咪唑类离子液体催化合成正龙脑  

Catalytic synthesis of n-borneol by imidazole ionic liquid

作　　者：黄金艳 杨文娟 蒋丽红[1] 王亚明[1] 郑燕娥 黄鹏鹏 HUANG Jinyan;YANG Wenjuan;JIANG Lihong;WANG Yaming;ZHENG Yan'e;HUANG Pengpeng(Faculty of Chemical Engineering,Kunming University of Science and Technology,Kunming 650500,Yunnan,China)

机构地区：[1]昆明理工大学化学工程学院,云南昆明650500

出　　处：《精细化工》2021年第5期1002-1008,1022,共8页Fine Chemicals

基　　金：国家自然科学基金(21266012);国家自然科学基金联合重点支持项目(U1202265)。

摘　　要：通过两步法合成了4种阴离子不同的咪唑类离子液体,采用FTIR、^(1)HNMR、^(13)CNMR、TG、Hammett酸度函数对其结构和酸度进行表征。以α-蒎烯酯化-皂化反应为探针反应,考察了4种离子液体对正龙脑的选择性。结果表明,阴离子为HSO_(4)^(-)的离子液体对正龙脑的选择性最好,与Hammett酸度函数计算结果吻合。选取[Bmim-SO_(3)H]HSO_(4)做进一步的工艺优化,得到的优化工艺条件为:环己烷用量35 mL,反应温度为120℃,离子液体为松节油质量(10 g)的8%,n(α-蒎烯)∶n(乙酸)=1∶3,反应时间8 h。在该条件下,α-蒎烯的转化率为100%,正龙脑选择性为39.83%,且占总龙脑的92.56%。离子液体提供的H^(+)使α-蒎烯质子化形成碳正离子,HSO_(4)^(-)稳定非经典碳正离子,与乙酸根形成络合物,使生成正龙脑的反应更容易发生。[Bmim-SO_(3)H]HSO_(4)重复使用3次仍具有较高的活性,α-蒎烯的转化率仍达99.76%,正龙脑的选择性为35.45%。Four imidazole ionic liquids with different anions were synthesized by a two-step method. The structure and acidity of ionic liquids were characterized by FTIR, ^(1)HNMR, ^(13)CNMR, TG, Hammett acidity function. The selectivity of four ionic liquids to n-borneol was investigated by using esterificationsaponification reaction of α-pinene as a probe reaction. The result showed that the ionic liquid with an anion of HSO_(4)^(–) had the best selectivity to n-borneol, which was consistent with the result that was calculated by Hammett’s acidity function. The preparation process of n-borneol using [Bmim-SO_(3)H]HSO_(4) as catalyst was optimized. The optimized process conditions were obtained as follows: cyclohexane of 35 m L, reaction temperature of 120 ℃, ionic liquid being 8% of the mass(10 g) of turpentine, n(α-pinene)∶n(acetic acid)=1∶3, reaction time of 8 h. Under these conditions, the conversion rate of α-pinene was 100%, and the selectivity of n-borneol was 39.83%, accounting for 92.56% of the total borneol. H^(+) provide by the ionic liquid protonated α-pinene to form carbocation, HSO_(4)^(-)stabilized non-classical carbocation and formed a complex with acetate, which made the reaction of n-borneol more likely to occur. [Bmim-SO_(3)H]HSO_(4) still had high activity after repeated use for three times, the conversion rate of α-pinene and the selectivity of n-borneol were still 99.76% and 35.45%.

关 键 词：Α-蒎烯 咪唑类离子液体 酯化-皂化 正龙脑 碳正离子 催化技术 

分 类 号：TQ426[化学工程] TQ223.1