[BMIm]Br离子液体辅助HZSM-5催化乙酸环己酯高选择性水解反应

为提高HZSM-5催化乙酸环己酯水解反应生成环己醇的选择性，筛选得到了离子液体BMIm]Br助剂。发现BMIm]Br可抑制乙酸环己酯热分解副反应的发生，大幅度提高环己醇选择性。并且，BMIm]Br可与HZSM-5发生离子交换反应，释放出的H⁺可促进乙酸环己酯水解反应的发生。在优化的条件下，BMIm]Br辅助HZSM-5催化乙酸环己酯水解反应转化率为87.5%，环己醇选择性为97.3%。考察了BMIm]Br和HZSM-5的重复使用性。前者具有较好的稳定性，而HZSM-5活性随循环使用的次数增加而下降。这是由于HZSM-5的骨架铝含量在反应中逐渐降低，导致Br?nsted酸中心数量减少，因此其催化活性逐渐降低。

Highly selective hydrolyzation of cyclohexyl acetate over HZSM-5 assisted by [BMIm]Br ionic liquid

To improve the selectivity of HZSM-5 to catalyze the hydrolysis reaction of cyclohexyl acetate to cyclohexanol, an ionic liquid BMIm]Br auxiliary was screened. It was found that BMIm]Br could inhibit the side-reaction, thermal decomposition of cyclohexyl acetate, and increase the selectivity to cyclohexanol greatly. Moreover, the ion exchange between BMIm]Br and HZSM-5 could promote the generation of H⁺, which could accelerate the hydrolyzation of cyclohexyl acetate. Under the optimized reaction conditions, cyclohexyl acetate conversion was 87.5% with 97.3% cyclohexanol selectivity over HZSM-5 assisted by BMIm]Br. The reusability of BMIm]Br and HZSM-5 was investigated respectively, and the former exhibited good stability. However, the catalytic activity of HZSM-5 decreased gradually with the recycling times. It was due to the decreasing of framework Al content of HZSM-5 during the reaction, which led to the reduction of Br?nsted acid sites and therefore resulted in the decreased activity.