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December 17, 2015
Benoît Arnoul-Jarriault, LGP2's Ph.D. student, defended his doctoral thesis: "Hemicellulose extraction of paper grade pulp for dissolving pulp production".
This Grenoble Alpes University doctoral thesis was prepared under the supervision of Dominique Lachenal, Professor, and of Christine Chirat, Associate Professor (Grenoble INP-Pagora / LGP2).
Dissolving pulps, which are composed of 95% cellulose, are the raw materials for the production of regenerated cellulose fibers for textile application and for the production of cellulose derivatives. These products are alternatives to oil based materials. A growing demand in such products is expected in the next decades. Therefore, additional capacities in the production of wood dissolving pulp must be created.
The purpose of this work is to develop hemicellulose removal processes with the aim to convert a softwood kraft paper pulp into a dissolving pulp. Three extraction methods were tested: A cold caustic extraction process (CCE) performed under conventional and unconventional conditions; A process consisting in an acid stage at high temperature (up to 150°C) followed by a hot caustic extraction (A-HCE); An enzymatic hydrolysis using xylanase, mannanase, and cellulase.
Conversion was quite successful with the two first processes. However, 100% of hemicellulose removal was never reached. In order to improve the hemicellulose extraction efficiency, several pre-treatments were tested (refining, steam explosion, TEMPO oxidation). The addition of a refining stage allowed for a reduction of the NaOH concentration during CCE extraction without affecting the hemicellulose extraction efficiency.
The last part of this thesis work focused on the dissolving pulp swelling. A new and rapid test for the characterization of fiber swelling was developed. This method was used as an approach to the assessment of dissolving pulp reactivity in the viscose process in place of the Fock's method.