The swelling and dissolution of cellulose crystallites in subcritical and supercritical water
The swelling and dissolution of cellulose crystallites in subcritical and supercritical water
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DOI：
10.1007/s10570-013-0072-7
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发表时间：
2013-10
期刊：
影响因子：
5.7
通讯作者：
Lasse K Tolonen;P. Penttilä;R. Serimaa;A. Kruse;H. Sixta
中科院分区：
文献类型：
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作者：
Lasse K Tolonen;P. Penttilä;R. Serimaa;A. Kruse;H. Sixta
研究了微晶纤维素（MCC）在亚临界和超临界水中的溶胀和溶解现象。将商业MCC在250-380 °C的温度和250巴的压力下在水中处理0.25-0.75秒。作为反应产物，检测到未溶解但解聚的纤维素残留物、短链纤维素沉淀物、水溶性纤维低聚糖和单糖以及它们的降解产物。在360 °C下反应0.25 s后，获得纤维素II沉淀物的最高产率。我们的假设是，如果微晶溶胀，解聚模式将是均相反应，并观察到纤维素Iβ向纤维素II的转化。未溶解的纤维素残留物的结构的变化，其特征在于通过尺寸排阻色谱，广角X射线散射和13 C固态NMR技术。在许多情况下，纤维素残留物样品中含有纤维素II;然而，由于实验限制，尚不清楚它是通过微晶溶胀还是溶解的纤维素部分的部分再吸附形成的。未处理的MCC和低强度处理后的MCC的摩尔质量分布呈双峰形状。在高强度处理后，高摩尔质量链消失，这表明微晶完全溶胀或溶解。
The swelling and dissolution phenomena of microcrystalline cellulose (MCC) were investigated in subcritical and supercritical water. Commercial MCC was treated in water at temperatures of 250–380 °C and a pressure of 250 bar for 0.25–0.75 s. As reaction products, undissolved but depolymerised cellulose residue, short-chain cellulose precipitate, water-soluble cello-oligosaccharides and monosaccharides, as well as their degradation products, were detected. The highest yield of the cellulose II precipitate was obtained after a reaction time of 0.25 s at 360 °C. Our hypothesis was that if the crystallites were swollen, the depolymerization pattern would be that of homogeneous reaction and the cellulose Iβ to cellulose II transformation would be observed. The changes in the structure of the undissolved cellulose residue were characterised by size exclusion chromatography, wide-angle X-ray scattering and13C solid-state NMR techniques. In many cases, the cellulose residue samples contained cellulose II; however, due to experimental limitations, it remains unclear whether it was formed through the swelling of crystallites or the partial readsorption of the dissolved cellulose fraction. The molar mass distributions of untreated MCC and after low intensity treatments showed a bimodal shape. After high intensity treatments the high molar mass chains disappeared which indicated a complete swelling or dissolution of the crystallites.