蔗渣大分子半纤维素和纳米纤维素的一体式全制备

Integrated Preparation of Hemicellulose Macromolecular and Nanocellulose from Bagasse

使用质量分数4%~20%的NaOH溶液预处理蔗渣,以33.5%~73.1%的较高得率获得了平均分子质量为40~60 kDa的大分子半纤维素,然后采用2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)氧化法,在没有额外机械力作用下,将抽提后的残渣成功转化成直径小于15 nm、长度几十纳米至2μm且分散性很好的TEMPO氧化纤维素纳米晶体(TOCN)。研究还发现,NaOH预处理不但可以有效地从蔗渣中提取半纤维素,而且明显提高了TEMPO氧化法制备纳米纤维素的效率。传统TEMPO氧化纤维原料需机械处理且只能制备CNF,而本研究通过NaOH预处理协同TEMPO氧化法,无需机械处理即可得到具有较好尺寸的CNC。另外,预处理所用碱浓的增加导致纤维素的晶型发生转变,且随着预处理时间的延长,其发生转变时所需的碱浓降低。

Hemicellulose macromolecular with an average molecular mass of 40~60 kDa was obtained with a high yield of 33.5%~73.1% from the bagasse pretreated by 4%~20% NaOH solution.Subsequently,well-dispersed TEMPO oxidized cellulose nanocrystal(TOCN)with diameter less than 15 nm and length in the range of tens of nanometers to 2μm was prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated(TEMPO)oxidation without extra mechanical treatment.The results showed that the NaOH pretreatment not only effectively extracted hemicellulose from bagasse,but also enhanced the preparation efficiency of nanocellulose via TEMPO oxidation.Traditional TEMPO oxidized fiber raw materials with mechanical treatment could only produce CNF.TOCN with good size could be obtained through NaOH pretreatment and TEMPO oxidation without mechanical treatment in this study.In addition,the increase of the alkali concentration used in the pretreatment resulted in the change of the cellulose crystalline allomorph.With the pretreatment time increased,the alkali concentration was decreased during crystalline allomorph transformation.