期刊
CELLULOSE
卷 20, 期 4, 页码 1979-1988出版社
SPRINGER
DOI: 10.1007/s10570-013-9932-4
关键词
Azaadamantane N-oxyl; AZADO; Catalytic oxidation; Nanofibrillation; 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)
资金
- Japan Society for the Promotion of Science (JSPS) [21228007]
- Grants-in-Aid for Scientific Research [21228007] Funding Source: KAKEN
A wood cellulose was oxidized with catalytic amounts of 2-azaadamantane N-oxyl (AZADO) or 1-methyl-AZADO, in an NaBr/NaClO system, in water at pH 10. The oxidation efficiency, carboxylate/aldehyde contents, and degree of polymerization (DPv) of the oxidized celluloses thus obtained were evaluated in terms of the amount of AZADO or 1-methyl-AZADO catalyst added, in comparison with those prepared using the TEMPO/NaBr/NaClO system. When the AZADO/NaBr/NaClO and 1-methyl-AZADO/NaBr/NaClO oxidation systems were applied to wood cellulose using the same molar amount of TEMPO, the oxidation time needed for the preparation of oxidized celluloses with carboxylate contents of 1.2-1.3 mmol/g was reduced from a parts per thousand 80 to 10-15 min. Moreover, the molar amounts of AZADO and 1-methyl-AZADO that had to be added for the preparation of oxidized celluloses with carboxylate contents of 1.2-1.3 mmol/g were reduced to 1/32 and 1/16 of the amount of TEMPO added, respectively. The DPv values for the AZADO- and 1-methyl-AZADO-oxidized celluloses after NaBH4 treatment were in the range of 600-800. This indicated that not only C6-carboxylate groups but also C2/C3 ketones were formed to some extent on the crystalline cellulose microfibril surfaces during the AZADO- and 1-methyl-AZADO-mediated oxidation. When the AZADO-oxidized wood cellulose, which had a carboxylate content of 1.2 mmol/g, was mechanically disintegrated in water, an almost transparent dispersion consisting of individually nano-dispersed oxidized cellulose nanofibrils was obtained, with a nanofibrillation yield of 89 %.
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