Extraction of hemicelluloses after chemical pretreatment combined with mild steam explosion
2011 (English)In: 16th International Symposium on Wood, Fiber and Pulping Chemistry - Proceedings, 2011, 867-871 p.Conference paper (Refereed)
The aim of this research is to separate different wood components from softwood as a first step towards development of novel materials made from Scandinavian wood. The approach is pre-treatment with a reducing agent in combination with mild steam explosion (T< 160°C, t < 15 min); followed by extraction with different liquors. The aim is to retain an increased amount of hemicelluloses in general, and glucomannans in particular, during chemical treatments, preferably of high molecular weight. Experiments were performed on wood chips from spruce in small scale steam explosion equipment. A pre-treatment method with sodium borohydride (NaBH 4) as a reducing agent model substance was chosen. Wood chips pre-treated with NaBH 4 were compared to untreated chips, and the chips were treated with steam explosion followed by extraction in alkali. Results showed that a higher amount of glucomannan was retained in chips treated with NaBH 4 than in untreated chips. An increase in the extraction rate as an effect of steam explosion indicates a possible combination of chemical reactions that breaks up the lignin-polysaccharide network and a more porous wood structure. An experimental series with wood powder as raw material were also performed in order to study the chemical reactions during steam explosion, e. g. autohydrolysis. Water impregnated wood powder as well as wood powder treated with NaBH 4 was subjected to mild steam explosion for different retention times. It was shown that a decrease in hemicelluloses content occurred after only 5 min, and the degradation was more severe at longer residence times. However, the degradation of hemicelluloses was not as severe as in the chemical treatments at conditions corresponding to chemical pulping, and consequently might be a more prudent method to access the wood structure. Extractions after steam explosion were investigated at different pH levels, and the results showed that most of the glucomannan was still in the wood residue at the tested conditions. The stabilization of glucomannans by pre-treatment with NaBH 4 was clearly seen also in these experiments.
Place, publisher, year, edition, pages
2011. 867-871 p.
(galacto)glucomannan, Mild steam explosion, NaBH 4, Wood component separation, Agent model, Autohydrolysis, Chemical pre-treatment, Chemical treatments, Extraction rate, Glucomannan, High molecular weight, In-chip, NaBH 4
, Novel materials, PH levels, Pre-Treatment, Pretreatment methods, Residence time, Retention time, Small scale, Sodium borohydrides, Steam explosion, Wood chip, Wood components, Wood powder, Wood residues, Wood structure, Cellulose, Experiments, Explosions, Explosives, Separation, Sodium, Steam, Wood products, Wooden buildings, Wooden construction, Degradation, Explosion, Extraction, Glucomannans, Hemicelluloses, Prehydrolysis, Pretreatment, Softwoods
Paper, Pulp and Fiber Technology
IdentifiersURN: urn:nbn:se:kth:diva-149926ScopusID: 2-s2.0-84855646444OAI: oai:DiVA.org:kth-149926DiVA: diva2:741865
16th International Symposium on Wood, Fiber and Pulping Chemistry, ISWFPC, 8 June 2011 through 10 June 2011, Tianjin
QC 201408292014-08-292014-08-282014-08-29Bibliographically approved