Purification of cellulosic pulp by hot water extraction

Marc Borrega (Corresponding Author), Herbert Sixta

Research output: Contribution to journalArticleScientificpeer-review

26 Citations (Scopus)


Hot water extraction (HWE) of pulp in a flow-through reactor was evaluated as a method to purify paper-grade pulps. About 50-80 % of the xylan and up to 50 % of the lignin in unbleached birch Kraft pulp was extracted by the HWE without losses in cellulose yield. The residual xylan content in the extracted pulps was predominantly too high for dissolving-grade applications, but some of the pulps with a xylan content of 5-7 % might still be suitable as rayon-grade pulps. Increasing extraction temperature lowered the xylan content at which cellulose yield started to decrease. Furthermore, at any given xylan content, increasing extraction temperature resulted in cellulosic pulp with higher degree of polymerization. The extracted xylan was recovered almost quantitatively as xylo-oligosaccharides. The results suggest that HWEs at elevated temperatures may be applied to purify cellulosic pulps, preferably containing a low xylan content, and to recover the extracted sugars.

Original languageEnglish
Pages (from-to)2803-2812
Number of pages10
Issue number6
Publication statusPublished - Dec 2013
MoE publication typeA1 Journal article-refereed


  • Birch kraft pulp
  • Cellulose
  • Dissolving-grade pulp
  • Hot water extraction
  • Xylan


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