Abstract:

Trans-1,2-cyclohexanediol was synthesized by the oxidation of cyclohexene using H2O2 as the oxidant and ionic liquids(ILs) as the catalyst and solvent. The effects of different imidazolium ionic liquids, reaction time, reaction temperature and the amount of H2O2 on the yield and selectivity of trans-1,2-cyclohexanediol were investigated. The experimental results showed that ionic liquids based on imidazolium cations containing 1~2 carboxyl groups and [PF6] anion exhibited the highest catalytic activities among the seven imidazolium ionic liquids. Under optimized conditions: reaction temperature 100 ℃, n(H2O2)∶n(cyclohexene)=1.1∶1, and reaction time 5 h, the yield and selectivity of trans-1,2-cyclohexanediol were 95% and 97% with IL c(0.60 g, 2.1 mmol) as the catalyst, and 84% and 90% with IL f(0.20 g, 0.6 mmol) as the catalyst, respectively. From the dosage of ionic liquid, it can be seen the catalytic efficiency of IL f containing two carboxyl groups was higher.

Key words: ionic liquids, cyclohexene, Peroxide, trans-cyclohexanediol