A note on the chemical fate of the DABCO catalyst in amine-catalyzed hypochlorite bleaching of cellulosic pulps
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date
2024-05
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Language
en
Pages
9
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Cellulose, Volume 31, issue 7, pp. 4043-4051
Abstract
Hypochlorous acid bleaching under amine catalysis (Hcat bleaching stage) is an optimized bleaching stage variant that is characterized by working at weakly acidic, near-neutral pH, having high bleaching efficiency, and discharging only very small amounts of chloro-organics. This study addressed the chemical fate of the used 1,4-diazabicyclo[2.2.2]octane (DABCO) catalyst. While literature proposed either homolytic or heterolytic breakage of one ethylene bridge and subsequent release of the resulting fragments as two molecules of formaldehyde, we demonstrated the degradation to proceed by ionic elimination of one ethylene bridge starting from mono-N-chlorinated DABCO. The resulting N-vinyl (enamine) derivative adds water under the release of acetaldehyde and formation of piperazine. The generation of acetaldehyde was experimentally confirmed by 2,4-dinitrophenylhydrazine trapping, directly from the processing liquid. The experimental findings agreed superbly with computations which showed the “acetaldehyde mechanism” to be much favored over the previously proposed pathways under C–C bond cleavage and release of formaldehyde. The results of this study add to a better understanding of the novel Hcat bleaching system. Graphical abstract: (Figure presented.).Description
We would like to thank the BOKU University, the BOKU doctoral school “Advanced Biorefineries: Chemistry & Materials” (ABC&M), and the county of Lower Austria for their financial support through the framework of the Austrian Biorefinery Center Tulln (ABCT-II). Open access funding provided by University of Natural Resources and Life Sciences Vienna (BOKU). The financial support by the Austrian Biorefinery Center Tulln (ABCT-II) is gratefully acknowledged. The financial support by the GFF Gesellschaft für Forschungsförderung Niederösterreich m.b.H. (A.F.L. and H.H., project LSC20-002) is gratefully acknowledged.
Keywords
Bleaching, Cellulose, Chloramines, DABCO, Elimination reaction, H stage, Hypochlorous acid, Pulp
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Citation
Lehrhofer, A F, Isaza Ferro, E, Hosoya, T, Hettegger, H, Vuorinen, T & Rosenau, T 2024, ' A note on the chemical fate of the DABCO catalyst in amine-catalyzed hypochlorite bleaching of cellulosic pulps ', Cellulose, vol. 31, no. 7, pp. 4043-4051 . https://doi.org/10.1007/s10570-024-05894-w