Behavior of Eucalyptus Wood Xylans across Kraft Cooking |
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Authors: | Andréia S Magaton Jorge L Colodette Dorila Piló-Veloso José L Gomide |
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Affiliation: | 1. Department of Chemistry , Universidade Federal de Minas Gerais , Belo Horizonte, Brazil;2. Department of Forest Engineering , Universidade Federal de Vi?osa , Vi?osa, Brazil |
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Abstract: | Abstract The 4-O-methylglucuronoxylans isolated from wood, pulp, and black liquor from six eucalyptus wood species were characterized. The 1H nuclear magnetic resonance (NMR) studies revealed that all eucalyptus wood xylans contain O-2-substituted 4-O-methylglucuronic acid (MeGlcA) groups with hexose residues (9–26%). Their molecular weight (Mw) and polydispersity varied in the range of 26,083–28,405 g.mol?1 and 1.13–1.17, respectively. The xylan retention during pulping increased with increasing degree of MeGlcA substitution in the xylose ring. An average of 54% xylans was retained in the pulp and the remaining 46% were degraded and/or dissolved in the black liquor (39% degraded and 7% dissolved). The average Mw of the xylans retained in the pulp and dissolved in the black liquor is influenced by pulp kappa number and averaged 20,134 and 14,778 g.mol?1, respectively, at kappa 17. The average substitution degree of uronic acids, including MeGlcA and hexenuronic acids (HexA) in the xylans isolated from pulps (kappa 17) and black liquors were 1.05 and 1.13/10 xyloses, respectively. Of the total uronic acids present in the six original woods, an average of 36% w/w was retained in the pulps. |
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Keywords: | Eucalyptus xylans 4-O-methylglucuronic acids kraft pulps black liquor methanolysis-GC NMR spectroscopy size exclusion chromatography |
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