Towards a new concept of lignin condensation in kraft pulping. Initial results

QC 20101004
In kraft pulping, a comparatively large amount of lignin remains in the fibres after the cook. Based on various analytical techniques for lignin, such as thioacidolysis, GPC and NMR, it is suggested that lignin condensation reactions take place during the cook. The reaction seems, however, not to involve ionic intermediates as has been suggested previously but rather a one-electron mechanism with elemental sulphur as the initiator. Support for such a reaction has been found through kraft cooks in the presence of an added phenol, 2,6-xylenol, as well as through NMR analysis of kraft lignin. It was found that the added phenol is incorporated in the pulp lignin with linkages indicative of radical coupling. Furthermore, kraft lignin was found to contain substantial amounts of chemically linked fatty acids. By complementary analyses of sulphur and polysulphide in an industrial black liquor, the presence of these compounds throughout a kraft cook was demonstrated.

TEKNIK OCH TEKNOLOGIER Materialteknik Pappers-, massa- och fiberteknik hsv//swe
ENGINEERING AND TECHNOLOGY Materials Engineering Paper, Pulp and Fiber Technology hsv//eng
Condensation
Electron transfer reactions
Fatty acids
GPC
Kraft pulping
NMR analysis
Phenols
Thioacidolysis
Cellulose and paper engineering
Cellulosa- och pappersteknik

By the author/editor: Gellerstedt, Gör ...; Majtnerová, Andr ...; Zhang, Liming

About the subject

ENGINEERING AND TECHNOLOGY: ENGINEERING AND ...; and Materials Engine ...; and Paper Pulp and F ...

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