双咪唑环离子液体的制备及其正己烷异构化性能

设计合成了3种分别含甲基、乙基和丁基取代基的双咪唑环离子液体前驱体M₁、M₂和M₃，并对其进行核磁共振(¹H NMR和¹³C NMR)、高分辨质谱(ESI-MS)和同步热分析(TG/DTG/DSC)等表征。基于前驱体M₁、M₂和M₃合成了一系列双咪唑环离子液体催化剂AlCl₃/M₁、AlCl₃/M₂和AlCl₃/M₃，利用紫外-可见光谱(UV-visible)和乙腈红外(CAN-IR)表征方法对其酸性进行了研究。在此基础上研究取代基对正己烷异构化性能的影响并优化其反应工艺条件。结果表明：乙基为取代基的双咪唑环离子液体所合成的催化剂AlCl₃/M₂具有较多的BrÖnsted酸和Lewis酸位，有助于异构化反应的进行；在AlCl₃与前驱体M₂中Cl^-的摩尔比为2.1∶1、反应温度30 ℃、反应时间10 h和剂/油质量比1∶1的最佳工艺条件下，正己烷转化率为74.52%，异己烷选择性和收率分别为29.51%和21.99%。

Synthesis of Bisimidazole Ring Ionic Liquids and Their n-Hexane Isomerization Performance

Three bisimidazole ring ionic liquid precursors M₁, M₂ and M₃ containing methyl, ethyl and butyl substituents were synthesized and characterized by ¹H NMR, ¹³C NMR, ESI-MS and TG/DTG/DSC. A series of bisimidazole ring ionic liquid catalysts AlCl₃/M₁, AlCl₃/M₂ and AlCl₃/M₃were synthesized based on the corresponding precursors M₁, M₂ and M₃, and their acidity was studied using UV-visible and acetonitrile IR (CAN-IR) characterization methods. Furthermore, the effect of substituents on the isomerization performance of n-hexane was studied, and its reaction process conditions were also optimized. The results shows that the catalyst AlCl₃/M₂ synthesized by bisimidazole ring ionic liquid with ethyl as the substituent has more BrÖnsted and Lewis acid sites, which is helpful for the isomerization reaction. Under the optimal process conditions: molar ratio of AlCl₃ to Cl^-  (2.1∶1) in the precursor M₂, reaction temperature of 30 ℃, reaction time of 10 h and mass ratio of catalyst to oil (1∶1), the n-hexane conversion rate is 74.52%, and the selectivity and yield of isohexane are 29.51% and 21.99%, respectively.