Preparation and Application of CO2-Triggered Switchable Solvents in Separation of Toluene/n-Heptane
Preparation and Application of CO2-Triggered Switchable Solvents in Separation of Toluene/n-Heptane
复制标题
CO2触发可转换溶剂的制备及其在甲苯/正庚烷分离中的应用
DOI：
10.1021/acs.langmuir.9b02890
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发表时间：
2020
期刊：
影响因子：
3.9
通讯作者：
Ren Zhongqi
中科院分区：
文献类型：
--
作者：
Zhang Zidong;Tu Yuming;Yu Hui;Liu Weidong;Zhou Zhiyong;Ren Zhongqi
萃取是分离芳烃和烷烃的常用方法，但溶剂回收仍然是一个问题。在各种触发条件下，可切换溶剂的极性、疏水/亲水平衡和其他性质可以可逆地改变，利用这一性质可以大大简化溶剂回收的过程。在这项工作中，利用季铵盐和阴离子交换，将oh离子引入到脒类化合物1,8-重氮双环[5.4.0]十一-7-烯（DBU）的衍生物中，制备了几种可切换的溶剂。所得到的化合物在暴露于二氧化碳时表现出可逆的转换反应。以甲苯/正庚烷为模型烃类混合物，建立了可逆相变萃取工艺。在制备的4种可切换溶剂中，[C2DBU]OH表现出最高的选择性值，因此研究了不同参数对烃类分离的影响。当co2通过萃取混合物冒泡生成两相体系时，发现萃取过程迅速达到平衡。增加溶剂的比例可以提高对甲苯的选择性，当溶剂与甲苯/正庚烷混合物的比例为1:1时，萃取效果更好。增加初始甲苯浓度降低了甲苯的选择性，在甲苯浓度为20%时，甲苯的选择性为5.97。在60℃下加热1 h后，可切换溶剂恢复到初始状态。在去除CO2后重复使用时，溶剂表现出较差的分离特性，尽管在10次再生中选择系数保持在3.1左右不变。最后，对溶剂转换效应的机理和实验数据的建模进行了研究。
Extraction is a common approach to separating aromatics and alkanes, but solvent recovery remains an issue. The polarity, hydrophobic/hydrophilic balance, and other properties of switchable solvents can be reversibly changed in the presence of various triggers, and taking advantage of this property can greatly simplify the process of solvent recovery. In this work, quaternation and anion exchange were used to prepare several switchable solvents by introducing OH–ions to derivatives of the amidine compound 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). The resulting compounds exhibited reversible switching in response to exposure to CO2. Using toluene/n-heptane as a model hydrocarbon mixture, a reversible phase change extraction process was established. Among the four switchable solvents prepared, [C2DBU]OH showed the highest selectivity value and so was used to investigate the effect of various parameters on hydrocarbon separation. The extraction process was found to rapidly reach equilibrium when a two-phase system was generated by bubbling CO2through the extraction mixture. Increasing the proportion of the solvent increased the selectivity for toluene, while a 1:1 ratio between the solvent and the toluene/n-heptane mixture enhanced the extraction. Increasing the initial toluene concentration reduced the selectivity for toluene, with a value of 5.97 at a toluene concentration of 20%. The switchable solvent recovered its initial state when heated at 60 °C for 1 h. Upon being reused after removal of CO2, the solvent exhibited poor separation characteristics, although the selectivity coefficient remained constant at approximately 3.1 during 10 regenerations. Finally, the mechanism of the switchable solvent effect and modeling of experimental data were investigated.