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Title:
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Characteristics of Wheat Straw Lignins from Ethanol based Organosolv Treatment
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Author(s):
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Huijgen, W.J.J.; Telysheva, G.; Arshanitsa, A.; Gosselink, R.J.A.; Wild, P.J. de
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Published by:
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Publication date:
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ECN
Biomass & Energy Efficiency
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27-5-2014
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ECN report number:
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Document type:
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ECN-W--13-032
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Article (scientific)
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Number of pages:
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13
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Published in: Industrial Crops and Products (Elsevier), , 2014, Vol.59, p.85-95.
Abstract:
tNon-purified lignins resulting from ethanol-based organosolv fractionation of wheat straw were char-acterized for the presence of impurities (carbohydrates and ash), functional groups (hydroxyl, carboxyland methoxyl), phenyl-propanoid structural moieties, molar mass distribution and thermal behavior. Inaccordance with its herbaceous nature, the syringyl/guaiacyl-ratio of the wheat straw lignins was sub-stantially lower than of Alcell lignin. In addition, the content of p-hydroxyphenyl and carboxyl groups issubstantially higher for the wheat straw lignins. The non-purified organosolv lignins had a high puritywith 0.4–5.2% carbohydrate impurities, both originating from lignin to carbohydrate complexes and resid-ual organosolv liquor. The use of H2SO4in the organosolv process improved the lignin yield, but at lowacid doses increased the carbohydrate impurities. For applications where a low amount of carbohydratesis important, lignin from a high-temperature autocatalytic organosolv process was found to be pre-ferred. The highest content of total hydroxyl groups was determined when lignins were produced using30 mM H2SO4as catalyst or 50% w/w aqueous ethanol as solvent for the organosolv process. Aliphatichydroxyl groups, the most predominant type of hydroxyl groups present originating for a substantial partfrom residual carbohydrates, were found to decrease with reaction time and ethanol proportion of theorganosolv solvent. The correlations between organosolv process conditions and lignin characteristicsdetermined can facilitate the use of organosolv lignins in value-added applications such as in polymersand resins and as a feedstock for bio-based aromatics.
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