EXTRACTION OF HEMI-CELLULOSES AFTER CHEMICAL PRETREATMENT COMBINED WITH MILD STEAM EXPLOSION
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 (NaBH4) as a reducing agent model substance was chosen. Wood chips pre-treated with NaBH4 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 NaBH4 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 NaBH4 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 NaBH4 was clearly seen also in these experiments.
mild steam explosion wood component separation (Galacto)glucomannan NaBH4
Kerstin Jedvert Anna Saltberg Mikael E.Lindstr(o)m Hans Theliander
Department of Forest Products and Chemical Engineering, Chalmers University of Technology,SE-412 96 Department of Wood Chemistry and Pulp Technology,Royal Institute of Technology, SE-100 44 Stockholm,
国际会议
16th International Symposium on Wood,Fiber and Pulping Chemistry(第十六届木材、纤维及制浆化学国际会议)
天津
英文
867-871
2011-06-08（万方平台首次上网日期，不代表论文的发表时间）