Department of Forest Product Technology, School of Chemical Technology, Aalto University, Helsinki, Finland.
Biomacromolecules. 2011 Jul 11;12(7):2544-51. doi: 10.1021/bm200351y. Epub 2011 Jun 6.
Subcritical water is a high potential green chemical for the hydrolysis of cellulose. In this study microcrystalline cellulose was treated in subcritical water to study structural changes of the cellulose residues. The alterations in particle size and appearance were studied by scanning electron microscopy (SEM) and those in the degree of polymerization (DP) and molar mass distributions by gel permeation chromatography (GPC). Further, changes in crystallinity and crystallite dimensions were quantified by wide-angle X-ray scattering and (13)C solid-state NMR. The results showed that the crystallinity remained practically unchanged throughout the treatment, whereas the size of the remaining cellulose crystallites increased. Microcrystalline cellulose underwent significant depolymerization in subcritical water. However, depolymerization leveled off at a relatively high degree of polymerization. The molar mass distributions of the residues showed a bimodal form. We infer that cellulose gets dissolved in subcritical water only after extensive depolymerization.
亚临界水是一种有很大潜力的绿色化学物质，可用于纤维素的水解。在这项研究中，微晶纤维素在亚临界水中进行处理，以研究纤维素残留物的结构变化。通过扫描电子显微镜（SEM）研究了颗粒尺寸和外观的变化，通过凝胶渗透色谱（GPC）研究了聚合度（DP）和摩尔质量分布的变化。此外，还通过广角 X 射线散射和（13）C 固态 NMR 定量了结晶度和微晶尺寸的变化。结果表明，在整个处理过程中，结晶度几乎保持不变，而剩余纤维素微晶的尺寸增大。微晶纤维素在亚临界水中经历了显著的解聚。然而，解聚水平在相对较高的聚合度时趋于稳定。残留物的摩尔质量分布呈双峰形式。我们推断，只有在纤维素经历了广泛的解聚后，它才会在亚临界水中溶解。
