Study on Alkali-Accessible Chromophores from Unbleached Kraft Pulp

Holzforschung ◽  
2001 ◽  
Vol 55 (5) ◽  
pp. 554-558 ◽  
Author(s):  
T. Bikova ◽  
V. Klevinska ◽  
T. Eremeeva ◽  
A. Treimanis
Keyword(s):  
Kraft Pulp ◽  
Kraft Lignin ◽  
Size Exclusion ◽  
Kraft Pulps ◽  
Black Alder ◽  
Alkaline Extract ◽  
Alkali Solutions ◽  
Exclusion Chromatography ◽  
Soluble Lignin ◽  
Cooking Conditions

Summary An approach to a chromophore composition study using the direct size-exclusion chromatography (SEC-UV) analysis of an alkaline extract of pulp fibre walls is described. Absorbance in the 290–405 nm range of 2% and 18% NaOH extract from unbleached pulps obtained by conventional and extended kraft delignification of black alder wood is compared. The effect of cooking conditions on the localisation and accessibility of chromophores is elucidated. The alkali-soluble lignin from pulp produced by extended cooking was less oxidised, less conjugated, and less coloured as compared with the conventional kraft lignin. A chromophore accessibility index is proposed. The chromogenic structures in pulps obtained by extended cooking were more resistant to alkali solutions than those in conventional kraft pulps.

Size exclusion chromatographic and UV-VIS absorption analyses of unbleached and bleached softwood kraft pulps using LiCl/1,3-dimethyl-2-imidazolidinone as a solvent

Holzforschung ◽  
2007 ◽  
Vol 61 (3) ◽  
pp. 236-241 ◽  
Author(s):  
Masahiro Yanagisawa ◽  
Akira Isogai
Keyword(s):  
Kraft Pulp ◽  
Total Yield ◽  
Degree Of Polymerization ◽  
Size Exclusion ◽  
Kraft Pulps ◽  
Residual Lignin ◽  
Light Scattering Detection ◽  
Exclusion Chromatography ◽  
Photodiode Array ◽  
Sulfite Pulp

Abstract Unbleached and bleached kraft pulps and holocellulose prepared from softwood were totally soluble in 8% LiCl/1,3-dimethyl-2-imidazolidinone (LiCl/DMI). The solutions were analyzed by size exclusion chromatography with photodiode array and multi-angle laser light scattering detection (SEC-PDA-MALLS). The mobile phase consisted of 1% LiCl/DMI. The degree of polymerization (DP) and DP distribution of the softwood kraft pulps were determined, as well as the DP distribution of residual lignins based on their UV-VIS absorption patterns. Changes in DP for kraft pulps after a conventional bleaching sequence were evaluated, and the residual lignins were analyzed in the same way. Approximately half of the residual lignin in unbleached and bleached kraft pulps was present in polysaccharide fractions with high DP, which represented approximately 90% of the total yield. Some characteristic differences in the UV-VIS absorption pattern were observed between kraft pulps bleached with oxygen and chlorine. DP, DP distribution of polysaccharides, and distribution of residual lignin were clearly different for unbleached kraft pulp, unbleached sulfite pulp, and holocellulose. An unbleached kraft pulp prepared from hardwood showed different properties to the corresponding softwood preparation. The UV-VIS absorption patterns due to residual lignins were also very characteristic for the various pulps and holocellulose.

scholarly journals Contribution of xylan to the brightness development and stability in the final ECF bleaching of eucalypt (Eucalyptus globulus Labill.) kraft pulp

Holzforschung ◽  
2013 ◽  
Vol 67 (5) ◽  
pp. 497-503 ◽  
Author(s):  
Pedro E.G. Loureiro ◽  
Joana I.T. Sousa ◽  
M. Graça. V.S. Carvalho ◽  
Dmitry V. Evtuguin
Keyword(s):  
Analytical Methods ◽  
Kraft Pulp ◽  
Resonance Raman Spectroscopy ◽  
Size Exclusion ◽  
Kraft Pulps ◽  
Vis Spectroscopy ◽  
Exclusion Chromatography ◽  
Uv Resonance Raman Spectroscopy ◽  
Modern Analytical

Abstract Xylans isolated from eucalypt kraft pulps have been characterized by modern analytical methods. The pulps were partially bleached (DEOPD) and fully bleached with either a final ClO2 (DEOPDD) or an alkaline H2O2 (DEOPDP) bleaching stage. Alternatively, xylan isolated from the DEOPD pulp was treated with ClO2 or with H2O2 under the same conditions as pulps in a final bleaching stage and were further characterized. 1H nuclear magnetic resonance, size exclusion chromatography, UV-vis spectroscopy in cadoxen solution, and UV-resonance Raman spectroscopy were applied as analytical methods. The final ClO2 stage generated new unsaturated moieties in xylan, whereas H2O2 was very effective in the removal of xylan-related chromophores. The role of xylan to the delay of brightness development in the final ClO2 stage was highlighted by means of a pretreatment with xylanase Pulpzyme HC before the final bleaching stage. By this approach, the final bleachability of the pulp was boosted and the brightness stability of the fully bleached pulp was improved.

