| Summary: | 碩士 === 國立中央大學 === 化學學系 === 107 === In this study, recrystallization of amorphous cellulose has been discovered in the homogeneous hydrolytic depolymerization with relatively high saccharide concentration (2.5 wt%) and low catalytic ratio for acidic hydrolysis (4.87 mol%) at various reaction temperatures. The cellulosic residues collected after aforementioned acid hydrolysis were characterized by powder X-ray diffraction (PXRD) as well as gel-permeation chromatography (GPC). The PXRD study revealed the trend of structural transformation for amorphous cellulose to recrystallized cellulose escalated during hydrolysis, while elevating reaction temperature from 130oC to 210oC. In addition, GPC study suggested that weight average molecular mass (Mw) centering around 6,500 Da exhibited similar distribution after hydrolytic depolymerization while elevating reaction temperature from 170oC-210oC. These observations above indicated that recrystallization of amorphous cellulose indeed took place to impede the depolymerization during acid hydrolysis. In addition, judging from the correlation between the average molecular weight and the crystallinity index of recrystallized amorphous polysaccharides, we have found that shorter cellulosic polymer exhibited higher degree of recrystallization during hydrolytic depolymerization which might lead to understand better to design efficient catalysts for hydrolytic depolymerization of polysaccharides in the future. On the other hand, the dynamic study of the hydrolysis of amorphous cellulose shows that both cellulose I and cellulose II have their own preferable forming condition, from which we found that controlling the reaction temperature might play a key role to produce a single allomorph of cellulose. This might lead us to study further about the kinetics and thermodynamics behind the formation of the allomorphs of cellulose.
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