Abstract
The influence of coexisting salt in 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation of wood cellulose in water at pH 10 for 100 min was investigated, in which Na2SO4 was partly used in place of NaBr in the conventional TEMPO/NaBr/NaClO oxidation system. The amount of NaBr could be reduced from 1 to 0.2 mmol/g-wood cellulose by adding 0.4 mmol/g Na2SO4. This introduced a carboxylate content of ~1.2 mmol/g, which is sufficient to prepare TEMPO-oxidized cellulose nanofibrils (TOCNs) by mechanical disintegration of the oxidized cellulose in water. When no NaBr was used and Na2SO4, Na2SO3, NaCl or CH3COONa was instead used as a coexisting salt in TEMPO/NaClO oxidation, the oxidized celluloses had carboxylate contents of 0.6–0.8 mmol/g, which are insufficient to prepare TOCNs with nanofibrillation yields >55%. The viscosity-average degrees of polymerization of the resulting TEMPO-oxidized celluloses were in the range 420–450, indicating that depolymerization of cellulose is not governed by the carboxylate content of the TEMPO-oxidized cellulose but rather by the oxidation time.
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This research was supported by Core Research for Evolutional Science and Technology (CREST, Grant Number JPMJCR13B2) of the Japan Science and Technology Agency (JST).
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Inamochi, T., Funahashi, R., Nakamura, Y. et al. Effect of coexisting salt on TEMPO-mediated oxidation of wood cellulose for preparation of nanocellulose. Cellulose 24, 4097–4101 (2017). https://doi.org/10.1007/s10570-017-1402-y
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DOI: https://doi.org/10.1007/s10570-017-1402-y