Monitoring of Lignin and Hemicelluloses in Spent Cooking Liquor during Kraft Delignification

Holzforschung ◽  
2000 ◽  
Vol 54 (1) ◽  
pp. 66-70 ◽  
Author(s):  
T. Bikova ◽  
V. Klevinska ◽  
A. Treimanis
Keyword(s):  
Molecular Weight ◽  
Rapid Method ◽  
High Performance ◽  
Average Molecular Weight ◽  
Size Exclusion ◽  
Black Alder ◽  
Exclusion Chromatography ◽  
Glass Column ◽  
Kraft Cooking ◽  
Cooking Liquor

Summary A direct and rapid method for determining the average molecular weight (MW) and content of lignin and hemicelluloses in spent cooking liquor by high performance size-exclusion chromatography (HPSEC) using a cartridge glass column and 2.5 mM NaOH as an eluent was developed. A Uv290 detector in line with a RI detector was applied to characterise lignin and hemicelluloses, respectively, from liquor during the kraft cooking of grey and black alder wood. During the main delignification stage, the concentration of high-MW wood components in liquor changed through the maximum. The MW values of hemicelluloses in the liquor decreased to DPn = 30 ± 5 and DPw = 55 ± 5. The M̄ n and M̄ w of lignin in spent kraft cooking liquor during the main and final delignification stages did not exceed 3000 and 5000, respectively.

scholarly journals Determination of the absolute molar mass of acetylated eucalyptus kraft lignin by two types of size-exclusion chromatography combined with multi-angle laser light-scattering detectors

Holzforschung ◽  
2019 ◽  
Vol 73 (4) ◽  
pp. 363-369 ◽  
Author(s):  
Linping Wang ◽  
Yasumitsu Uraki ◽  
Keiichi Koda ◽  
Aori Gele ◽  
Xuesong Zhou ◽  
...  
Keyword(s):  
Light Scattering ◽  
Size Exclusion Chromatography ◽  
Molar Mass ◽  
Laser Light ◽  
Kraft Lignin ◽  
Laser Light Scattering ◽  
Size Exclusion ◽  
Compact Structure ◽  
Exclusion Chromatography

AbstractThe molar mass (MM) and polydispersity indices (PDI) of acetylated hardwood kraft lignin (Ac-HWKL) and Ac-HWKL fractions were measured by size-exclusion chromatography with multi-angle laser light scattering (SEC-MALLS). The detectors worked at LL658 nmand LL785 nm. The MM of Ac-HWKL measured at 785 nm was much smaller than that measured at 658 nm. The number-average (Mn) and weight-average (Mw) molar masses of Ac-HWKL determined at 785 nm were approximately 6.2 and 6.5 times larger, respectively, than the values estimated using a conventional calibration curve created with authentic polystyrene standards in tetrahydrofuran (THF). Based on the Mw of Ac-HWKL fractions, the Mark-Houwink-Sakurada equation for Ac-HWKL was established to be [η]/ml g−1=0.320 M0.24in THF and [η]/ml g−1=0.142 M0.26in dimethyl sulfoxide (DMSO). These results demonstrate that Ac-HWKL has a more compact structure in an organic solvent than polystyrene.

scholarly journals Analysis of products from the oxidation of technical lignins by oxygen and H3PMo12O40 in water and aqueous methanol by size-exclusion chromatography

Holzforschung ◽  
2010 ◽  
Vol 64 (1) ◽  
Author(s):  
Tobias Voitl ◽  
Marina V. Nagel ◽  
Philipp Rudolf von Rohr
Keyword(s):  
Size Exclusion Chromatography ◽  
Kraft Lignin ◽  
Oxidation Products ◽  
Size Exclusion ◽  
Homogeneous Catalyst ◽  
Reaction Products ◽  
Medium Ph ◽  
Acidic Solutions ◽  
Exclusion Chromatography ◽  
Technical Lignins

