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Reactions of wood extractives during ECF and TCF bleaching of kraft pulp

Pulp & paper Canada, 1995-04, Vol.96 (4), p.42

Copyright Southam Business Communications, Inc. Apr 1995 ;ISSN: 0316-4004 ;EISSN: 1923-3515

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  • Title:
    Reactions of wood extractives during ECF and TCF bleaching of kraft pulp
  • Author: Jansson, M.B ; Wormald, P ; Dahlman, O
  • Subjects: BETULACEAE ; betulin ; BLANCHISSEMENT ; BLANQUEADURA ; BLEACHING ; CHEMICAL REACTIONS ; CHLORE ; CHLORINE ; chlorine free bleaching ; CLORO ; ELABORACION DE PULPA ; EXTRACTOS DE MADERA ; EXTRAIT DE BOIS ; ISOMERS ; PASTA ; PATE CELLULOSIQUE ; PULP ; Pulp bleaching ; PULPING ; REACCIONES QUIMICAS ; REACTION CHIMIQUE ; REDUCTION EN PATE ; SULFATE ; SULFATOS ; SULPHATES ; TRITERPENOIDE ; TRITERPENOIDOS ; TRITERPENOIDS ; WOOD EXTRACTS ; WOOD PULP
  • Is Part Of: Pulp & paper Canada, 1995-04, Vol.96 (4), p.42
  • Description: IN MODERN PRODUCTION of bleached kraft pulp, a large part of the lipophilic extractives originally present in the wood is removed in the kraft cooking and oxygen delignification stages, i.e., in the closed part of the mill. A minor part of the wood extractives is, however, carried over to the bleach plant with the brownstock pulp. In the bleach plant such wood extractives will, to various degrees, react with the bleaching chemicals to form oxidized and otherwise modified extractives. Figure 6 shows the sterol part of the GC-chromatograms obtained from the acetone extracts of softwood kraft pulp samples after the oxygen stage and after bleaching with chlorine dioxide to full brightness [OD(E+P)DED]. Of the original wood sterols, only the saturated sterols sitostanol and campestanol remained in the bleached pulp sample. Furthermore, six small new compounds, marked a-f, occur in the GC-chromatogram, Fig. 6. These have tentatively (from the mass spectra) been identified as oxidized sitosterol and campesterol product. Also in the ozone-treated pulp sample oxidized sterol products were found. Suggested chemical structures for some of the tentatively identified modified sterols are given in Fig. 7. Besides the sterols, fatty acids were found to be major components in all pulp extracts studied. For the fatty acids, a trend similar to that for sterols could be seen. That is, chlorine dioxide bleaching led to an almost complete reduction of the content of unsaturated fatty acids in all the pulp samples. However, the content of saturated fatty acids was only slightly lower in the bleached pulp samples than in the unbleached pulp samples.
  • Publisher: Westmount: Annex Publishing & Printing, Inc
  • Language: English
  • Identifier: ISSN: 0316-4004
    EISSN: 1923-3515
  • Source: ProQuest Central
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