Homogeneous alkalization of cellulose in N-methylmorpholine-N-oxide/water solution
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- 作者：Yong Zhang ; Shengwei Tang ; Tao Zhang
- 关键词：Cellulose ; Homogeneous ; Alkalization ; NMMO/H2O system
- 刊名：Cellulose
- 出版年：2017
- 出版时间：March 2017
- 年：2017
- 卷：24
- 期：3
- 页码：1235-1245
- 全文大小：
- 刊物类别：Chemistry and Materials Science
- 刊物主题：Bioorganic Chemistry; Physical Chemistry; Organic Chemistry; Polymer Sciences;
- 出版者：Springer Netherlands
- ISSN：1572-882X
- 卷排序：24
文摘
Alkali cellulose is an important intermediate in the production of cellulose derivatives. N-methylmorpholine-N-oxide (NMMO)/H2O was used as a homogeneous reaction medium for the cellulose alkalization process to intensify the alkalization degree and improve the substitution uniformity. The morphology, specific surface area and crystalline structure of pristine cellulose, the as-synthesized alkali cellulose and dissolved-regenerated cellulose were characterized by SEM, BET, XRD and FT-IR, respectively. The results showed that the homogeneous reaction medium not only offered a low mass transfer resistance, but also facilitated a disruption of the hydrogen bond in cellulose, thus resulting in the transformation of the cellulose structure from complicated stacking chains to simple glucose chains. The interior hydroxyl groups in the cellulose became accessible to the alkaline reagent NaOH to enhance the alkalization process for the increase in bonding alkali content and the improvement in substitution uniformity. The bonding alkali content was calculated by the difference between total added alkali and free alkali and was achieved as 0.61 g/g cellulose at the optimized operation conditions: reaction temperature of 95 °C, reaction time of 90 min, NMMO dosage of 90.00 g, cellulose 1.0 g and NaOH concentration of 1.40 wt%. Meanwhile, in the conventional alkalization process, the bonding alkali content was just 0.41 g/g cellulose. The alkali cellulose prepared in NMMO/H2O medium has a large specific surface area of 125 m2 g−1 and an extremely low crystallinity degree. The NMMO/H2O system represents a potential homogeneous solvent for the cellulose alkalization process.