Reaction engineering implications of cellulose crystallinity and water-promoted recrystallization†,Green Chemistry

当前位置： X-MOL 学术 › Green Chem. › 论文详情

Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)

Reaction engineering implications of cellulose crystallinity and water-promoted recrystallization†
Green Chemistry ( IF 9.3 ) Pub Date : 2019-09-24 , DOI: 10.1039/c9gc02466b
Maksim Tyufekchiev _{1,

2,

3,

4} , Alex Kolodziejczak _{1,

2,

3,

4} , Pu Duan _{4,

5,

6,

7} , Marcus Foston _{4,

8,

9,

10,

11} , Klaus Schmidt-Rohr _{4,

5,

6,

7} , Michael T. Timko _{1,

2,

3,

4}

Affiliation

Mechanical decrystallization and water-promoted recrystallization of cellulose were studied to understand the effects of cellulose crystallinity on reaction engineering models of its acid-catalyzed hydrolysis. Microcrystalline cellulose was ball-milled for different periods of time, which decreased its crystallinity and increased the glucose yield obtained from acid hydrolysis treatment. Crystallinity increased after acid hydrolysis treatment, which has previously been explained in terms of rapid hydrolysis of amorphous cellulose, despite conflicting evidence of solvent promoted recrystallization. To elucidate the mechanism, decrystallized samples were subjected to various non-hydrolyzing treatments involving water exposure. Interestingly, all non-hydrolyzing hydrothermal treatments resulted in recovery of crystallinity, including a treatment consisting of heat-up and quenching that was selected as a way to estimate the crystallinity at the onset of hydrolysis. Therefore, the proposed mechanism involving rapid hydrolysis of amorphous cellulose must be incomplete, since the recrystallization rate of amorphous cellulose is greater than the hydrolysis rate. Several techniques (solid-state nuclear magnetic resonance, X-ray diffraction, and Raman spectroscopy) were used to establish that water contact promotes conversion of amorphous cellulose to a mixture of crystalline cellulose I and cellulose II. Crystallite size may also be reduced by the decrystallization-recrystallization treatment. Ethanolysis was used to confirm that the reactivity of the cellulose I/cellulose II mixture is distinct from that of truly amorphous cellulose. These results strongly point to a revised, more realistic model of hydrolysis of mechanically decrystallized cellulose, involving recrystallization and hydrolysis of the cellulose I/cellulose II mixture.

中文翻译：

纤维素结晶度和水促进的重结晶的反应工程意义†

研究了纤维素的机械去结晶和水促进的重结晶过程，以了解纤维素结晶度对其酸催化水解反应工程模型的影响。将微晶纤维素球磨不同的时间，这会降低其结晶度并增加酸水解处理获得的葡萄糖收率。酸水解处理后结晶度增加，尽管有证据表明溶剂促进了重结晶，但先前已经用无定形纤维素的快速水解进行了解释。为了阐明机理，对脱结晶的样品进行了各种非水解处理，其中包括暴露于水。有趣的是，所有非水解水热处理都会恢复结晶度，包括由加热和淬灭组成的处理，该处理被选择为评估水解开始时的结晶度的方法。因此，由于无定形纤维素的重结晶速率大于水解速率，因此所提出的涉及无定形纤维素的快速水解的机理必须是不完整的。几种技术（固态核磁共振，X射线衍射和拉曼光谱法）用于确定水接触可促进无定形纤维素转化为结晶纤维素I和纤维素II的混合物。微晶尺寸也可以通过去结晶-再结晶处理来减小。乙醇水解用于证实纤维素I /纤维素II混合物的反应性与真正无定形纤维素的反应性不同。

更新日期：2019-10-14

点击分享查看原文

点击收藏

阅读更多本刊新发论文本刊介绍/投稿指南