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Ron Janzon Jürgen Puls Andreas Bohn Antje Potthast Bodo Saake 《Cellulose (London, England)》2008,15(5):739-750
Different paper grade pulps were extracted with nitren in order to produce dissolving pulps and polymeric xylan. The yield
and molecular structure of the extracted pulps were investigated by carbohydrate analysis and HPSEC combined with fluorescence
labelling in order to additionally monitor the carbonyl and carboxyl group profiles of the pulps. The supramolecular structure
of selected pulps were further studied by solid state 13C-CP/MAS-NMR and wide-angle X-ray scattering (WAXS). These supramolecular data of nitren extracted pulps were compared to
samples extracted with NaOH and a conventional dissolving pulp in order to classify the properties of nitren extracted pulps.
Nitren extraction results in selective xylan removal without noticeable degradation or oxidation of the cellulose fraction.
The resulting dissolving pulps have high molar masses, a narrow molar mass distribution and the typical contents of carbonyl
and carboxyl groups. The supramolecular structure of cellulose is less affected by nitren compared to strong NaOH, and the
resultant dissolving pulps still have the cellulose I structure.
All laboratories are members of the European polysaccharide network of excellence EPNOE. 相似文献
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Different paper-grade pulps were extracted with nitren, NaOH and KOH in order to produce dissolving pulps and polymeric xylan.
The yield and structure of the isolated nitren and alkali xylans were investigated by carbohydrate analysis, HPSEC and 1H-NMR spectroscopy. In addition the effect of washing stages on the residual nickel content of the nitren xylans was investigated.
By nitren extraction up to 98% of the xylan could be extracted out of the fully bleached eucalyptus and birch kraft pulps.
The nitren extracted kraft xylans had DP values between 95 (birch) and 111 (eucalyptus). At most 5 mol% of the xylose units
were substituted. In the case of pulps with low mannan content only marginally differences between the nitren and alkaline
(KOH, NaOH) extractions occurred. The extraction of the relatively “mannnan rich” pulps of this study like softwood kraft
and beech sulfite pulps revealed that the dissolution effect regarding mannans increased in the following order: nitren < KOH < NaOH.
In general the nitren extractions required a lower chemical charge compared to the alkaline extractions, in order to yield
similar amounts of xylans. On the other side the necessity of an effective nickel removal is a disadvantage of the nitren
extractions. 相似文献
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