Abstract One kraft lignin and two lignosulfonates were oxidized in aqueous acidic solutions containing a polyoxometalate (POM). The degradations were carried out in H2O or MeOH/H2O mixtures in the presence of oxygen. The treatment with aqueous H3PMo12O40 led to the dissolution of the studied lignins in the acidic medium (pH 1–2) and to the formation of up to 6.5 wt% vanillin and 6.2 wt% methyl vanillate based on the weight of dry lignin. The lignin oxidation products were analyzed by size-exclusion chromatography (SEC). For this purpose, a SEC method was developed, which allows the analysis of kraft lignin, lignosulfonates, and reaction products thereof without the need to remove the homogeneous catalyst. This method allows the direct observation of depolymerization and repolymerization reactions and hence the provision of a tool for studying the underlying chemistry. It has been demonstrated that the depolymerization of kraft lignin in water is accompanied by counterproductive condensation reactions. These repolymerization reactions were effectively prevented by addition of methanol, which couples competitively with lignin intermediates.

Improvement of kraft pulp bleaching by treatments with laccase, urea, and refining

Holzforschung ◽  
2013 ◽  
Vol 67 (6) ◽  
pp. 651-658 ◽  
Author(s):  
Xueyu Du ◽  
Maria E. Eugenio Martín ◽  
Jiebing Li
Keyword(s):  
Lignin Content ◽  
Size Exclusion ◽  
Kraft Pulps ◽  
Pulp Bleaching ◽  
Lignin Fraction ◽  
Nuclear Magnetic Resonance Spectra ◽  
Kraft Pulp Bleaching ◽  
Mediator System ◽  
Exclusion Chromatography ◽  
Hexenuronic Acid

Abstract Unbleached Eucalyptus kraft pulps were treated by three methods and the bleaching effects have been evaluated. The treatments were performed by a laccase-mediator system (LMS), refining (R), and urea (U) alone and in combination of these methods. The bleached pulps were characterized in terms of κ number, hexenuronic acid content, brightness, and viscosity. In addition, the lignin-carbohydrate complexes (LCCs) were fractionated and characterized with regard to the fractionation yield, lignin content, and carbohydrate composition. Moreover, the 1H nuclear magnetic resonance spectra were recorded and the thioacidolysis-gas chromatography and thioacidolysis-size exclusion chromatography analyses were performed. The LMS treatment resulted mainly in a slightly better delignification as manifested by a κ number (K no.) reduction of 0.8 units. The effects of the U treatment included delignification (1.4 κ units), hexenuronic acid removal (3 μmol g-1), and improved pulp brightness (3.4 ISO units). The R treatment darkened the pulp (3 ISO units), whereas the bleaching of the R-pulp by subsequent LMS or U treatment enhanced the brightness (0.5 unit more) or delignification (0.3 unit more). The residual lignin in the pulp samples was present mainly as xylan-lignin. The Klason lignin content from the xylan-lignin fraction decreased as the degree of delignification increased. The pulp darkening followed by the R treatment was interpreted as the result of the formation of condensed lignin structures, but these condensed lignins were substantially removed by the subsequent LMS or U treatment.

Lignin-carbohydrate network in wood and pulps: A determinant for reactivity

Holzforschung ◽  
2007 ◽  
Vol 61 (6) ◽  
pp. 668-674 ◽  
Author(s):  
Gunnar Henriksson ◽  
Martin Lawoko ◽  
Maria Eugenia Eugenio Martin ◽  
Göran Gellerstedt
Keyword(s):  
Kraft Pulp ◽  
Structural Changes ◽  
Aqueous Sodium Hydroxide ◽  
Complete Recovery ◽  
Size Exclusion ◽  
Sodium Borate ◽  
Precipitation Process ◽  
Analytical Technique ◽  
Chemical Pulp ◽  
Exclusion Chromatography

Abstract Pretreatment of wood or kraft pulp with endoglucanase followed by swelling in urea leaves a non-crystalline residue that can be dissolved in strong aqueous sodium hydroxide-sodium borate solution. A stepwise precipitation process employing acid and barium ions can separate lignin-carbohydrate complexes enriched in individual polysaccharides. This procedure has been applied to eucalypt and birch wood and to the corresponding kraft pulps. Thioacidolysis of the various lignin-carbohydrate complexes was used as the major analytical technique to obtain information about the structure and structural changes in lignin. A combination of thioacidolysis and size exclusion chromatography was used to obtain knowledge on the degree of depolymerisation and repolymerisation of lignin when going from wood to chemical pulp. In contrast to spruce wood and kraft pulp, complete recovery of the lignin-carbohydrate complexes could not be obtained from hardwood samples.

