Key Laboratory of Interfacial Physics and Technology and Department of Molten Salt Chemistry and Engineering, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Phys Chem Chem Phys. 2021 Sep 22;23(36):20489-20495. doi: 10.1039/d1cp02769g.
As there is a rising interest in upgrading cellulose to high-performance bio-products, the studies on innovative reaction media and processes have been leaping forward. Green solvents in terms of cellulose dissolution and brief processes for upgrading are critical to green chemistry. However, most solvent systems generally exhibit defects in harsh pH operating windows with limited temperature ranges, environmental pollution, long reaction times, complicated processes, In this work, we have provided a novel molten salt hydrate (CaCl·6HO-LiCl) as a green solvent and investigated the role of hydrated molten salts in the dissolution process the solid state nuclear magnetic resonance (NMR) technique. The cellulose could be dissolved in CaCl·6HO-LiCl molten salt hydrated at 120 °C with 3.0% solubility and regenerated in-situ by cooling down to ambient temperature. The regenerated cellulose exhibited a high solubility and excellent stability. From Li single pulse NMR experiments, it was observed that two types of Li existed in the cellulose dissolution, and the Li significantly impacted the dissolving process and the dissolution ability of cellulose. This work would provide an environmental-friendly strategy to prepare cellulose solutions for biocompatible cellulose materials.
由于人们对将纤维素升级为高性能生物制品的兴趣日益浓厚，因此创新反应介质和工艺的研究也在迅速发展。就纤维素溶解和升级的简短过程而言，绿色溶剂对绿色化学至关重要。然而，大多数溶剂体系通常在苛刻的 pH 操作窗口、有限的温度范围、环境污染、长反应时间、复杂的工艺等方面存在缺陷。在这项工作中，我们提供了一种新型的熔融盐水合物（CaCl·6HO-LiCl）作为绿色溶剂，并通过固态核磁共振（NMR）技术研究了水合熔融盐在溶解过程中的作用。纤维素可以在 120°C 下于 CaCl·6HO-LiCl 水合熔融盐中以 3.0%的溶解度溶解，并通过冷却至环境温度原位再生。再生纤维素表现出高溶解度和优异的稳定性。通过 Li 单脉冲 NMR 实验，观察到两种类型的 Li 存在于纤维素的溶解中，Li 显著影响溶解过程和纤维素的溶解能力。这项工作将为制备用于生物相容纤维素材料的纤维素溶液提供一种环保策略。
