| Summary: | 碩士 === 靜宜大學 === 食品營養研究所 === 99 === Cotton and wood celluloses were subjected to acid degradation in different medias (water, methanol, ethanol, 2-propanol and 1-butanol) at 65 oC for 1-336 h by 1.39% HCl. The recovery, morphology, crystalline structure, molecular characterization of insoluble portion and composition of soluble portion were observed after acid treatment. Results indicated that recovery of cellulose after acid treatment was decreased with increasing treatment time. The recoveries of both celluloses degraded
with alcohols were lower than water, but the recovery of wood cellulose was higher than cotton. Untreated wood cellulose was longer and thinner than cotton, but after acid treatment, both celluloses were shortened following the treatment time even became similar size about 50
μm rod-like microcrystalline cellulose (MCC). Here MCC was obtained from cellulose treated with alcohol was also faster than water. The XRD pattern showed that crystallinity was increased slightly after acid
treatment, but short-term acid treatment would help cellulase to hydrolysis. The weight-average degree of polymerization (DPw) of cotton and wood celluloses had obviously decreased in initial term, and then tended to stable in final. In here, degradation extent and degradation rate of cotton cellulose was faster than wood, and the polydispersity of both celluloses were changed from scatter to focus.
The degradation rate of cellulose treated with different medias were calculated, and had an order of 1-butanol> methanol>> 2-propanol> ethanol> water; crystalline structure and composition of material might affect the degradation and further indicated why cotton was degraded so faster than wood.
After acid treatment, the soluble sugar content was increased with increasing treatment time. The neutral sugar composition of soluble sugar of acid-treated cellulose was analyzed by HPAEC, and glucose was
the major composite ( ＞ 80%) released in solvent from cellulose acid-treated in water, while the content of cellooligosaccharides released in solvent from cellulose acid-treated in alcohols was higher than treated
in water. In this, neutral sugar composition ratio had no relation to alcohol types, but these soluble polymers would be transformed into glucose through longer acid treatment at least.
According to above results, acid treatment of cellulose was
influenced by crystalline structure or composition of cellulose. Cellulose acid-treated in alcohol was more effective than in water and especially treated in methanol. In this, vapor pressure could help acid to penetrate, so methanol might produce vapor pressure in this study (65oC).
Acid-alcohol treatment with high vapor pressure not only increase performance of degradation and shorten treatment time but also avoid recovery decreased, and had good controllability.
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