Pulp delignification with oxygen and copper(II)-polyimine complexes

Holzforschung ◽  
2014 ◽  
Vol 68 (4) ◽  
pp. 377-384 ◽  
Author(s):  
Basile Gueneau ◽  
Nathalie Marlin ◽  
Alain Deronzier ◽  
Dominique Lachenal
Keyword(s):  
Redox Potential ◽  
Kraft Pulp ◽  
Oxygen Activation ◽  
Kraft Lignin ◽  
Kraft Pulps ◽  
Oxygen Delignification ◽  
Mechanical Pulp ◽  
Bleached Pulp ◽  
Carbohydrate Degradation ◽  
Unbleached Pulp

Abstract Ten Cu(II)-polyimine complexes were tested as potential catalysts in oxygen delignification of softwood kraft pulps. The ligands were chosen from the terpyridine and the phenanthroline families, including several neocuproines. One diamine-phenanthrene (daphen) was also investigated. The main purpose was to examine whether the presence of methyl or phenyl substituents would direct the oxidation toward lignin. As a catalyst for comparison, unsubstituted 1,10-phenanthroline was selected, which is known to activate both delignification and carbohydrate degradation during oxygen bleaching of kraft pulp. The variation of ligands was aiming at the complex solubility and redox potential of the parameters. The experiments were performed on a mixture of mechanical pulp and fully bleached kraft pulps, a fully bleached pulp alone, and an industrial unbleached pulp. Concerning the oxygen activation in delignification of kraft pulp, 4,7-diphenyl-1,10-phenanthroline was as good as 1,10-phenanthroline, but appeared to be more selective, which resulted in a higher DPv of cellulose after treatment. This was interpreted by the structural similarities between the ligand and the kraft lignin and by a better stability of the intermediate complex with lignin. Two Cu(II)-phenanthroline derivatives complexes (4,7- and 5,6-dimethyl-1,10-phenanthroline) were also identified as effective oxygen activators for the removal of native lignin.

Inhomogeneities in the Chemical Structure of Spruce Lignin

Holzforschung ◽  
2003 ◽  
Vol 57 (2) ◽  
pp. 165-170 ◽  
Author(s):  
H. Önnerud ◽  
G. Gellerstedt
Keyword(s):  
Chemical Structure ◽  
Kraft Pulp ◽  
Periodate Oxidation ◽  
Middle Lamella ◽  
Size Exclusion ◽  
Thermomechanical Pulp ◽  
Normal Wood ◽  
Mechanical Grinding ◽  
Spruce Wood ◽  
Exclusion Chromatography

Summary Thioacidolysis, periodate oxidation and size exclusion chromatography (SEC) were used for the analysis of spruce lignin samples. The standard thioacidolysis method was modified by including a pre-swelling of the lignocellulosic sample before the reaction, and this gave a higher yield of monomer products. Middle lamella and compression wood lignin was found to contain a larger amount of oligomers after thioacidolysis than normal wood lignin. Analysis by thioacidolysis of a thermomechanical pulp (TMP) revealed that approximately 10% of the β-O-4 structures in the lignin were cleaved due to the mechanical grinding effect. From kraft pulp, the mixture of thioacidolysis products contains a major fraction having a considerably larger molecular mass than the products from spruce wood and TMP. The structure of this material is still unknown.

Physico-Chemical Characterization of a Fractionated Kraft Lignin

Holzforschung ◽  
2000 ◽  
Vol 54 (5) ◽  
pp. 528-534 ◽  
Author(s):  
Magnus Norgren ◽  
Birger Lindström
Keyword(s):  
Molecular Weight ◽  
Chemical Characterization ◽  
Kraft Lignin ◽  
Size Exclusion ◽  
Median Surface ◽  
Self Diffusion ◽  
Exclusion Chromatography ◽  
Weighted Median ◽  
Phenolic Group ◽  
Pfg Nmr

Summary A kraft lignin was leached from a softwood pulp and fractionated by ultrafiltration. The fractions were characterized in respect to phenolic group content, molecular weight distributions and self-diffusion coefficients. The 1H-Pulsed Field Gradient (PFG) NMR self-diffusion measurements and the High-Pressure Size Exclusion Chromatography (HPSEC) analysis of the fractions, were seen to correlate fairly well. From the self-diffusion measurements, the mass-weighted median hydrodynamic radii of the diffusants in the fractions, were calculated assuming spherical fragments. Furthermore, the content of phenolic groups in the fractions, was found to decrease by increasing hydrodynamic radius and molecular weight, but the calculated median surface charge densities of the macromolecules, were determined to be constant in the range of oligomers up to at least 65 structural units.

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