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Highly bleachable wood fibers containing less condensed lignin from acid hydrotropic fractionation (AHF)Author(s): Qingzhi Ma; Kolby Hirth; Huamin Zhai; J.Y. Zhu
Source: ACS Sustainable Chemistry & Engineering. 8(24): 9046-9057.
Publication Series: Scientific Journal (JRNL)
Station: Forest Products Laboratory
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DescriptionThis study evaluated the bleachability of wood fibers from acid hydrotropic fractionation (AHF) of birch using ptoluenesulfonic acid (p-TsOH) at low temperatures below 90 °C. The wood fibers had varying amounts of lignin after AHF under different conditions using both batch and flow-through configurations. The extent of lignin reprecipitation in batch mode was evaluated by extended washing with p-TsOH. 2D 13C−1H nuclear magnetic resonance (NMR) spectroscopy indicated that residual lignin on fibers from batch reaction was significantly more condensed than that from flow-through under equivalent conditions. Furthermore, condensation substantially affected oxidative bleaching by reducing the reactivity of the residual lignin. Even a little variation in the extent of lignin condensation showed a marked effect on sample bleachability. Specifically, oxygen bleaching at 110 °C removed 79% of residue lignin from a batch fractionated fiber sample with 7% β-O-4 aryl ether linkage and resulted in 55% ISO fiber brightness. The same oxygen bleaching removed 87% of residue lignin from a flow-through fractionated fiber sample with almost the same lignin content but with a higher β-O-4 of 16%, or lower degree of lignin condensation, and higher brightness of 59% ISO. The 4% increase in brightness with the same loading of bleaching chemical translates to significant cost reduction. Furthermore, a brightness of 70% or more can be achieved with single stage peroxide bleaching for the flow-through AHF fibers
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CitationMa, Qingzhi; Hirth, Kolby; Zhai, Huamin; Zhu, J.Y. 2020. Highly bleachable wood fibers containing less condensed lignin from acid hydrotropic fractionation (AHF). ACS Sustainable Chemistry & Engineering. 8(24): 9046-9057.
Keywordsacid hydroytrope fractionation, fiber bleaching, lignin condensation, NMR lignin analyses
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