Jorma Sundquist

Proposed mechanism of the enzymatic bleaching of kraft pulp with xylanases

The modification of fibre surface by an enzymatic pretreatment was studied by analyzing the hydrolysis products released from the pulps and the molar mass distribution of the alkali-extracted residual lignin. In kraft pulp, the reprecipitated or readsorbed alkali-resistant xylan appears to form a physical barrier to the extraction of residual lignin from the fibres. The treatment of kraft pulp with hemicellulases removes some of this xylan and renders the fibre structure more permeable. The increased permeability allows the passage of lignin or lignin-carbohydrate molecules in higher amounts and of higher molecular masses in the subsequent chemical extraction. The improved extractability of lignin leads to higher brightness of pulp, or can alternatively be exploited to reduce the consumption of bleaching chemicals.

13C CPMAS NMR investigations of cellulose polymorphs in different pulps

In order to obtain information about the crystallinity and polymorphs of cellulose, and the occurrence of hemicelluloses in pulp fibers, wood cellulose, bacterial cellulose, cotton linters, viscose, and celluloses in different pulps were investigated by solid state 13C CPMAS NMR spectroscopy. A mixed softwood kraft pulp and a dissolving-grade pulp were treated under strongly alkaline and acidic conditions and the effect on cellulose crystallinity was studied. The presence of different crystalline polymorphs of cellulose and the amounts of hemicelluloses are considered.

Characterization of Alkali Soluble Fraction of Steam Exploded Birch Wood

Birch wood chips, with or without peroxyacetic acid pretreatment, were subjected to steam explosion treatment at 160, 220 and 250°C for different periods of time to reach the same severity or P-factor values (1000, 15,000 and 96,000 min) at each temperature. The exploded pulp was subsequently extracted with water and a 0.4% alkali solution. The alkali soluble fraction was studied by means of elemental, methoxyl analysis, conductometric titration, 1 H-, quantitative 13 C-NMR and FTIR spectroscopy, and gel permeation chromatography methods. With an increasing P-factor value, the polysaccharide content of the alkali soluble fraction decreases rapidly, the syringylpropane unit and aliphatic OH-group concentration decreases, the phenolic OH-group concentration increases, lignin side chains are subjected to oxidation and partial destruction, and pseudolignin is incorporated into lignin macromolecules. The increase in temperature at equal severity of steam explosion has some effect on the removal of the syringylpropane units and on pseudolignin formation. Peroxyacetic acid pretreatment does not have a pronounced effect on the structure of alkali soluble compounds

Formic acid/peroxyformic acid pulping. IV, Lignins isolated from spent liquors of three-stage peroxyformic acid pulping

On etudie les structures et proprietes des lignines dissoutes lors des differentes etapes de la mise en pâte des bois de bouleau, pin et epicea par les acides formique et peroxyformique

THE INVESTIGATION OF CELLULOSE POLYMORPHS IN DIFFERENT PULPS USING 13C CPMAS NMR

ABSTRACT In order to obtain information about the crystallinity and polymorphs of cellulose and the occurrence of hemicelluloses in pulp fibers, wood cellulose, bacterial cellulose, cotton linter, viscose and celluloses in different pulps were investigated by solid state 13C CPMAS NMR spectroscopy. A mixed softwood kraft pulp and a dissolving pulp were treated under strongly alkaline and acidic conditions and the effect on the cellulose crystallinity was studied. The presence of different crystalline polymorphs of cellulose and the amount of hemicelluloses are considered.