' carbon-carbon linkages are also identified to be present between the lignin structural units. p-Coumaric acid and ferulic acid are linked to lignin molecules by ester and ether bonds, respectively.

ISSN:0277-3813    

DOI:10.1080/02773819809349584

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An improvement in the peroxyformic acid process for the production of chemical pulps fromEucalyptus grandiswood chips and sugar cane bagasse is described. The pulping of these lignocellulosics was carried out in a single stage at 75°C (3 h) in order to benefit from the action of the peroxyformic acid and a subsequent formic acid reflux (110°C, 2 h), using the same liquor. Efficient distillation of the spent liquor allowed recovery of a large quantity of formic acid and phenolic lignin, the latter obtained after mild saponification, followed by precipitation in acidic media. The pulping process was completed with a 0.25M NaOH extraction of the pulp at 60°C to dissolve more lignin. Good quality unbleached pulps were obtained. Kappa numbers (KN) of 14 and 13, and intrinsic viscosities [n] of 1130 and 980 dm3. Kg−2were obtained, respectively, forE. grandisand sugar cane bagasse. The structures of the lignin fractions were studied by size exclusion chromatography; methoxyl content analysis; elemental analysis; UV; IR; and1H,13C, and31P NMR, The lignins were found to undergo demethylation, condensation, ring opening, formylation of hydroxyl groups, and aryl-alkyl ether cleavage during pulping.

ISSN:0277-3813    

DOI:10.1080/02773819809349585

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The feasibility of using FT-Raman spectroscopy for rapid determination of wood basic density was examined for twoEucalyptusspecies, including samples of various ages and colors, which are of importance as a plantation source. Wood basic density is an important indicator of wood physical properties, pulp properties and pulpwood productivity. Measurement included basic density (BD), extractives-free (EF) BD, alkali-extractives-free (AF) BD, total-extractives-free (TF) BD and extraneous compounds-free (ECF) BD were measured. The application of 2nd derivatives transformation to Raman spectroscopic data revealed highly significant correlations between measured and Raman predicted values for BD, EF-BD, AF-BD, TF-BD and ECF-BD with standard error of prediction (SEP) ≒ 8, 45, 22, 37 and 49 kg/m3in the calibration (for known samples) and SEP ≒ 28, 38, 40, 29 and 40 kg/m3in the prediction (for unknown samples), respectively. Consequently, this method has proved its validity for analyzingEucalyptusnative wood meal samples, regardless of their age and color, to determine basic density. FT-Raman spectroscopy can be used for (1) the measurement of physical properties of forest products, and (2) elite tree selection to improve both quality and productivity, reducing the cost of pulp and paper products and our reliance on natural forests.

ISSN:0277-3813    

DOI:10.1080/02773819809349586

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor