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Abstract
This study evaluated the solubility of low-processed wood fibers produced from a low temperature acid hydrotropic fractionation (AHF) in an ionic liquid (IL) 1,5-diazabicyclo[4.3.0]non-5-enium acetate (DBNH[OAc]. Unbleached wood fibers produced from AHF using
p-Toluenesulfonic acid (
p-TsOH) with or without post-treatments with lignin and hemicelluloses content up to 15% and 25%, respectively, were dissolved directly into the ILDBNH[OAc]. Post-AHF treatments using dilute alkaline and glycerol swelled the cellulose and partially removed residual lignin resulting in improved dissolution. Semi-quantitative 2D HSQC NMR analyses revealed that the undissolved wood fiber residues were enriched with G units and condensed S units (S
cond), demonstrating, as expected, that G units and condensed lignin substructures have a negative effect on dissolution in DBNH [OAc]. Therefore, AHF with rapid fractionation at low temperatures offers a promising advantage over existing high temperature pulp dissolving fiber(PDF) processes in terms of reducing energy input, lowering lignin content as well as reducing lignin condensation for producing man-made cellulosicfibers (MMCF).
Citation
Wang, Huihui; Hirth, Kolby; Zhu, Junjun; Ma, Qianli; Liu, Chuanfu; Zhu, J.Y. 2019. Dissolution of less-processed wood fibers without bleaching in an ionic liquid: effect of lignin condensation on wood component dissolution. International Journal of Biological Macromolecules. 134: 740-748.