Continuous production of cellulose mixed esters via homogeneous reactive twin-screw extrusion catalyzed by ionic liquid
Continuous production of cellulose mixed esters via homogeneous reactive twin-screw extrusion catalyzed by ionic liquid
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DOI：
10.1007/s10570-023-05062-6
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发表时间：
2023-02-02
期刊：
影响因子：
5.7
通讯作者：
Takahashi, Kenji
中科院分区：
文献类型：
--
作者：
Hernandez, Stephanie C.;Milotskyi, Romain;Takahashi, Kenji
由两种不同类型的酰基取代的纤维素混合酯(CME)是一种具有多种可调性能的聚合物材料，但制备难度较大。这是因为纤维素在普通溶剂中不溶，因此，工业生产具有所需取代度(DSS)的CMES需要一个昂贵的多步骤过程。为了实现它们的简便生产，使用离子液体(ILS)作为纤维素的溶剂进行了均相反应。然而，纤维素-IL溶液的高粘度导致间歇反应器中的混合不足；因此，有利于较低的纤维素浓度和较长的反应时间(通常为数小时)。在这里，我们展示了一种通过利用双螺杆挤出机的优良剪切混合作为流动反应器来快速和可扩展地生产CME的方法。采用由IL、1-乙基-3-甲基咪唑乙酸酯和二甲基亚砜组成的共溶剂体系，通过双螺杆挤压法溶解高浓度(15wt.%)的纤维素。在80℃的连续挤压过程中，纤维素与乙酸异丙烯(IPAC)和丙酸乙烯酯(VPR)(2.5：0.5，摩尔/摩尔)两种酰基试剂在几分钟内反应生成醋酸丙酸酯(CAP)。在50min的操作时间内，CAP的产量稳定，平均分离率为71%。CAP的乙酰基和丙酰基的DSS分别为1.77和0.50，相当于IPAC和VPR的高转化率，分别为70%和100%。
Cellulose mixed esters (CMEs) substituted with two different types of acyl groups are promising polymeric materials with various tunable properties but are arduous to produce. This is because of the insolubility of cellulose in common solvents, and thus, the industrial production of CMEs with desired degrees of substitution (DSs) requires a costly multistep process. To accomplish their facile production, homogeneous reactions have been performed using ionic liquids (ILs) as solvents for cellulose. However, the high viscosity of the cellulose-IL solutions causes insufficient mixing in batch reactors; thereby, favoring low cellulose concentrations with long reaction times (typically hours). Herein, we demonstrate a rapid and scalable production of CMEs by exploiting the excellent shear mixing of a twin-screw extruder as a flow reactor. A co-solvent system comprising an IL, 1-ethyl-3-methylimidazolium acetate, and dimethyl sulfoxide was applied to dissolve cellulose at a high concentration (15 wt.%) via twin-screw extrusion. During continuous extrusion at 80 degrees C, cellulose reacted with two acyl reagents, isopropenyl acetate (IPAc) and vinyl propionate (VPr) (2.5:0.5, mol/mol), to yield cellulose acetate propionate (CAP) within minutes. The CAP was stably produced during the operation time of 50 min with an average isolated yield of 71%. The DSs of the acetyl and propionyl groups of CAP were 1.77 and 0.50, respectively, corresponding to sufficiently high conversion rates of 70% for IPAc and 100% for VPr.